Mule deer in Rocky Mountain National Park

Mule Deer Rut

Close up of a mule deer in Estes Park
Mule Deer exposing his Jacobson’s Organ in the roof of his mouth. Photo: Jared Gricoskie

Imagine a guy walks into a bar and asks all the ladies if anyone is fertile. In the hooved animal world, that is what males, such as mule deer, do during the “Rut” mating season. This Mule Deer  pictured is exposing his Jacobson’s (Vomeronasal) Organ in the roof of his mouth. This is, basically, a fertility test to smell if any females are in Estrus, the fertility period. The doe releases her estrus advertising her upcoming fertility of just a few hours to attract as many males as possible so she can select the best mate. The buck’s main job during the rut season is to run around his range lip curling to expose his Jacobson’s Organ and investigate all the does to try focus on impressing only the girls who are fertile at that time.

The mule deer rut season in the Estes Park and Rocky Mountain National Park area is the end of November.

Written by Jared Gricoskie, a private guide for Estes Park tours
Yellow Wood Guiding

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