Dangling Dewlaps

BY Mark McCollough

The Indians called it mousomodai, meaning literally ‘Moose bottle.” You may refer to it as the bell. In 1909 Ernest Thompson Seton in Lives of Game Mammals wrote, “A marked peculiarity in the Moose, male and female, is the bell on the throat. I have examined many of these in the newly killed specimens, and in the living animal: and could find nothing in them but a long dewlap of skin with appropriate blood vessels. Sometimes it is round; sometimes flat, lying along the way; sometimes flat the cross way of the animal’s throat; sometimes simple; sometimes forked; sometimes hanging from the jaw, and sometimes from a long blade-like dewlap, but always without discernable scent glands. I have squeezed and worked them with my hands on the living Moose, and have been unable to discover any smell or signs of exudation; or indeed, any specialization that would afford a hint of their purpose. No one yet has given any satisfactory explanation of this curious dangler.”

This fall, lucky Maine moose hunters will have a golden opportunity to fondle this curious dangler; although preferably not one from a living moose. The dewlap or bell is an unorthodox feature of the moose anatomy, yet no one seems to understand just what it is for.

In the 1800s, naturalists postulated this flap of hair and skin swaying under a moose’s chin either spread scent, kept a moose’s throat warm while lying in snow, or was just there for good looks. Some believed it once had a function that was lost long ago, but it is still hangs there as a vestigial organ, much the same as our appendix.

More recent theories abound. Female moose may assess a bull’s virility by the size of his pendulous bell. A bigger bell is allegedly better. Another theory is that during the rut, a bull rubs the cow’s flanks with his chin; a behavior called chinning. While engaged in this form of affection some believe the dewlap transfers the bull’s musky scent to the female. Perhaps the highly vascularized moose bell is there to cool the moose during the host summer months. Yet another speculation is that the size and shape of the dewlap and antlers is an indicator of dominance at the moose single’s bar.

Most of these theories don’t explain why cows also have a dewlap. In fact, the longest dewlap on record belongs to a female moose. Ordinarily, a good-sized bell is 8 to 10 inches long; 14 inches would be exceptional even for a bull. But in 1897, a Manitoba Indian brought a cow moose to a taxidermist shop in Winnepeg with a bell that was a whopping 38 inches long. Does your bell hang low, does it wobble to and fro…? At the insistence of the hunter, the taxidermist mounted the incomparable bell on a bull moose’s head.

Dewlaps come and dewlaps go. They are present on bulls and cows in utero. They grow as both sexes mature, and frequently sport a “tail,” which has a propensity to freeze and drop off from frostbite during the second to fourth winter of a moose’s life. For unknown reasons, woodland moose loose the tails on their dewlaps more frequently than their northern taiga brethren. Cow moose retain their tails more than bulls. Moose bells reach peak size when a bull is in his prime (4 to 6 years). With age the part of the dewlap closest to the neck broadens while the pendulous length shortens. They allegedly shrink with old age. Seton wrote of old dewlaps, “…it no longer answers any useful purchase.” If you don’t use it, you loose it.

In 1979, Lakehead University wildlife student, “Tim” Timmermann, was the first to delve into the science of dewlaps and wrote an entire master’s thesis on the subject. He carefully dissected dewlaps and found them heavily vascularized with blood vessels and full of sebaceous (sweat) glands, but no scent glands. Since then a handful of scientists have pondered the mysteries of the bell, dissected dewlaps to unravel their riddles, and observed moose using their pendulous protuberances. Two competing hypotheses have emerged. First, bull moose lather their bells with slobber and urine to impress females during the rut. This is somewhat like hunters basting themselves with Old Spice before returning to their wives from hunting camp. Coy cows roll in a bull’s wallow and rub against his bell, which may stimulate ovulation. Theory number two is that the bell evolved as a secondary sex characteristic that conveys information on sex and age to other moose, especially during the winter when the antlers are not present.

Bull caribou and elk sport manes possibly for the same purpose.

To test the first hypothesis, scientists studied wallowing behavior of moose in Denali National Park. Bulls make wallows, pee in them, and roll in the testosterone-laden perfume. Female moose frequented and rolled rolled in wallows made by rutting bulls. Rutting cows and bulls touch noses and rubbed rumps far more frequently than other regions of the body, including the bell. Chinning was a relatively rare behavior. Hypothesis one was rejected. The bell did not seem to play a unique role in dispersing the pungent stench of a rutting bull.

To test the hypothesis that the size and shape of the bell communicates social status and sex, researchers observed moose and classified their bells according to 8 different “Timmermann bell classes.” (All wildlife graduate students dream of becoming this famous.) They recorded the size and shape of dewlaps of bulls and cows during antagonistic encounters, especially during the rut. Small-antlered bulls had long, skinny dewlaps with tails. Large-antlered bulls had large, pendulous bells with no tails. However, bell size and shape had no bearing on the outcomes of spats between bulls or cows. Although the shape of the bell may be a way for moose to gauge each other’s age (tail or no tail on the bell), it seems unlikely that nature would select for a characteristic that was susceptible to frostbite. Therefore, the jury remains out on hypothesis number two. Perhaps some aspiring wildlife biologist will rise to fame and unlock the mystery of the dangling dewlap.

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Mark McCollough has been on many moose hunts with friends from Hampden, Maine. The tail of his dewlap froze and fell off years ago. He can be reached at [email protected]

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