Richard Du Toit / Burchell's Zebra (Equus burchellii) flehming, Kwazulu Natal, South Africa

Winfried Wisniewski / African Lion (Panthera leo) female with male flehming, Masai Mara, Kenya

Tim Fitzharris / Siberian Tiger (Panthera tigris altaica) flehming, native to Russia

Winfried Wisniewski / Grant's Zebra (Equus burchellii boehmi) male flehming, Masai Mara, Kenya

Richard Du Toit / Burchell's Zebra (Equus burchellii) male smelling female amongst Pompom Weed (Campuloclinium macrocephalum), Rietvlei Nature Reserve, Gauteng, South Africa

Richard Du Toit / Burchell's Zebra (Equus burchellii) flehming, Rietvlei Nature Reserve, Gauteng, South Africa

Richard Du Toit / African Lion (Panthera leo) male flehming, Kruger National Park, South Africa

Richard Du Toit / Burchell's Zebra (Equus burchellii) male flehming, Rietvlei Nature Reserve, Gauteng, South Africa

Donald M. Jones / American Bison (Bison bison) bull tasting air for receptive females, National Bison Range, Moise, Montana

Tui De Roy / Zebra (Equus quagga) stallion flehming to smell if female is receptive, Ol Pejeta Conservancy, Kenya

Mark Raycroft / White-tailed Deer (Odocoileus virginianus) buck flehming, North America

Mark Raycroft / Alaska Moose (Alces alces gigas) bull flehming, Alaska

Michael Quinton / Dall Sheep (Ovis dalli) ram flehming, Yukon Territory, Canada

Michael Quinton / Dall Sheep (Ovis dalli) rams flehming, Yukon Territory, Canada

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming, western Montana

Donald M. Jones / Moose (Alces alces shirasi) bull flehming, western Montana

Donald M. Jones / White-tailed Deer (Odocoileus virginianus) buck flehming, western Montana

Donald M. Jones / Pronghorn Antelope (Antilocapra americana) buck flehming, eastern Montana

Donald M. Jones / Pronghorn Antelope (Antilocapra americana) buck flehming, eastern Montana

Donald M. Jones / Pronghorn Antelope (Antilocapra americana) buck flehming, eastern Montana

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming, western Montana

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming, western Montana

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming, western Montana

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming, western Montana

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming, western Montana

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming with two does, western Montana

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming, western Montana

Donald M. Jones / Mule Deer (Odocoileus hemionus) buck flehming, western Montana

Donald M. Jones / Moose (Alces alces shirasi) bull flehming, western Montana

Donald M. Jones / American Elk (Cervus elaphus nelsoni) bull flehming, western Montana

Donald M. Jones / American Elk (Cervus elaphus nelsoni) bull flehming, western Montana

Donald M. Jones / Dall's Sheep (Ovis dalli) ram flehming, Yukon, Canada

Richard Du Toit / Burchell's Zebra (Equus burchellii) male flehming, Sabi-sands Game Reserve, South Africa

Winfried Wisniewski / Burchell's Zebra (Equus burchellii) male flehming, Masai Mara National Reserve, Kenya

Winfried Wisniewski / Burchell's Zebra (Equus burchellii) pair in the savannah, one of them flehming, Masai Mara National Reserve, Kenya

Mark Raycroft / White-tailed Deer (Odocoileus virginianus) buck flehming, North America

Theo Allofs / African Lion (Panthera leo) male flehming, Moremi Game Reserve, Okavango Delta, Botswana