10 minute read

When you think of a moose, you might picture an iconic Canadian creature with long legs, a majestic set of antlers, and the undeniable air of someone who really doesn’t care about traffic. What might not come immediately to mind is the subtle yet striking neck accessory that moose wear with... well, little to no fanfare: the dewlap. Yes, that’s right—moose, with their immense size and serene grace, sport a fleshy flap of skin dangling beneath their throat.

If you've ever had the privilege (or slight anxiety) of encountering a moose here at the Yukon Wildlife Preserve, or on a cross-country road trip, you’ve maybe noticed this particular feature. But what is it, and why does it exist? Let’s explore this underappreciated anatomical feature with a mix of scientific curiosity and the lighthearted humor it deserves.

What is a Dewlap, Anyway?

A dewlap is essentially a flap of skin that hangs from the neck, or throat of an animal and while it may seem like just an odd fashion statement, it often serves practical purposes. Dewlaps appear in all kinds of animals—like lizards, cows, chickens, rabbits, and yes, moose. Depending on the species, dewlaps help with everything from sexual selection, to staying cool to general communication. In moose, the dewlap isn’t just a bizarre fashion accessory, it's also a multi-purpose tool in their biological toolkit - we think!

Watson on the left, Marsh on the right. 2023-making Watson 4 years old and Marsh 2 years old in this photo. Notice the dewlap difference?

Fun Fact: a dewlap on a moose is also called a bell. If you’re a bird, that fold of skin is called a wattle. For rabbits, dewlaps are basically nature’s way of saying, “Congrats, you’re all grown up now!” Female rabbits flaunt these fluffy neck pillows as a sign of sexual maturity. Later, when they have babies, they even pluck the thicker fur grown here to line the nest. Birds and reptiles, on the other hand, can take it up a notch with their flashy neck frills—bright, colorful, and often retractable like the world’s fanciest pop-up tent, perfect for showing off in romantic or territorial drama. 

Sitana ponticeriana. Photo by Niranjan Sant from Lizards in an Evolutionary Tree. 

But when it comes to ungulates, like moose, their dewlaps remain a mystery. It’s the unsolved cold case of the animal kingdom, stubbornly dodging scientific scrutiny. Nature can be funny like that sometimes.

Moose Practical Fashion: Is It About to Take Off?

Let’s address the most important question right off the bat: Do moose know they’re rocking a dewlap? Probably not. But if they did, we imagine it would make them feel pretty cool—like the one guest at a party with a trendy outfit no one else can pull off.  In the moose world, the dewlap is one of those things you don’t really see in everyday fashion. While antlers get all the glory in the animal kingdom, these enigmatic ornaments quietly steal the show in these hoofed animals. 

Moose, who roam the colder reaches of North America, use their dewlaps to help cool off in warmer weather. Male and female moose have dewlaps though their sizes differ considerably with, naturally, the male dewlap being larger than the females. The loose skin beneath their throat appears to expand and contract, and become more or less furry based on seasons which would help release heat from their bodies. This means that on a hot Yukon day (don’t worry, we don’t have too many of those), the dewlap might help prevent a moose from overheating as they browse lazily in the wild.

This statement might be contested by research from ungulates evaluated from Bro-Jørgensen given the need to thermoregulate (dissipate heat) is rather limited when you live in a more predominantly cold-climate than comparatively the eland antelopes of South Africa. Large ungulates like bison, elk, and yak do not present this caruncle; they may have evolved alternative, behavioural, cooling mechanisms that are less ‘cool looking’! But, wait, what about caribou? Technically, they fall under the 400kg threshold of the study and live in a cold climate and though they (males particularly) seem to rock the dewlap… sort of, theirs is more of a budget-friendly version compared to the moose’s deluxe mode.

(We’ll admit we’re pretty perplexed that both moose and caribou have flappy neck skin but wouldn’t be considered in the list of animals with evolutionary cooling mechanisms as they both are amazing swimmers, spending a lot of time in water and thus being able to cool themselves via this method—alas we will stick to moose necks!)  We appreciate that Bro-Jørgensen recognizes investigations into ungulate dewlap purposes has been left largely unexplored and for some reason, lizards have stolen all the scientists' attention. 

Dewlaps and Courtship: The Moose Dating Scene

If you thought moose were all about antlers for impressing mates, think again. Dewlaps are also, or alternatively to thermoregulation, thought to be involved in courtship. During mating season, male moose seem to have enlarged dewlaps to make themselves appear more impressive. After all, what’s a little extra neck real estate if it helps you woo the ladies? This trait can also be found in male leopards—alongside aging the dewlap grows, similar to a lion’s mane thickening, scientists believe this growth helps in intra and inter-specific interactions—the important sexual selection kinds of interactions for attracting mates and staving off competitors.

Moose Bull Watson in Summer 2024 and Winter 2024 show a side view of the animal and its dewlap. It appears larger by possibly being more hairy in the winter for protection of the extra skin. In summer lighter and able to dissipate heat like its less hair covered ears in the summer.

In some species (like lizards), males will flare their dewlaps out to signal dominance or interest in a mate. While moose don’t exactly go full "show-off" mode with their dewlaps, the extra skin could play a role in their mating rituals. After all, being a moose isn't all about looking tough with those antlers—it’s also about managing the subtler art of, well, neck presentation. 

These photos from young to old, left to right, are of Watson. We see from photos, the size of the dewlap appears to become larger over time. Bro-Jørgensen also explores the idea of the dewlap (in elands) being a detterent to predators as the side view makes the animal look larger and perhaps more intimidating. This would align with mature, genetically inclined animals having a larger dewlap. Though this was taken further and scarring on the dewlap was tested, exploring its advantages or disadvantages to protecting the common area of attack on prey by predators in some inter-species interactions.

A "Dewlap-umentary" Moment

Imagine a scene straight out of a nature documentary: A lone moose stands amidst the wild, its dewlap gently swaying in the wind as it scans the horizon. It’s a thing of beauty, really. But then, a rival moose appears on the scene—let the neck flap show begin! Not much behaviour present in ungulates, as seen in lizards and birds, but the moose may posture, showing off their large body size and then bam - side view of an impressive neck dangle and their rival runs away in fear - perhaps a convincing illusion.

Wrapping It Up: A Love Letter to the Dewlap

So, the next time you visit the Yukon Wildlife Preserve and you catch sight of a moose strolling majestically past, don't just look up at the antlers or marvel at their towering size. Look down (or, more accurately, look to the side) and take a moment to appreciate the dewlap. Despite all the brainpower spent pondering this, no one really knows why moose have dewlaps. Is it a fashion statement? A built-in scarf for chilly mornings? Who knows!

Since both male and female moose have them and they don't seem to offer any major survival or dating perks, scientists think basically, ungulates got their dewlaps through evolutionary peer pressure, but not the same kind as lizards and birds. While birds and lizards are out there with their flashy, look-at-me neck bling for dating or drama, ungulates might’ve evolved their dewlaps for totally different reasons—like a mysterious club no one’s quite figured out yet. The dewlap might just be a leftover from moose ancestors—like a trendy accessory that’s fallen out of style but still hangs around (sciencey talk calls this a vestigial trait).

In the world of wildlife, the moose's dewlap is mysterious, beautiful, and—if we’re being honest—just a little bit stylish. Who knew that this flappy neck skin would be so fascinating? Certainly not us. But we’re glad we found out. Wait, what exactly did we find out!?

Resources:

Bro-Jørgensen, J. Evolution of the ungulate dewlap: thermoregulation rather than sexual selection or predator deterrence?. Front Zool 13, 33 (2016). https://doi.org/10.1186/s12983-016-0165-x

Baeckens, Simon et al. “The brown anole dewlap revisited: do predation pressure, sexual selection, and species recognition shape among-population signal diversity?.” PeerJ vol. 6 e4722. 8 May. 2018, doi:10.7717/peerj.4722

Jonathan Losos. How Many Times have lizard Dewlaps Evolved? August 12, 2011.

Photo credits: L.Caskenette, J.Benjamine, J.Paleczny, M. Mark., (unless otherwise noted).