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Dewlap

Bull Moose Sexually Advertising

10-12-15 moose 20090924-01 080As part of the rut, or breeding season, that they are in the middle of, bull moose seek to advertise their wares as far and as wide as possible. Information regarding the moose’s dominance is conveyed visually to cow moose (as well as other bull moose) by the size of a bull moose’s antlers. Additional information is conveyed olfactorily through the transfer of urinary pheromones via the bull moose’s bell, or dewlap (structure located under the chin of both bull and cow moose).

A moose’s bell increases in size with age (the pictured moose is just a yearling). While there are many theories as to the function of the bell (thermoregulation during the heat of summer, extra insulation for a moose’s chin when bedding down in snow and a secondary indicator of sex and age), it has been confirmed that the bell is an olfactory device that plays a role in communication.

During rut a bull often digs a depression (wallow) in the ground in which he urinates. He then proceeds to stamp and wallow in this depression, thoroughly soaking his antlers, belly and bell with his pheromone-laden urine. Cows are attracted to this pungent scent. Suspended from the bull’s body, the bell is an excellent way of dissipating these pheromones into the air – an innovative means of sexual advertising.

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