Surviving a Cold Snap

Surviving a Cold Snap

Surviving a Cold Snap

15 minute read –
This is Part 3 of a 4 part series by guest author and ecologist, Joshua Robertson on how wildlife at the Yukon Wildlife Preserve stays warm (thermoregulates) in the winter. Read Part 1: Staying Warm in the Yukon and Part 2: Winter Heat Losses.


A few weeks ago, my partner and I had the beautiful fortune to welcome a baby into our family. For me (and my partner), the birth of this baby has meant stepping into the joyous and mystifying waters of parenthood for the very first time. Quite simply, we’re exhilarated. And like most first-time parents, we’re also, perhaps, a touch naive. Despite months of preparative reading and numerous discussions with other early parents, hardly a few hours had passed after his birth when questions began to percolate. How long should feedings last? Is co-sleeping preferable to sleeping separately? And the question most influenced by my career biases: how can we tell if our baby is sufficiently warm, or overheating?

Josh standing outside in snow with his new baby.
Upon realising the absolute dependence of our child on external help, the last of these questions noticeably shook me. For many years, I had viewed thermoregulation through an admittedly narrow lens. I contextualised the costs of warming and cooling in endotherms as manageable. True, I had acknowledged that such costs were often substantial, but I also coloured this acknowledgement with an all-too-human optimism bias. For example, crossbills can spend enormous amounts of energy on warming in the winter (often doubling their energy expenditure from summer to winter), but we still see crossbills persisting regularly through the worst of the season. So, my subconscious told me, why not ignore the situations where managing costs of warming isn’t possible?
Curiously, facing the decision of how to clothe our child allowed me to temporarily silence certain optimism biases. The costs of clothing him improperly, and thus challenging his capacity to thermoregulate, were simply too large to ignore; they could mean losing him. To me, this was a rather disquieting thought. Yet the lethal toll of poor thermoregulation is what all warm-blooded animals (or “endotherms”) must face, and have faced, since their evolution millions of years ago. (Of course, a similar toll can apply to many cold-blooded animals, or “ectotherms”, that rely on thermoregulatory behaviours, such as sun-bathing, to survive). How equally disquieting!
Photo of crossbill foraging.
But why stew on such bleak thoughts at all? Why begin our discussion in this way? Well, in my opinion, doing so leads us to two interesting and useful conclusions:

  1. Extreme cold and extreme heat for many animals can be, and often is, a real threat to their survival, and,
  2. Facing this threat has paved the way for the evolution of some truly spectacular thermoregulatory strategies and capacities.

Evolution can be a brutal, yet wonderful process.

Thermoregulating in a Cold Snap

In this post, we’ll be taking a look at how certain endotherms at the Yukon Wildlife Preserve are challenged by cold snaps that would undoubtedly prove lethal to an unprepared human. In doing so, we’ll also take a look at how these animals compare to one another in their thermoregulatory strategies and capacities. If you’re like me, I think you’ll find the conclusions intriguing. So let’s put aside the sombre tone and see what findings emerge.

Now if you happened to read my last post (Winter Heat Losses), you’ll recall that to understand the costs of thermoregulation across certain Yukon-dwellers, Jake Paleczny (our Executive Director) and myself braved the January cold to capture infrared thermographic images of animals cared for at the Yukon Wildlife Preserve. With these images, we were able to quantify just how much heat animals were losing to the environment, and thereafter, estimate how much energy these animals would need to spend to compensate for their heat-loss. In doing so, we discovered that at -12°C, the average Moose might spend slightly less than one McDonald’s cheeseburger worth of energy on warming across a 4 hour period. By contrast, the average Thinhorn Sheep (or “Dall Sheep”) might spend about one and three quarters cheeseburgers in similar circumstances, and the average Muskox, around negative one half of a cheeseburger. And where did Jake fit in? We estimated his expenditure to be about one cheeseburger, despite wearing full winter gear. To top these findings off, we also discovered that if we were to scale the costs of warming according to usual daily energy expenditure in each animal, Jake would probably be spending more than each of the other observed animals on warming. All together, I’d say that these are some interesting findings. But remember, our observations were made at -12°C – hardly a real thermal challenge for Yukon natives (particularly for those in Old Crow, where record lows have reached nearly -60°C).
So what happens to costs of thermoregulation when a true challenge strikes? For example, what do costs of warming look like when temperatures fall below -30°C, as they did in Whitehorse during early February?  Below, I’ll do my best to answer that question. But first, I think it’s important that I remove some turbidity from our discussion. In our past discussion, my estimates of cheeseburger-use across animals were about as opaque as the Liard River. Indeed, some of you were likely wondering how such estimates were made at all, and how they might be prone to error. These are good things to wonder. So how were our estimates made after all? If the answer to that question doesn’t interest you, I’d recommend you skip a few paragraphs to get to our final findings below. For those who are interested, the next few paragraphs detail the path that myself (and other thermal biologists) would typically walk to understand how an animal is interacting with, and adjusting to, their thermal environment. A detailed description can also be found in one of my recent publications about black-capped chickadees.

Estimating the Cost of Thermoregulation

Before I begin, I’ll be honest and state that the manner by which I’ve estimated costs of thermoregulation may seem more convoluted than necessary. Actually, in some ways, it probably is more convoluted than necessary. But it does reflect standard practice in the field of thermal biology (for good reason), and it does provide opportunities to paint a fuller picture of what is happening across an animal at the time that an infra-red thermographic picture was captured. With that in mind let’s begin.

Thermal image of Thinhorn Sheep at 34c below 0c. Scale is in rads.
Let’s first return to an image of a handsome male Thinhorn Sheep, captured at -12°C (shown above). First, have a look at the scale bar on the top right of the image. You’ll notice that the range of values has changed substantially from those in our previous images. That’s because these values now represent the amount of infrared radiation (specifically, a subset of infrared radiation referred to as “long-wave” radiation) that the camera has detected at each pixel. Notice that these values are not in degrees Celsius, nor are they in any other unit of temperature. Rather, they represent units of energy per area (possibly kilowatts per meter squared, or “kW/m2”, however, the actual units are not disclosed by the camera producer). Remember, heat has the capacity to do work, so it can be measured in units of energy.  These values in kW/m2 are precisely what our infrared thermographic camera gives us – the next step is to figure out what they really mean for a specific object (our sheep).
Line drawing of energy sources and losses when taking thermal images.
To make sense of our energy measurements, we first need to acknowledge that the infra-red radiation striking our camera can come from a number of sources: our sheep, the molecules in the atmosphere, and, of course, the sun (either travelling directly to our camera, or by reflection from other objects like the surrounding snow or the sheep’s pelage). Furthermore, some of the infra-red radiation travelling toward our camera can, and will be, absorbed by molecules in the air (like water vapour) before reaching us. This means that if we wish to make any inferences about heat-loss from our sheep (indicated by the teal arrow in the diagram above), we’ll need to control for the heat produced by the sun and the environment, the amount of water vapour in the air, and the reflective capacity of the sheep’s fur. Thankfully, we can make pretty good guesses at these factors by looking at the temperature and humidity at the time we captured our image, and by drawing on measurements of fur reflectance in other animals. Once we’ve controlled for these values and followed what’s called “Planck’s Law”, we’re left with the beautiful image below.
Thermal image of Thinhorn Sheep at 12c below 0c. Scale is in degrees.
Notice that the values are now in units of temperature? A pretty good step forward!

Now what about the costs of heat-loss? To estimate this value, a little more calculation will be required. First, you may recall from high-school physics class that heat can be lost in any of three ways: conduction, convection, and radiation. The first method describes the transfer of heat from a solid object to another solid object (think of your lap after being warmed by a cat). By contrast, the other two methods described transfer of heat from a solid to a fluid, and to empty space (think of your hands after warming them by the fire). Estimating heat-loss by each method requires the use of several biophysical theories and equations (nicely summarised by Dominic McCafferty and others), but there are a few common and convenient threads running through them. For example, calculating heat-loss by each method requires knowledge of:

  1. The temperature differential; that is, how big the temperature difference is between the warm object and the “thing” that it is losing heat to,
  2. Resistance; that is, how much an object opposes heat flow (this value factors into properties of an object called the “heat transfer coefficient”, or “thermal conductivity”), and,
  3. Surface area; that is, how much space there is for heat to transfer between a solid object and the “things” it is in contact with.

If we think about it breifly, these values, or parameters, are actually quite intuitive. Big temperature differentials, like those Jake experienced between his body and the air, mean big heat losses. Similarly, low resistance and a large surface area, like those experienced by our large and poorly-insulated moose, also mean big heat losses. For our calculations of heat-loss, we can make strong guesses at resistance and temperature differential values by looking at previous studies on heat emission from biological tissues, and by – you guessed it – using the temperature values that we obtained from our thermal images.

But what about surface area? Now here’s where things can turn sour. Measuring the surface area of an animal can be extremely difficult, especially since the body shape of most animals hardly represents a simple geometrical shape. (As a quick thought experiment, imagine measuring the surface area of a human ear). This, then, is where error around our cheeseburger estimates mostly come in. Why? Because the best we can do is approximate with some simple shapes that are drawn to match known animal measurements – like in the image below.
Line drawing showing a sheep being represented by simple shapes for surface area estimation.
These approximations work, but aren’t perfect; that is, you could probably guess that the figure on the right is a sheep, but it certainly wouldn’t pass as one to another sheep (although if we were talking about poultry, the story might be different). With that in mind, I wouldn’t recommend betting a limb on our cheeseburger estimates. While our estimates likely do draw close to the true values we’d see in nature, they will, admittedly, stray by some moderate degree. This source of error is one that has plagued thermal biologists for quite some time, and even the more complex models still usually represent mammals as furry tubes (for example, see Porter and Kearney, 2009)
Now that we’ve cleared the Liard, let’s get back to heat-loss at the preserve during our cold snap.  Remember, we’re looking at how animals respond to temperatures below -30°C. Care to guess what this means for our temperature differentials?

Moose and Muskox at -34°c

To begin, let’s revisit a few candidates from last week: the Moose and Muskox (depicted below). Sadly, we weren’t able to capture any images of the Thinhorn Sheep during the cold snap, so we’ll have to leave that species to our imagination for today.

If you recall from our previous discussion, our Moose and Muskox spent around one, and negative one-half cheeseburgers worth of energy on keeping warm at -12°C across four hours. So what does their expenditure look like during a true cold snap?
For the Moose, quite a bit different. At -34°C, our imaged Moose is likely spending about two whole  cheeseburgers on maintaining a constant body temperature across a four hour period. That’s a little over a two-fold increase from their expenditure at -12°C. As you can imagine, two whole cheeseburgers is quite a bit of energy to spend on warming, particularly when that energy is sourced from sparse patches of foliage. In nearby Alaska, Moose largely subsist on the twigs of various willow species throughout the winter months, including Feltleaf Willow, Diamondleaf Willow, and Greyleaf Willow (see Risenhoover, 1989). Surprisingly, previous studies have shown that Moose are able to extract a fairly high amount of energy from the tissue of these plants: approximately 5 calories/gram, or about the calorie density of mayonnaise for us humans. Nevertheless, at this calorie density, compensating for the energy needed to keep warm on a -34°C day would require our Moose to consume over half of a kilogram more plant tissue than usual. To put this value into perspective, that’s about all of the willow twigs in a 20 – 65 square meter area of suitable browsing habitat (which can be patchy in some places).
Line drawing showing a sheep being represented by simple shapes for surface area estimation.
If temperatures this low persisted for a long period of time (say, weeks), and suitable browse can’t be found, they could represent a very real threat to a Moose’s survivorship – particularly if energy is also being spent on evading possible predators. As we’ll see shortly, however, the degree of this threat actually pales in comparison to that faced by other, less equipped animals. But for now, what about our Muskox?
Amazingly, the amount of energy spent on warming in Muskox at -12 and -34°C remains virtually unchanged. In fact, our estimate suggests that our imaged Muskox is probably spending little to no extra energy on warming at -34°C, relative to average energy expenditure! If you find this result surprising (as I have), you’re not alone. In 2009, Munn and others obtained very similar results when monitoring Muskox in Alaska, and like us, express their appreciation. They quote:

Surface temperatures of muskoxen were only 5°C above ambient temperatures at -30°C, a testament to the substantial insulation provided by their coat…”

Okay, appreciation might be a strong word, but the above quote is probably the closest one can get to appreciation in terse scientific language.

Caribou and Arctic Fox: Cold Weather Specialists

So what about some other Yukon residents? And what about Jake? Next, let’s have a look at few other winter specialists: the Woodland Caribou and Arctic Fox (shown in the images below).

From a quick glance at the image of our Caribou (on the left), we can already guess that thermoregulatory expenditure is this male is probably going to fall below that of the Moose. This makes sense, given that the Caribou “species complex” (that is, the aggregation of all Caribou variants) regularly ranges further north than the Moose. Moreover, Moose are thought to be relatively newer residents of the cooler Canadian north than Caribou, with Caribou arriving on the scene about 1.6 million years ago (closer to the beginning of the last ice age), and Moose about 15 thousand years ago (closer to the end of the last ice age; see Hundertmark and others, 2002, and Weckwork and others, 2012, for further reading). But just how much energy-savings do these advantages lead to for our Caribou? Surprisingly quite a bit! In fact, our calculations suggest that the imaged Caribou seems little influenced by -34°C temperatures, with expenditure toward warming reaching only one half of a cheeseburger across 4 hours of exposure. The most impressive part about this figure is that, if we extrapolate from studies of calves or adults of a closely related subspecies,  metabolic heat production in Caribou is actually lower in the winter than it is in the summer (see McEwen and Whitehead, 1970, and Nilssen and others, 1984). If you’re wondering how such low expenditure on warming could be achieved in this species, stick around for our final discussion post. There, I’ll do my best to answer how and why we see such variations in thermoregulatory expenditure across species.
And what about our Arctic Fox? Interestingly, estimating thermoregulatory expenditure in this species isn’t easy – particularly when compared with our Caribou and Muskox. As we can see from our thermographic image above, the majority of heat lost to the environment in this individual occurs at the legs. In the field of thermal biology, such sites of exacerbated heat-loss are often referred to as “thermal windows”. To help “close” these thermal windows and reduce their loss of energy in cold environments, Arctic Foxes commonly enwrap their legs with their large and well-insulated tail.
During our cold-snap, using this type of enwrapment could result in a nearly 7-fold reduction in heat-loss across a four hour period. This means that the duration of time in which our Fox remained huddled will have a substantial influence on true expenditure toward warming. Sadly, without some chilly and prolonged observations, time spent huddling isn’t easy to estimate. But, to ensure that we’re drawing a somewhat realistic estimate of prolonged heat-loss in our Fox, I’ve assumed that half of its time was spent standing, and half of its time was spent huddling. Bearing that in mind, expenditure on warming in this individual amounts to… Only one human-sized bite (or one twentieth) of a cheeseburger across our 4 hour period! If we ignore tail-wrapping behaviour, we’re looking at approximately one third of a cheeseburger. A useful tail huh?

Bison and Mule Deer: Non-specialists?

Finally, to help us contextualize thermoregulatory expenditure in our specialists, I think it will be useful to compare their performance during our cold snap against some local “non-specialists”. (Note that I quote non-specialists here because when compared to an Ocelot or Marsh Widowbird, the below species are truly quite efficient. Nevertheless, the Yukon largely represents the northern end of each species’ range). Below are two infra-red thermographic images of a few conspicuous species meeting this criteria: the Wood Bison (left) and Mule Deer (right).

The Bison species complex is certainly not naive to colder climates. Rather, current genetic studies suggest that they’ve likely been hanging around northern North America for about 150 thousand years (see Froese and others, 2017). The curious problem with this species complex, however, is that the most northerly-living, and probably the most cold-adapted species grouping (the Wood Bison), suffered considerably declines from over-hunting in the past 5 centuries. By the late 1800s, population size estimates of the Wood Bison fell dangerously to approximately 300 remaining individuals. To help revitalize the population of Wood Bison, several individuals from the more southerly-dwelling species grouping (the “Plains Bison”) were moved north to the Wood Bison range, therefore increasing genetic diversity and the size of the breeding population. Thankfully, this revitalization effort was a spectacular success. A consequence of this effort, however, may have been the loss or dilution of certain cold-adapted traits. So, despite many years in North America, we might expect that efficiency of warming in the Wood Bison probably falls slightly short of other large and sympatric mammals. As for the Mule Deer, we can certainly expect that efficiency of warming falls short of other large mammals. Unlike the Caribou, Moose, and even Bison, this species is actually more adapted to warmer climates, and likely arrived in the Yukon as recently as 50 years ago owing to a warming climate (see Boonstra and others, 2018).
For the Wood Bison, our estimates suggest that expenditure on warming likely sits around two and a half cheeseburgers in our four hour period. And the Mule Deer? Approximately one and a half cheeseburgers! Confusing? See below.
Now, for the sake of time, let’s cut to the chase. Where does the cost of warming in our cold-snap sit for our non-specialists compared to our specialists?

Comparing Specialists and Non-specialists

Overall, these values do seem to suggest higher expenditure in our non-specialists when compared with our specialists. If we wish to make meaningful conclusions from these values, however, we’ll need to make one important adjustment: scale our estimates of thermoregulatory expenditure against usual daily expenditure (as we discussed in our last last discussion). So far, we’ve quantified the absolute amount of energy each of our observed animals would need to spend to maintain a constant body temperature in the cold. But each of these animals will already be consuming vastly different quantities of stored energy. So by comparing these absolute values among animals, we’re effectively comparing bananas to shoes (or Whitehorse to Destruction Bay); they’re incomparable. To solve this problem, we’ll need to look at relative expenditure toward warming. To follow what I mean here, take a look at the diagram below.

Two bar graphs showing absolute and relative energy use of 6 species of Yukon wildlife.
In the upper plot, we can see our cheeseburger estimates depicted in plot form. From this plot, we might be led to believe that the Wood Bison wins our award of the least efficient thermoregulator of our observed animals. Congratulations Wood Bison! Additionally, this plot may also lead us to believe that expenditure toward thermoregulation in cold-snaps doesn’t vary that much across Yukon mammals. However, once we represent expenditure toward thermoregulation as a percent increase in usual energy expenditure (the lower plot above), a new and more accurate picture begins to emerge. Here, we can see that relative expenditure toward thermoregulation does vary quite significantly across Yukon animals. Furthermore, we can also see that our least efficient thermoregulator is truly the Mule Deer, not the Wood Bison. In fact, compensating for heat loss during our cold snap likely required our Wood Bison to increase it’s energy expenditure by only 24%, while a similar compensation in our Mule Deer likely required a 135% increase in energy expenditure. To be clear, that’s an over-doubling of energy expenditure in the Mule Deer during a cold snap! Notably, long-lasting cold spells of this intensity could lead to serious survival risks for this species.
But we’re missing something in our plots and discussion: where do we humans fit in?

But what about us humans?

From experience, we know that even in full winter clothing, -34°C can be very uncomfortable. And using our imagination, we can also assume that removing our winter gear in such cold weather is a dangerous endeavour. So what does this discomfort and danger mean for our energy expenditure?

To answer that question: enter Jake. In the left image above, we can see Jake kneeling beside a resident male Muskox while donning winter attire suitable for the cold-snap. Even in such winter attire, we can see that Jake is almost certainly losing more heat to the environment than the adjacent Muskox. In the right image, our Muskox has been replaced with a resident female Caribou and Jake has bravely shed his outer jacket. Need I comment on relative expenditure? But, beyond our Muskox and Caribou, how does he stack up against our other observed species?
Bar graph showing relative energy use of wildlife and humans in Yukon.
Thought the Mule Deer was inefficient? As I mentioned before, evolution can be a wonderful process. Clearly, generations of outdoor living can lead to some impressive capacities to tolerate extreme weather. In my next and last post, we’ll discuss just how such capacities are achieved, and what they mean for species persistence in a rapidly changing world. But for now, I’ll leave you with a few pieces of information to think about:

  1. Although eating plenty of cheeseburgers might improve one’s comfort at -34°C, doing so wont keep hypothermia at bay if one remains unclothed. Rather, the extent to which any animal can elevate it’s metabolic rate is limited, regardless of how much food they eat. In humans, that limit seems to fall fairly close to the increase we might have seen in Jake if he were able to maintain a constant body temperature without his jacket. However, that limit appears only to be reached in extreme and long-lasting sporting competitions, such as the Tour de France.
  2. Adaptations to persist in cold have undoubtedly been helpful for surviving winters in the Yukon, but there is a second side to this coin: a loss of tolerance to warm weather and a bigger battle to face when coping with climate change.

Our Muskox and Arctic Fox might have an interesting future ahead of them.

Joshua Robertson

Joshua Robertson

Behavioural and Physiological Ecologist

Joshua is a behavioural and physiological ecologist currently living on Cape Breton Island, Nova Scotia. During his PhD at Trent University, Joshua sought to understand how small birds can cope with the high costs of body temperature regulation when challenged with other environmental stressors (such as human and predator exposure). He is currently extending the research to better understand energy management strategies in warm-blood animals.

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The Dangerous and the Benign: distinguishing between big scary bugs

The Dangerous and the Benign: distinguishing between big scary bugs

The Dangerous and the Benign: distinguishing between big scary bugs

This article was made possible thanks to support from the Environmental Awareness Fund. Engage and educate yourself in this 10-part blog series, about Yukon Biodiversity.

Banner Photo:  Yellow-tailed Horntail.  Photo credit: iNaturalist griffontrail in Dawson YT.

12 minute read – 

I think we can all agree that the past year has been pretty rough with the fires and the pandemic and the political unrest. When you add the appearance of large and intimidating Asian giant hornets on our fair continent, it makes it feel like we’re living through some biblical plagues. For those of you who have not been hysterically following the news, the Asian giant hornet (aka “the murder hornet”) is a massive hornet that earned its ominous nickname from its fun habit of decapitating hundreds of bees at a time and then carrying off the bee babies (the babees) to feed its own young. Also they sometimes kill people. Yikes. In the spring of 2020, they added to the general calamity that was all of last year by popping up in Washington, DC where the U.S. residents were understandably upset to have this horrible serial killer hornet added to their ecosystem.

iNaturalist observation of an Asian giant hornet.  No iNaturalist observations are to date recorded in Canada.  Photo Credit (c) Wonwoong Kim, all rights reserved

Obviously, the North American invasion by Asian giant hornets wasn’t kept secret and word traveled all the way to our remote territory. It’s probably because of this news that when a large insect with a prominent “stinger” and suspiciously hornet-like colouring was spotted during the Yukon Wildlife Preserve Bioblitz, some people got very nervous! But fear not, fellow Yukoners! The Yukon is a deeply unappealing habitat for the coast-loving murder hornets. The insect that garnered so much attention at the Bioblitz due to its large, scary appearance and prominent butt-spike is only a threat to felled trees. This benign bug is a horntail also known as a “wood wasp” (of the family Siricidae) and it could not be less like the invasive death machine it was mistaken for.

On the Left:  Yellow-tailed Horntail.  Found in Yukon.  iNaturalist Photo Credit M_Mossop

On the Right:  Asian giant Hornet.  Not found in Yukon.  iNaturalist Photo Credit (c) Alpsdake, some rights reserved (CC BY-SA)

Before we examine these insects in detail, a quick addendum. While scientists and academic types should never let personal bias cloud their research, I am not a scientist nor particularly academic so prepare for some bias. I HATE insects of the wasp/hornet variety. I mean the kind of loathing that would start a centuries long blood feud between families in olden times. Yes, they get props for being pollinators in their spare time but oooooh my god. These stripey menaces ruin every summer outdoor dining experience by completely disregarding your personal space and then rendering your beverage undrinkable after they drown themselves in it. Also, if they sting me, I die and that dynamic would sour any relationship. With that out of the way, let’s meet these bugs!

The Asian giant hornet or Vespa mandarinia (which sounds like a particularly elegant moped) is aptly named as it is the world’s largest hornet! Worker hornets are 3.5 cm long while queens get up to 5 cm. Their wingspans range between 4-7 cm which is probably more bug than the average person wants to deal with. If their size isn’t a giveaway, their large orange heads and black eyes make them very recognizable.

iNaturalist observation Asian giant hornet.  Photo credit: (c) Kim, Hyun-tae, some rights reserved (CC BY)

Unlike a lot of other hornets and wasps, these big hornets only nest in the ground. They favour forested areas in coastal environments which is bad news for our west-coast brethren but good news for the Yukon which is notably low on hospitable coastal regions. During the one-year life cycle of a nest, worker hornets usually forage alone and mostly hunt for beetles. The dark and sinister nature of these hornets rears its head in the fall when the colony needs a lot of protein to raise the next generation of queens.

In order to bring in the protein required to beef up their queens, workers abandon solo-foraging missions and band together for group raids. These raids attack high-value targets like the hives of honeybees or even the hives of other hornets. When these raiding parties hit a hive, they decapitate all the adults like they’re doing a re-enactment of the French Revolution then cart off the brood for food. These murder hornets really live up to the moniker as they can kill off thousands of bees in a few hours. Bees are already on a dangerous decline and Asian giant hornets can absolutely devastate local bee populations. This makes their appearance in America and Canada especially concerning.

Although the sudden appearance of murder hornets would be very on-brand for 2020, Asian giant hornets have been in North America before. They were discovered in Nanaimo, BC in August 2019 when beekeepers found a destroyed nest with a whole heap of headless bees outside of it. Their appearance in Washington is just an extension of their coastal conquest. Fortunately, the number of murder hornets in North America is still pretty low. This is good news for humans as people deaths from Asian giant hornets are usually due to disturbing a nest and incurring many stings. Unless you have an allergy (like some people who wrote this article), you have high chances of surviving a murder hornet attack if you have less than fifty stings. Rest easy, I guess? That being said, the Washington State Department of Agriculture had to order special suits to study Asian giant hornets because their massive stingers can pierce through normal beekeeping gear so maybe rest less easily.

It’s time to ease yourself into the warm waters of relief because the horntails that hang out in the Yukon are nothing like this. They’re not invasive, they don’t sting, and unless you’re a dead tree, they pose absolutely zero risk to your health and wellbeing. Yes, wood wasps are also intimidatingly large and similar in size to Asian giant hornets. They range in size between 1-4 cm with females tending to be larger than their male counterparts. Horntails get their name from their cornus: a stinger-shaped plate on the back of their body. Horn. Tail. Geddit? Even though it looks like a stinger, rest assured that it isn’t. Horntails don’t sting or produce venom and don’t really have any defenses other than looking scary. Females in particular look like they have a MASSIVE stinger but it’s actually an ovipositor that helps them lay their eggs into the wood of conifer trees.

iNaturalist image Yellow-tailed Horntail.  Whitehorse YT  Photo credit:  Jake Paleczny

Here’s a fun fact: female horntails have a symbiotic relationship with a fungus! Similar to horntails, basidiomycete wood decay fungi enjoys a nice rotting log. Female horntails help this fungus spread to new locations by carrying bits of it in a specialized pouch on their abdomen. When the female lays her eggs, she also deposits the fungus inside the rotting wood. The horntail also benefits from this arrangement as the larvae get to snack on the fungus after they hatch.

Unlike the newly arrived murder hornet, we’ve probably had horntails in the Yukon as long as we’ve had conifer trees. The reason you might not run into them all the time is that they spend most of their lives inside a tree. After a female lays her hundreds and hundreds of eggs in the wood of a felled or rotting tree, the young hang out in that log for 1-3 years. After they emerge from their timber home as a fully grown adult, they only live for 3-4 weeks! Because they spend so much time in wood, young adults sometimes show up inside people’s homes because the lumber they’ve been tunneling around in has been used as construction material. So they’re not out there murdering bees and giving horrible stings but they can occasionally give you a nasty surprise by exploding out of your new rocking chair.

iNaturalist Yukon.  Yellow-tailed Horntail.  Photo Credit:  Bruce Bennett

I hope your fears are assuaged and you won’t dread painful stings and bee death when you encounter a big scary bug in the Yukon wilds. The horntail might be intimidating in appearance, but it’s a passive insect that just wants to spend most of its life noodling around in a tree. Asian giant hornets are definitely horrible nightmare insects that were probably manifested into existence as punishment for our sins but at least they’re horrible nightmare insects that don’t live up here.

iNaturalist Asian giant hornet resting on human hand.  Photo credit:  (c) elfsama, some rights reserved (CC BY-NC)

Joelle Ingram

Joelle Ingram

Human of Many Talents

Joelle is a former archaeologist, former wildlife interpreter, and a full-time random fact enthusiast. She received her master’s degree in anthropology from McMaster University. One of the four people who read her thesis gave it the glowing review “It’s a paper that would appeal to very specific group of people,” which is probably why only four people have read it. Her favourite land mammal is a muskox, her favourite aquatic mammal is a narwhal. She thinks it’s important that you know that.


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Bear Poo and You: learning about Yukon Bears with the OURS research project

Bear Poo and You: learning about Yukon Bears with the OURS research project

Bear Poo and You: learning about Yukon Bears with the OURS research project

This article was made possible thanks to support from the Environmental Awareness Fund. Engage and educate yourself in this 10-part blog series, about Yukon Biodiversity.
Banner Photo:  Grizzly bear scat.  iNaturalist OURS page Photo Credit Lucile Fressigné
15 minute read –
If you, like me, grew up in the Yukon, bear awareness training has been part of your life since you were a wee child. Some combination of videos and booklets have let you know that yes, bears sure are out there and this is what you should do in response to a variety of bear encounters. But here’s the thing, just how aware of bears are you really? The Yukon is renowned for its bears but there are actually some gaps in our bear knowledge, particularly when it comes to just how many bears are actually out there! Population size is important for studying everything from the spatial distribution to the health of a species, but there hasn’t been a bear survey in the Yukon since the 1980s. Unless the Yukon bears are both immortal and not having babies, that information is a touch outdated.

Lucile Fressigné is leading an on-going study that seeks to fill in this gap in bear population knowledge. Starting in 2020, she started a community-based project to survey the Yukon’s bear populations in a creative way that also doesn’t bother the local bears: by collecting their scat! That’s right, Operation Ursus Research using Scat (OURS) is aimed at updating and providing a scientifically reliable estimate of the population size of Yukon bear species using a non-invasive DNA-based method that relies on scat samples. Last year, the study focused on collecting samples in the Mount Lorne, Marsh Lake, Tagish, and Fish Lake areas of the territory. Fressigné offers Yukon residents the opportunity to be part of this project and help build this sample collection by offering free collection kits that can be dropped off at community centres in the study areas. Yes, you too can take part in bear science!

OURS aims to get an estimate on both grizzly (Ursus arctos) and black bear (Ursus americanus) populations. These bears tend to be especially difficult to inventory and monitor as a low number of bears will occur over a large home range and they tend to be avoidant by nature. Grizzlies are the largest of the two and are very distinctive with their dished face profile and defined shoulder hump. They are often referred to as “brown bears” but their colours can range from white to almost black. They most commonly have “grizzled fur”: a deep brown with lighter ends. Apparently, no one told them that frosted tips went out of style in the early 2000s.

Grizzly Bear iNaturalist Photo Credit L to R:  Cameron Eckert, Bdobrowo, and OURS Facebook page.

In 2018, grizzlies in western Canada were designated as a species of special concern. This means that they are a species that does not meet the criteria of an endangered or threatened species but is particularly vulnerable, and could easily become endangered, threatened, or extirpated. This rapid loss of population could happen from a variety of factors such as restricted distribution, low or declining numbers, and/or specialized habitat needs or limits. One of the many benefits of having a population estimation for grizzly bears is that it can help provide a basis for a proactive conservation strategy.
Black bears, as the name would suggest, are most often black but can also be blonde, grey, cinnamon, and brown (in which case, the name is very misleading). They have a straight face profile and lack the shoulder hump present in grizzlies. They also lack the species of special concern status but this doesn’t necessarily mean there are more black bears in the Yukon because, like grizzlies, the last time there was a black bear population estimate was in the 90s. Without an updated population estimate, we really don’t know if we should be concerned about them as well.

Black Bear iNaturalist Photo Credit L to R: Cameron EckertYukonAnnie, John Meikle

At first blush, scat analysis might not seem like the most appealing method for studying bear populations but there are a lot of advantages to this method. First of all, it’s incredibly non-invasive when compared with methods like radio collaring. In order to get a collar on a bear, they have to be tranquilized which can result in the injury or even death of the bear (bummer!). The injection site can get infected, the radio collar can get snagged, and there’s a lag between when the dart hits the bear and when the tranquiliser takes effect. During this lag time, bears can run out into a body of water where they can’t be recovered because ursine lifeguards are not a thing.

Hair snags are another non-invasive method for population estimations. This is the most common method of population analysis and it’s done by placing a tantalizing lure near a string of barbed wire. When an animal comes for the lure, they leave a cheeky tuft of hair behind. However, scat analysis doesn’t need a lure/barbed wire setup, you can find it everywhere bears dwell, and it is very easy to identify whereas hair tufts can be tricky to spot. Odds are, if you spend some time in the woods, you’ve come across them before. And believe it or not, there is a ton of information to be gained from analysing bear body waste!

Bear Scat.  iNaturalist Photo Credit L to R:  Grizzlyann, Gerald Haase, Lucile-OURS.

Because scat is found wherever the bear decided to leave it behind, it tells you where and generally when the bear has been so it’s very useful for identifying bear habitats. The DNA analysis technique used on these scat samples is called Genotyping in Thousands by Sequencing (GT-seq). This method can extract information regarding the species, sex, and individual identity of the bear. Knowing this poop-extracted bear information can help scientists track the movement and migration of individual bears as well as trends in bear parentage! Scat also contains cortisol (the stress hormone) which can be used to monitor the relative stress levels of the local bear populations. This can be really important for bear conservation because it can tell us whether bears in certain areas are experiencing more stress than others (are bears living by highways more stressed than those that don’t, for example).

We are generally aware of what bears are eating but scat analysis can give us specific statistics regarding how often and how much bears are consuming of different foods. It also helps chart changes in diet. If one food is present one year and absent the next, this might indicate environmental changes that made this food source inaccessible. OURS can also see how bears are affecting their food sources in turn. As part of this project, Fressigné is partnered with the Kwanlin Dün First Nation who are interested in how or if bear predation is affecting the declining moose population in the Fish Lake area.

The goal of the first season of research was to test the community-based sampling method and generally gauge the public’s interest in the project. It was an opportunity to implement new genetic technology on the collected samples and to test whether the scat collection methodology would yield enough useable DNA. It also aimed to identify the presence and distribution of bears in the sampling areas. Moving into the second season of sampling, OURS is going to adopt a more rigorous sampling method by hiring students to run survey transects in the study area and by partnering with more First Nations and groups that are involved in traveling and exploring through the Yukon wilderness. This includes hunters and trappers, tourism companies, mining companies, summer camps, schools, and very lost tourists. Just kidding on the last one, being a tourist is both dangerous and illegal at the moment.

The OURS project is primarily about providing a population estimate but it’s more than just a bear abacus. Studying the genetic markers in bear scat reveals information about the genetic diversity in bear populations. This work also helps emphasise how important it is to maintain this diversity in order to keep these vulnerable apex species healthy and stable. The groovy analysis from these scat samples will also provide tons of info about bear stress levels, parentage, and the trends and impacts of bear predation. Who knew poo could be so educational?

Bear Scat.  iNaturalist Photo Credit: 1st Alisonp, 2nd and 3rd Grizzlyann

The project is important for future bear conservation efforts and not just because it gives us an approximate bear count. This study can be used to monitor the impact of climate change on bear behavior and population trends. Continued bear scat surveys can also reveal critical/preferential habitats for bears, and lead to the restoration of these habitats or the creation of protected areas that would minimize human/bear conflicts. Which is great because I don’t know about you, but I don’t want to fight a bear. But in all seriousness, these types of conflicts tend to end badly for the bears so it’s best if they can be mitigated or avoided entirely.

As you can see, there are a lot of benefits to the non-invasive, cost effective, kind of smelly, and highly informative research method of scat sampling. This method will hopefully allow the OURS project to collate an estimate of our Yukon bear populations and improve the scope of our bear-related knowledge. If you want to learn more about the project, check out the OURS Facebook and iNaturalist page and consider, come this spring, being part of the bear bowel movement collection crew!

OURS Facebook:
OURS iNaturalist:

Joelle Ingram

Joelle Ingram

Human of Many Talents

Joelle is a former archaeologist, former wildlife interpreter, and a full-time random fact enthusiast. She received her master’s degree in anthropology from McMaster University. One of the four people who read her thesis gave it the glowing review “It’s a paper that would appeal to very specific group of people,” which is probably why only four people have read it. Her favourite land mammal is a muskox, her favourite aquatic mammal is a narwhal. She thinks it’s important that you know that.


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Rusty Blackbird: the mysterious decline of a common boreal bird

Rusty Blackbird: the mysterious decline of a common boreal bird

Rusty Blackbird: the mysterious decline of a common boreal bird

This article was made possible thanks to support from the Environmental Awareness Fund. Engage and educate yourself in this 10-part blog series, about Yukon Biodiversity.
Pam Sinclair’s contribution was supported by the Canadian Wildlife Service of Environment and Climate Change Canada

15 minute Read – 

One cold grey day in late October, we went looking for American Dippers in a salmon spawning stream in southwestern Yukon. It’s always fascinating to see those strange little songbirds walk right in to the surging water and disappear as they search for food in the rocky stream bed, and then pop back out on shore. Arriving at the creek, we saw a couple of birds right away on a tiny rocky island in the rushing water. But peering through fogging binoculars in the dim grey light, it took a moment for the image to take shape and for us to realize that these were not dippers, but Rusty Blackbirds! Rusty Blackbirds nest in forest wetlands throughout the Yukon but most are well on their way to wintering grounds in the Mississippi River area by late October, and it’s unusual at any time to see them in fast-moving water.

American Dipper Klukshu YT taken March 2018

Sure enough, there were also two dippers working their way along the stream, and it was striking how similar the two species looked and behaved. The blackbirds were plunging only their heads into the water, while the dippers didn’t hesitate to go under entirely; but both appeared to be feasting on salmon eggs. This was typical for dippers but I’d never heard of blackbirds taking advantage of this food source. Being opportunistic is not unknown for Rusty Blackbirds; in winter, they eat pecans but can’t crush the shells on their own. Instead, they either pick up the pecan pieces that larger grackles have dropped or hang around areas where roads or driveways are close enough to pecan trees for vehicles to have crushed some fallen nuts!  They’re also known to gather in large numbers to eat compost and can even been found snacking on the garbage piles at the Whitehorse landfill. It made me wonder: if Rusty Blackbirds can be so opportunistic, why has their population declined so dramatically?

Rusty Blackbird and American Dipper Southern Yukon taken Oct 2020.

A quick overview of what we do know: “Rusty Blackbird” is a title very well suited to these birds. Male Rusty Blackbirds are completely black during the spring breeding season but during the winter, they have “rust” colored plumage blending into the black. The females also have rust-coloured edges on their grey-brown plumage, hence the name! These are migratory birds that are only found in North America. As stated in Audubon website: “Birders might say that this blackbird is rusty because it spends so much time in the water.” And that is due to the fact these birds prefer a damp environment.  These boreal forest residents enjoy forest wetlands including slow moving streams, swamps, marshes, beaver ponds, and the edges of pastures. In the Yukon, you can look for them in these forest wetlands in spring and early summer, and along the edges of rivers and lakes in the fall.

Male Rusty Blackbird first year taken Whitehorse YT Sept 2020.

Until recently, the Rusty Blackbird was simply part of the fabric of the boreal forest landscape, common across the region from Alaska to Labrador. Few bird surveys or studies were conducted within its inaccessible, buggy breeding range. Blackbirds in general have long been considered agricultural pests because they eat grain and corn, and for this reason, when Canada and the U.S. signed a treaty to protect migratory birds more than a century ago, blackbirds were left out of the agreement. Nobody paid much attention to the Rusty Blackbird. Then in 1999, well-known U.S. bird biologists Russ Greenberg and Sam Droege noticed that these birds were disappearing from southern U.S. wintering grounds, and published a paper showing that numbers of Rusty Blackbirds had been declining for decades. The Rusty Blackbird soon gained the dubious distinction of having the steepest population decline of any North American songbird: 85 to 95% of the birds had disappeared in 40 years. Nobody knew why. Nobody knew much about this species at all.

Why was the Rusty Blackbird in trouble? It spends the summer in the vast and relatively undisturbed boreal region. In winter, it resides in “bottomland” habitats like oak forests with puddles and ponds in the southeastern United States. There has been a lot of deforestation in that area, which often leads to complication and declines in animal populations, and probably contributed to the historical decline of Rusty Blackbird. But the slower recent pace of deforestation is not enough to explain the decline in Rusty Blackbird numbers in the last few decades. Bird biologists and conservationists were concerned. If this common boreal bird is declining, something must be seriously amiss in its environment. But what? In order to figure out what was going on, and ultimately to figure out how to stop the decline of this bird, biologists and conservationists from the U.S. and Canada formed the International Rusty Blackbird Working Group and made a research plan.

Over the last two decades, there have been incredible advances in the technologies used to track the movement of birds. This has helped both the small group of scientists studying the decline of Rusty Blackbirds and the study of migratory birds as a whole! In the case of Rusty Blackbirds, we have learned that their annual cycle is more complex than simply migrating back and forth between nesting and wintering grounds. For example, a young Rusty Blackbird which hatches in the Whitehorse area in June, will have left the nest and grown its full set of feathers by July. But unlike many local songbirds that start heading south in early August, the young Rusty Blackbird will then start growing a whole new set of feathers, and settle in to a good feeding area for a month or two, before heading south by late September or early October. From there it will leave to spend around a month in the Canadian Prairies or the Dakotas. From there, it’s on to wintering grounds in the Mississippi valley, heading north in spring but stopping for a month or so in March/April at another good feeding area before returning to the nesting grounds.

Adult male Rusty Blackbird WhitehorseYT Sept 2020.

Instead of following the nesting-migrating-wintering-migrating pattern that many migratory birds follow, the Rusty Blackbird’s year involves major stopovers at two or three additional locations. Does this make it more vulnerable, because it relies on good, safe food sources at about five major locations each year? Or does it make it more adaptable, because if one location does not meet its needs, it can move on to the next?

Typically for any ecological question, the answers are more complicated than expected. When the Rusty Blackbird working group set out to determine what was causing the decline, several possibilities were explored. Rusty Blackbirds are susceptible to high levels of mercury toxicity, especially in eastern North America where pollutants from coal-fired electrical generating stations cause acid deposition in wetlands, which releases naturally-occurring mercury. Rusty Blackbirds are high in the food chain because they consume aquatic insects like dragonfly larvae, which eat smaller invertebrates. This causes bioaccumulation resulting in high levels of mercury in these birds. Bioaccumulation is the accumulation over time of a substance and especially a contaminant (such as a pesticide or heavy metal) in a living organism from all sources including water, air, and diet. Animals higher in the food chain, such as the Rusty Blackbird, can acquire a larger load of contaminants as they will consume other creatures that have also consumed contaminants.

Rusty Blackbird Southern Yukon taken Oct 2020.

But Rusty Blackbirds are also declining in areas with little acid deposition. On the wintering grounds, other blackbird species (Red-winged Blackbirds and Common Grackles, along with starlings and cowbirds) have been legally killed by spraying the birds as they roost in flocks at night, or by putting out poisoned bait to prevent them from feeding on agricultural crops. Rusty Blackbirds sometimes share roost sites with these species and may be inadvertently killed as well. There is little information on the species composition of affected flocks, so it is unknown if this is a major factor in the decline of Rusty Blackbirds. Habitat loss in the boreal region is occurring, from conversion to agriculture, oil sands development, flooding for hydro dams, and forest harvest. This is not occurring at a pace that would fully account for the decline but it is likely a contributing factor. Pesticide runoff, and habitat loss due to agricultural intensification and urbanization, may be affecting Rusty Blackbirds on their stopover sites on the Great Plains. In short, no single factor explains the decline. Possibly, all of these factors are contributing.

Rusty Blackbirds are found throughout the Yukon, and biologists at the Canadian Wildlife Service (CWS) in Whitehorse were keen to help investigate this declining local species. When research began, some very basic knowledge of the species was lacking, such as how to distinguish first-year birds from adults based on their plumage. This is straightforward for most songbirds, but it turned out to be difficult in this species. When investigating rates of reproduction and survival in order to determine the causes of decline, it is crucial to know the ages of the birds, because survival is usually much lower for inexperienced first-year birds. It was also discovered that Rusty Blackbirds are “neophobic”, or fearful of new things in their environment, compared to other blackbirds such as Red-winged Blackbird. This makes it difficult to capture Rusty Blackbirds for study.

Rusty Blackbird male Whitehorse YT taken June 2019

After trying several techniques, mist nets being particularly successful, CWS biologists were able to capture good numbers of Rusty Blackbirds in Whitehorse. These successful captures provided a unique opportunity to figure out how to distinguish first-year from older birds. In September, when Rusty Blackbirds are common around Whitehorse, birds in the hand can be aged with certainty by examining the growing area of ossification (hardening) of their skull, which appears as white dots which can be viewed through the bird’s thin translucent skin by a skilled observer, with no harm to the bird. Once the birds arrive at the southern bird banding stations in the Canadian prairies and the U.S., the young birds’ skulls have ossified and are identical to those of adults. Taking advantage of this unique opportunity, we were able to compare first-year birds with older birds and determine the subtle differences in colouration. Both male and female Rusty Blackbirds have white around their eyes in their first year of life that isn’t present in adult birds. The amount of this white “eye-liner” varies from bird to bird but if it’s present, it’s a first-year bird. The results were provided to researchers further south, so that they could reliably determine the age of each bird in their studies. While conducting this work in Whitehorse, we were also able to confirm that Rusty Blackbirds grow two complete sets of feathers in their first four months of life, which is unusual among bird species, and that they stay in the boreal region for many weeks in order to grow all of those feathers before heading south.

It can take a lot of effort to chart the life and migratory cycles of even a single bird species. Even after we gain a better understanding of the factors affecting their lives, discovering the cause or causes behind a population decline can be very difficult as is the case of the Rusty Blackbird. However, there are still some conservation actions that would very likely help the Rusty Blackbird, the natural environment in general, and human health: reduced use of harmful pesticides such as neonicotinoids, maintaining natural wetland habitats within intensive farmland, and reducing the use of coal to generate electricity. Migratory birds, even those that stay within North America, make us realize our interdependency with other nations and our shared environment.

For more information on the Rusty Blackbird, go to

Written by Pam Sinclair (Canadian Wildlife Service) in conjunction with Joelle Ingram.
Where not otherwise noted photo credit: Pam Sinclair


Edmonds, S. T., Evers, D. C. , Cristol, D. A., Mettke-Hofmann, C. , Powell, L. L., McGann, A. J., Armiger J. W., Lane, O. P., Tessler, D. F., Newell, P., Heyden, K. and O’Driscoll, N. J. (2010). Geographic and seasonal variation in mercury exposure of the declining Rusty Blackbird. Condor, 112(4): 789–799. 

Greenberg, R. and Droege, S. (1999). On the decline of the Rusty Blackbird and the use of ornithological literature to document long-term population trends. Conservation Biology, 13(3): 553–559. 

Greenberg, R., Demarest, D. W., Matsuoka, S. M., Mettke-Hofmann, C., Evers, D., Hamel, P. B., Luscier, J., Powell, L.L., Shaw, D., Avery, M. L., Hobson, K. A., Blancher, P. J. and Niven, D. K. (2011). Understanding Declines in Rusty Blackbirds. Studies in Avian Biology, 41: 107–126. 

Mettke-Hofmann, C., Sinclair, P. H., Hamel, P. B. and Greenberg, R. (2010). Implications of prebasic and a previously undescribed prealternate molt for aging Rusty Blackbirds. Condor, 112(4): 854–861. 

Recording of a presentation on Yukon Rusty Blackbird research:
Sinclair, P. 2020. Molt ecology of Rusty Blackbird in southern Yukon. International Rusty Blackbird Working Group Symposium, The Wildlife Society 27th Annual Conference, October 2020.

Joelle Ingram

Joelle Ingram

Human of Many Talents

Joelle is a former archaeologist, former wildlife interpreter, and a full-time random fact enthusiast. She received her master’s degree in anthropology from McMaster University. One of the four people who read her thesis gave it the glowing review “It’s a paper that would appeal to very specific group of people,” which is probably why only four people have read it. Her favourite land mammal is a muskox, her favourite aquatic mammal is a narwhal. She thinks it’s important that you know that.


Pam Sinclair

Pam Sinclair

Bird Conservation Biologist

Pam Sinclair is a Bird Conservation Biologist with the Canadian Wildlife Service of Environment and Climate Change Canada, in Whitehorse

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Winter Heat Losses

Winter Heat Losses

Winter Heat Losses

15 minute read –

This is Part 2 of a 4 part series by guest author and ecologist, Joshua Robertson on how wildlife at the Yukon Wildlife Presere stays warm (thermoregulates) in the winter. Read Part 1. The article was edited on March 15, 2021 to update heat loss calculations.

In my last post, we discussed the unfortunate reality that winter in the Yukon isn’t cheap. Each year, we spend our money on mittens, insulated boots, toques, and hand-warmers to protect ourselves from hypothermia or nasty frost-bite injuries. (Or we don’t, and pay with a mysterious and unpredictable loss of feeling in certain appendages. It’s not something I’d recommend).

But just how inefficient are we? And why?

For those living in Whitehorse or Dawson, heating a living space to a comfortable degree probably means spending at least $75.00 more on electricity bills each month relative to the summer or fall. Similarly, for those in rural areas, costs of warming a home are likely paid by increasing the total amount of wood burnt per day. And as we know, collecting and splitting that wood is not easy, nor is it quick.

But as the wildlife enthusiasts that we are, we also took a step back from our human experience to ask  “what do costs of winter look like for other year-round and sympatric animals?” (remember, sympatric means “living in the same place”). In doing so, we stumbled upon three rather intriguing trends:

  1. Like us, practically all animal species that one is likely to observe in a Yukon winter (each of which are “endotherms”, meaning that they produce their own body heat) are almost certainly paying extra to keep their bodies warm. Rather than paying in dollars, however, these animals are paying with proteins and fats that were sourced from breakfasts of mice or spruce cones.
  2. For some species, such as the Red Fox, the costs of keeping warm in temperatures below -20°C amount to chump-change. One Masked Shrew extra a day or so. No big deal. For other species, such as the Black-capped Chickadee, such costs can be frightening astronomical (+70% of usual expenditure). Although these differences in the relative costs of warming across animals can be partly explained by variations in body size, variations in the capacity to capture and store body heat also seem to play an important role in the story.
  3. Despite inhabiting cold environments for thousands of years, and despite using high-tech, insulative winter gear, humans appear to spend quite a bit more energy on keeping warm throughout the winter than one might expect – particularly when compared with other large mammal species. But just how inefficient are we? And why?

Now that we’ve summarized our previous findings, let’s return to the objectives that we outlined in our last post. Jake Paleczny and I were interested in understanding just how efficient or inefficient we humans are at keeping warm when compared with a few animal species that reside in the Yukon through the winter months. We were also curious to know how the efficiency of keeping warm varied across a suite of animal species, and why such differences occur. To gather more information, we used an infrared thermographic camera and some biophysical knowledge to measure the amount of heat that animals at the Yukon Wildlife Preserve (including Jake) lose to the environment on a cold day. With these measurements, we then estimated and compared just how much energy each animal would have to spend to maintain a stable body temperature throughout a few hours of cold exposure. Now that we’re back up to speed, here’s were left off:

Thermal image of Jake's face.

Above is an infrared thermographic image of Jake, wandering the preserve at around -12°C. Remember, in these types of images, bright colours represent warm surfaces and dark colours represent cold surfaces. From this image, we calculated that if Jake were to continue wandering the preserve for 4 hours, the amount of heat lost across his face alone would amount to one tenth of a MacDonald’s cheeseburger. To this, you said “that’s not so inefficient!” (or at least you may have in my internal dialogue). And my reply?

Well, why don’t we step back and have a look at Jake’s entire body. But before doing so, let me note that Jake is no novice when it comes to outdoor exploration in cold weather. He’s spent enough hours in sub-zero temperatures to know that wearing Converse shoes and forgoing underlayers simply isn’t worth the discomfort (as much as the teenage version of myself denied it).

Thermal image of Jake walking at the YWP.

Okay, I’ll admit that I’m not the greatest field photographer. Nevertheless, the thermographic image above will suffice to make a reasonable estimate of heat-loss across Jake’s entire body on this chilly day. An important observation from this image is that parts of Jake’s body are slightly warmer and poorer insulated than others; his head, hands, and upper back seem to be particularly susceptible to heat-loss. This tells us that if we want to paint a reliable picture of Jake’s whole-body heat-loss, we must first estimate the rates of heat-loss across major body parts (the torso, pelvis, legs, arms, head, and hands), then sum these values. Below, this is precisely what I’ve done. I’ve also expanded our whole-body estimate across 4 hours of outdoor walking to be consistent with when we estimated heat-loss across Jake’s face alone. So how many cheeseburgers worth of energy is Jake using to keep warm at -12°C? 

Two and one tenths cheeseburgers! That’s quite a lot of cheeseburgers!

If you’re a lover of winter like myself, you’re likely thinking “wait a minute. I spend plenty of time outside in cold weather and I can’t possibly be losing that much energy when I do. How does this make sense?” This is an insightful concern to raise. So, on reflection, is our estimate missing an important piece of information? The answer is, yes, it is; and that is, just how much heat do we generate and lose, on average, barring exposure to the cold? What we are really interested in is not how much energy Jake is losing as a consequence of heat-loss, but rather, how much more (emphasise more) energy Jake is losing relative to his normal day-to-day life by being out in the cold. Jake is already spending a certain number of cheeseburgers on heat production by virtue of being a “warm-blooded” animal (or “endotherm”). But how many more cheeseburgers is he using for heat production at -12°C? We can call this unknown value his costs of “cold-induced thermogenesis”, a fancy way of saying “his costs of making new heat (called thermogenesis) to make up for what is lost to the cold air”. To clarify what I mean, take a look at the diagram below.

Chart showing thermogenesis (heat transfer).

As I mentioned above, Jake is always going to be spending some amount of energy on heat production, regardless of the weather. Such heat production is an intrinsic property of life as an endotherm and we can define to its absolute minimum value as “basal heat production”. (In reality, I’m over-simplifying here. Even “cold-blooded animals”, or ecotherms, produce some heat just from existing, but basal heat production in these animals is small enough to ignore). In the diagram above, basal heat production is indicated by the arrow leaving “basal metabolism” (meaning, “minimum bodily function”) and pointing to “heat production”. So, this means that if we’re truly interested in how much more energy Jake is losing from cold-exposure relative to normal circumstances (again, his costs of “cold-induced thermogenesis”), we should take his measured heat loss and subtract his basal heat production. But doing so only gets us part of the way there. Why? Because we’re also missing a few other important and regular contributors to heat production that we’ll need to subtract. These contributors are digestion and physical activity, each of which are also indicated with arrows in the above diagram and were briefly touched on in our previous discussion. 

Conveniently, in Jake’s case, already know his activity level; he was walking at a leisurely pace. Estimating Jake’s digestion level, however, is slightly trickier. For the sake of simplicity, we’ll just assume that he skipped his lunch. And lastly, what about his basal heat production? Thankfully, plenty of research has been done on basal heat production in humans, so we don’t need to make an estimate from base principles. For this post, I’ve used Ken Parson’s book called “Human Thermal Environments” as a resource. With all of this information in place, we’re set to estimate Jake’s true costs of cold-induced thermogenesis. And the result is…

Approximately one whole cheeseburger! That’s right, despite donning full winter gear, Jake would still use a full cheeseburger worth of energy to keep warm on his four hour walk. Recall, that’s one more cheeseburger worth of energy than he’d normally use in day-to-day life. Now

  1. If you’re spending long periods of time outdoors in the winter, you have very good reason to eat second helpings; and,
  2. For ease, these estimates are made assuming no wind. Factor in a modest wind and we’re looking at around pi (3.14…) cheeseburgers.

I know, I know, I’m being long-winded. Enough about Jake and pi. What about the other animals at the Yukon Wildlife Preserve? How do they match up? Well, remember the Thinhorn Sheep (or Dall Sheep)? If not, have a look at the thermographic images below.

With a quick look at the images, we can already see that the amount of heat escaping from most of the sheep’s body is less than that escaping from Jake’s. But does this truly mean that the sheep is spending less energy on warming in the cold than Jake is? Well, using the same approach we used to estimate Jake’s cost of heat loss (see above), the answer is…

No! Well, more accurately, a tepid not quite. According to estimates of basal heat production in a close relative, the Bighorn Sheep, this Thinhorn Sheep is probably using about one and three quarter cheeseburgers worth of energy to maintain a stable body temperature in -12°C (and again, across 4 hours). That’s quite close to Jake’s value of one cheeseburger. But, given that this handsome fellow is wearing nothing but his fur, and given that he’s probably slightly heavier than Jake, you have to admit, that’s impressive. I should also mention that my estimates of heat loss for the Thinhorn Sheep are coarse and likely higher than true values, thanks to the limited amount of data available on body size in this species. My guess is that the true number of cheeseburgers used to counteract the cold exposure is sitting slightly below one.

Okay, so the Thinhorn Sheep can contend with Jake in winter gear, but can’t totally outstrip him. What about a different species that is commonly viewed in the Yukon? Perhaps one with a slightly larger body size? A good candidate here might by the North American Moose (depicted in the thermographic images below).

Thermal image of MooseThermal image of Moose

These images are curious. For those who have had the fortunate opportunity to view Moose at close proximity, the rapid rate at which heat is escaping from the legs and body of this individual may not be too surprising. Indeed, the thickness or “depth” of the fur in this species is not large, meaning that it  probably doesn’t serve as a magnificent insulator. The curious side of this information, though, comes from the knowledge that Moose have survived winters in northern North America for thousands of years. For that reason, one might expect their natural insulation to be slightly more effective, correct? This conundrum is one that I’ll dissect in a later discussion, but for now, let’s get to the important question. How costly is our perceived heat loss for the Moose in question?

If you guessed “very”, your both correct and incorrect. On our -12°C day, this Moose is likely losing about 10 cheeseburgers worth of energy to heat across a 4 hour period. That’s quite a lot of cheeseburgers. However, the average rate at which Moose produce heat is remarkably high, owing to a fairly fast metabolic rate. If we factor in this rapid metabolic rate (as we have for Jake and the Thinhorn Sheep) our Moose is actually spending less on warming, relative to it’s usual energy consumption, than Jake is – only three-quarters of a cheeseburger Impressive huh?

So it seems that Jake is having a tough time standing up to the Yukon competition. But just for fun (and a hint of cruelty), why don’t we test him against a true specialist; a species that is unique adapted to harsh and extreme winter conditions.

Now there is a good contender. Above, we have two thermographic images of the same female Muskox. Take a close look at the back and flanks of our Muskox in the right-hand thermographic image. It’s difficult to tell by eye, but by using a computer, I can tell you that the average temperature on the surface of this body region is around -7.8°C. For reference, the core body temperature of a Muskox hovers around 38°C (you can see this in a study by Schmidt and others that was published last year in the journal Scientific Reports). This means that barely any of the heat produced by the body of this muskox is escaping to the external environment. As for Jake, the average temperature on the surface of his back was around -0.4°C – a whopping 7.4°C higher. Thought the insulation on the Thinhorn Sheep was impressive?

“But what about total heat loss in the Muskox?” you ask? Before I reveal the answer, I’ll note that early research in this species has shown that basal energy expenditure in adult females approximately triples that of an average adult human. Not as high as the Moose, but notably high nonetheless. Remember, from the diagram above, this means that metabolic heat production during day-to-day life will be raised in our Muskox relative to Jake. Nevertheless, the total cost of heat loss in the imaged individual is a surprising..

– One half of a cheeseburger! Yes, that’s negative one half of a cheeseburger. And this value isn’t even proportional to usual energy consumption in the Muskox. This means that at -12°C , our Muskox doesn’t appear to be spending energy on extra heat production at all. Rather, she’s actually accumulating heat. Despite knowing that this species is strongly adapted to cold climates, I have to admit, this estimate still surprised me. Insulation capacity of the Muskox is truly astounding and can partly be attributed to their interestingly soft and woolly underlayer called “qiviut”. As you can imagine, maintaining this level of insulation in the hot days of the summer could contribute to extreme heat stress. To avoid this issue, Muskox shed their qiviut each summer, thus allowing them to more easily dissipate their excess, and potentially toxic, body heat.

Muskox shedding Qiviut.

You might be thinking that all of this information is certainly interesting, but a bit restricted. After all, just how extreme is -12°C anyway? And what if Jake weren’t wearing any insulative clothing? How would he compare to other Yukon endotherms then? These are all great questions. In the next post, I’ll use thermographic images captured during a cold snap in January to answer each of them to the best of my abilities. After that, we’ll see if we can start drawing some meaningful inferences from how the heat-storage efficiency of these animals compare with one another. For now, I’ll leave you with the below, rather startling image.

Thermal image of Jake and Caribou at -35c

To re-assure you – yes, you’re reading the scale bar correctly.

Joshua Robertson

Joshua Robertson

Behavioural and Physiological Ecologist

Joshua is a behavioural and physiological ecologist currently living on Cape Breton Island, Nova Scotia. During his PhD at Trent University, Joshua sought to understand how small birds can cope with the high costs of body temperature regulation when challenged with other environmental stressors (such as human and predator exposure). He is currently extending the research to better understand energy management strategies in warm-blood animals.

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Staying Warm in Yukon

Staying Warm in Yukon

Staying Warm in Yukon

10 minute read – 

This is Part 1 of a 4 part series by guest author and ecologist, Joshua Robertson on how wildlife at the Yukon Wildlife Presere stays warm (thermoregulates) in the winter.

In the south of the Yukon, winter has long since settled in. Snow has accumulated, ice has formed, and daytime temperatures have regularly fallen below 0°C for many weeks. At most homes, winter coats have found their seasonal places at front doors, and skis and snowshoes now clutter entrance-ways and garages. Winter can be an exciting time of year for outdoor enthusiasts, fireside readers, and West Dawsonites alike (who can set aside their reliance on the George Black ferry for trips to town), and now is a great time to savour it.

Yet, hiding behind this winter enjoyment lies a sneaky and particularly interesting financial change; energy bills (or wood consumption, for those living off-grid) are steadily elevated. Yes, according to estimates made by Yukon Energy, monthly energy costs for the average home have risen by at least $75.00 since September. It may be several hundred dollars more if you use electric heat. Otherwise odds are good that your home heating bill has gone up significantly. These costs are certainly not small and emphasise a long-known and unfortunate reality for northerners; winter can be expensive. But, if you happened to complain about your rising energy costs to a local biologist, you might hear them say that you, human, should not feel so alone; it all depends on how you think about the word “energy”.

Energy is, at its simplest, the capacity to do work.

Throughout the duration of my PhD, I’ve found myself in many conversations about this ever-present and ever-charged word “energy”. To engineers, the term can stir thoughts of turbine velocities and kilowatt hours. To biologists, the topic most often brings up conversations about “ATP” (or, “adenosine triphosphate”), a molecule that is known to power most processes within a living cell. On the surface, both perspectives of what energy is or means might seem entirely different. If you ask an engineer or biologist for a definition of the word, however, you will probably receive the same, beautifully universal definition. Energy is, at its simplest, the capacity to do work. Whether the source is wind or complex proteins stored in a lynx’s breakfast, the potential to accomplish some task (such as twirling the blades of the Haeckel Hill wind-turbines or rebuilding damaged muscle tissue) remains fixed.

Now, with a clear definition of energy in mind, let’s return to that elusive and hypothetical suggestion made by our local biologist; winter has arrived, our energy bill is rising, but as humans, we aren’t alone in this experience. If energy is the capacity to do work, then what work is it that we and other animals require more of during the winter than other seasons? Although there may be a few answers to this  question, I’d argue that the most fitting one is probably the largest contributor to your monthly energy expenses this month: you guessed it, generating heat.

just as keeping warm comes with financial or time costs for humans, it also comes with energetic and nutritional costs for most other animals

For us humans, this typically means gathering wood, purchasing propane, or upping our electricity usage to keep our rooms comfortably warm throughout the short days and long evenings. For most other animals in the area (with a small caveat discussed below), generating heat means eating more and more often, shivering regularly, and hunting more frequently to warm their bodies through the processes of digestion and movement. So, just as keeping warm comes with financial or time costs for humans, it also comes with energetic and nutritional costs for most other animals; we pay in dollars, while the resident coyote pays in mice. An important thing to remember here is that maintaining a relatively constant and elevated body temperature is essential for survival for most animal species (ourselves included). That means that neither we nor they can easily or safely skimp on payments.

As you might expect, however, comparing costs of winter-living between us and our neighbourhood animals (in biology, we call them “sympatric” animals) isn’t so simple. As many readers may know, not all animal species are capable of producing body heat at the expense of food (a trait known as “endothermy”), and for those that are, the costs of doing so can vary quite dramatically. Thankfully, most all animal species that you’re likely to observe during a Yukon winter are indeed endotherms, so we can simplify our discussion by ignoring the other types (called “ectotherms”) from here on. Variability in the costs of keeping warm among species, however, is something we certainly can’t ignore. In fact, in my opinion, it’s in this variability where things truly become interesting. To help you side with me, take a look at the figure below that compiles energy consumption data collected by both Yukon Energy and a horde of poorly paid wildlife biologists.

Graph comparing energy consumption trends between Yukon species and average Yukon dwelling.

Because energy is surprisingly universal (as we discussed above) we can conveniently measure and display energy consumption for various animal species and a residential household using the same units (here, watts, or “W”: a measure of power). Before attempting to interpret this figure, first ignore the differences in vertical position of each line representing an animal species or household; these average differences in position are mostly explained by the (somewhat boring) differences in size among entities. Instead, take a close look at the overall differences between energy consumption in the cold (the far left) and the warmth (the far right) for each line/animal. These differences provide a fairly reliable measure of the relative costs of keeping warm for each species during cold months –  more commonly referred to as their costs of “thermoregulation”. Next, try considering the slopes of each line. As the inverse of our difference values, these slopes provide a reasonable indication of how efficiently heat is stored by a given species, where steep slopes represent relatively low heat-storage efficiency, and levelled slopes represent relatively high heat-storage efficiency.

Now, what you should have noticed is that for some species (the black-capped chickadee, black-billed magpie, and least weasel) the relative costs of thermoregulation in the cold can be quite high, and the relative heat-storage efficiency can be terribly poor. In chickadees, for example, costs of thermoregulation can reach over 70% of total energy expenditure on a given day, probably owing to their relatively poor ability to capture and preserve heat that is generated by their bodies (indicated by the steep slope of their line). More on chickadees here!

By contrast, for other species (the red fox and mule deer), the relative costs of thermoregulation in the cold can be shockingly low, and heat-storage efficiency shockingly high. The nearly-flat line associated with the red fox, for example, suggests that this species barely spends a mouse-worth of calories keeping warm at temperatures below -20°C, and is probably able to store most heat that is generated by its body. Furthermore, the curved line associated with the mule deer indicates that at temperatures above approximately 5°C, this species actually spends energy on getting rid of heat, not keeping warm, thanks to heat-storage efficiency being almost problematically high! Perhaps most impressively, however, is the average difference in slopes between animals and the residential home. From this difference, it appears that despite advanced insulation and/or double-brick walls, the relative costs of keeping our homes warm actually well-exceed those associated with many other animal species keeping themselves warm. Nevertheless, we should interpret household trends with caution given that use of electrical devices other than space-heaters or baseboard heaters (e.g. lights) may also increase in colder months, therefore further driving up total energy consumption.

At this point, you’re probably asking one of two questions:

  1. Why do we see such differences in costs of thermoregulation and heat-storage efficiency across animal species, or
  2. How do we, and not our houses, compare with these species for both traits?

These questions are something that Jake Paleczny (Executive Director at the Yukon Wildlife Preserve) and myself had been captivated by for quite some time. So, last winter, he and I equipped ourselves with an infra-red themographic camera and went to seek answers during a fortunately-timed cold snap at the preserve. 

Picture of Joshua Robertson at the Yukon Wildlife Preserve.

With our camera, we were able to remotely measure and quantify the amount of heat lost to the environment (again, in W) by both ourselves and the animals cared for at the preserve. From there, we were then able to compare relative heat-storage efficiency between different animal species and ourselves, and estimate just how much energy in food (measured by number of MacDonald’s cheeseburgers) we and other species might need to counterbalance energy lost in heat during the cold snap. Results of these estimations, will be detailed in the next post in this series, but for now, I’ll leave you readers with a few telling images (below) and a piece of a cheeseburger.

On the left is an infrared thermographic image of Jake that was captured while he was walking near the mule deer enclosure. The colours in this image represent the temperature of an object’s surface; the warmer the object, the brighter the colour (as indicated by the scale bar). To the right is a thermographic image of a thinhorn sheep (commonly known as a Dall sheep). The air temperature at which both images were taken averaged around -12°C – a modest winter day. Bear in mind that Jake is wearing a winter jacket and thermal lining underneath it, while the sheep is wearing its usual attire.

Now, if Jake were to have remained outside at the preserve for 4 hours, the amount of heat lost across his exposed face alone (the remainder of his body excluded) would amount to about a tenth of a cheeseburger. The thinhorn sheep? Well, we’ll have to get to that next time.

Joshua Robertson

Joshua Robertson

Behavioural and Physiological Ecologist

Joshua is a behavioural and physiological ecologist currently living on Cape Breton Island, Nova Scotia. During his PhD at Trent University, Joshua sought to understand how small birds can cope with the high costs of body temperature regulation when challenged with other environmental stressors (such as human and predator exposure). He is currently extending the research to better understand energy management strategies in warm-blood animals.

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