Bull Elk (Cervus canadensis) with the Flehmen response during the rut, Jasper National Park, Alberta, Canada, North America

Bison (Bison bison) bull demonstrating the flehmen response, Yellowstone National Park, Wyoming, United States of America, North America

Desert Bighorn Sheep (Ovis canadensis nelsoni) ram in captivity exhibiting the Flehmen response, Arizona Sonora Desert Museum, Tucson, Arizona, United States of America, North America

Lion (Panthera leo) showing flehmen grimace, Zimanga private game reserve, KwaZulu-Natal, South Africa, Africa

Bull elk (Cervus canadensis) demonstrating the flehmen response, Jasper National Park, Alberta, Canada, North America

Lion (Panthera leo) demonstrating the flehmen response, Ngorongoro Conservation Area, UNESCO World Heritage Site, Serengeti, Tanzania, East Africa, Africa

A male lion (Panthera leo), doing the flehmen grimace, Tsavo, Kenya, East Africa, Africa

Bull elk (Cervus canadensis) demonstrating the flehmen response during the rut, Jasper National Park, UNESCO World Heritage Site, Alberta, Canada, North America

Lion (Panthera leo) demonstrating the flehmen response, Ngorongoro Conservation Area, UNESCO World Heritage Site, Serengeti, Tanzania, East Africa, Africa

Red deer, Cervus elaphus, stag, sniffing the air, Kingussie, Scotland

Red deer, Cervus elaphus, stag, sniffing the air, Kingussie, Scotland

White-tailed deer

Mouflon (Ovis ammon musimon), flehmen response during mating season

Lion (Panthera leo) . Male doing the flehmen response. Kalahari Desert, Kgalagadi Transfrontier Park, South Africa, Africa

Approached by a cow moose, a bull (Alces alces), displays the Flehmen response late in the rut in Southcentral Alaska's Chugach State Park, Anchorage, Alaska, United States of America

Bighorn Sheep ram (Ovis canadensis) performs lip curl (flehmen display) in the North Fork of the Shoshone River valley near Yellowstone National Park; Wyoming, United States of America

A male lion (Panthera leo) shows the Flehmen response by opening his mouth wide as if he were roaring. He has a golden coat that glows in the warm early morning light. Shot with a Nikon D850 in Serengeti National Park; Tanzania

White-Tailed Deer (Odocoileus Virginianus), Reddick, Florida, United States Of America

Lion (Panthera leo) Flehmen reaction, Masai Mara National Reserve, National Park, Kenya *** Local Caption *** walking in the grass by rolling up the lips to register the pheromones of female in heat with her Jacobson glands

Lion (Panthera leo). Male doing the flehmen response. Kalahari Desert, Kgalagadi Transfrontier Park, South Africa.

African Lion (Panthera leo) flehmen, Masai Mara, Kenya