Why do bull elk grow an eye-crater during the rut?

In Elk Facts by Kasey Rahn8 Comments

Courting is all about impressing the ladies, but if you’re looking to attract an elk cow, you might want to send pheromones in lieu of flowers. Bulls use many means of advertisement to attract females—the louder, showier and smellier the better. Behaviors like bugling, urine spraying, wallowing and destroying vegetation with their antlers grab a cow’s attention in obvious ways. A subtler part of the advertisement is the release of pheromones from the preorbital gland.

The quarter-moon shaped slit immediately forward of an elk’s eye houses this strange gland. During the rut, bulls open this slit to reveal the quarter-sized gland sometimes almost obscuring the bull’s eyes. The gland produces secretions containing pheromones, chemical messages sent to other animals of the same species that are meant to elicit a particular behavioral response.

Pheromones play different roles in the animal kingdom. Some might cause bees to swarm a predator, while others are used to direct a line of ants toward a food source. In many species, pheromones are also used to attract mates and to advertise sexual status.

A bull elk will often drag the side of his face along a branch as part of making an antler rub. This paints it with the bull’s unique secretions from the preorbital gland, including pheromones, as a way to communicate his sexual status. It’s just another—though quieter—way for a bull to say, “Hello ladies!”