Best of the Tetons, Great Photography Tours In Jackson, WY

October Bull

Flehmen Response or “Lip Curl” in GTNP Moose

During the fall rut, Moose commonly display a Flehmen Response—or lip curl. Anytime a moose bull smells the urine of a cow, you can expect a Flehmen Response to follow. Savvy photographers click away!

Flehmen Front View

In reality, “Flehmen is performed by a wide range of mammals including ungulates and felids.” (Click the link for more information at Wikipedia or do your own searches for technical definitions). Images on this page will include Moose, Wild Mustangs, Mountain Goats,  and Bighorn Sheep.  Elk and cats like Mountain Lions also perform a lip curl, even if I don’t have photos. The image above is typical of a bull moose in a Flehmen Response. The mouth is open with his head pointed high into the sky. Often, their eyes close, as in a trance. The whole event can last a roughly minute. According to Wikipedia, “The behavior facilitates the transfer of pheromones and other scents into the vomeronasal organ located above the roof of the mouth via a duct which exits just behind the front teeth of the animal.”

Bull in Velvet

Moose in Velvet: From my experiences watching moose in the fall, the big bulls show little interest in the cows before they strip their velvet. Bulls seldom spar or fight while still in velvet. Still, this bull felt the need to do an early season lip curl.

Early Fall

Early Fall: Most moose strip their velvet in September—a few days or a week either side of Labor Day. Leaves are still usually lime green as seen in this morning capture.

Fall Bull and Cow

Fall Bull and Cow: As fall progresses, a bull finds a potential mate and stays with her until she goes out of season, then he moves on to find another cow.

Young Bull

Young Bull: This bull is probably three years old and is already getting into the act. Prime cows will not let him breed, but he will still play out the fall routine. It is always nice to have a young bull in the area. They have much more energy and keep the larger bulls active running them away from their potential mate.


Fog: Weather doesn’t deter the fall rut. Rain, fog, snow, sleet…it doesn’t matter!

Moose Rut in the Stream

Moose Rut in the Stream: I’ve always been able to get my best moose images in the early mornings. They are active for about the first hour of light, then bed down for most of the warm and bright hours. Early morning steam added some character to this shot.

October Bull

October Bull: Bull moose cover a lot of ground searching for ready cows. This bull spent much of the early fall under the Snake River bridge at Moose Junction. Later, I found him at Schwabacher Landing, and again at the Shane Cabin. A few days later, he was along the Gros Ventre. I last saw him out in the sagebrush near Ditch Creek.

December Bull

December Bull: I photographed this nice bull on December 7th of 2013. Most of the rut is usually over by then, but bulls still display a Flehmen Response if they smell the urine of a cow.

Mountain Goat

Mountain Goat: Many other ungulates display a Flehmen Response during their fall rut.

Flehmen Response

Bighorn Ram: Both young and old rams do a “lip curl” as seen here.


Wild Mustang: I photographed this beat up old Mustang stallion near Rock Springs, WY.  Watch for a Flehmen Response in hooved animals (ungulates) and cats.

Bison Lip Curl

American Bison: (Sometimes still called Buffalo) Bison are usually into the swing of the rut period during the month of August.

I am probably prejudiced, but I think Flehmen Responses in Moose and Elk are probably the most dramatic. Their large antlers roll back as their noses reach for the sky.


Please note: Images on this page are fully protected with an official copyright at the US Copyright Office.  No unauthorized use is granted.

If you like this post, please take the time to click any of the Social Media icons below and share the page with your friends and associates. Hope you enjoy the images and comments. Cheers! Mike Jackson

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Comment (1)

  1. Lowell Schechter

    Hi Mike
    It must be fascinating to see these animals habits such as this. Makes for great watching and photographing this ritual

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