Donald M. Jones / Northern Pintail (Anas acuta) males flying with female in spring courtship display, Montana

Donald M. Jones / Bighorn Sheep (Ovis canadensis) female and male in winter, Jasper National Park, Alberta, Canada

Chien Lee / Minden / Stick Insect (Monticomorpha flavolimbata) pair mating in mountains, Bengoh Range, Ecuador

Donald M. Jones / Bighorn Sheep (Ovis canadensis) ewe and ram, western Montana

Michael Quinton / Dall's Sheep (Ovis dalli) ram, lamb, and ewe, Yukon Territory, Canada

Luciano Candisani / Green Anaconda (Eunectes murinus) female constricting male after copulation, after which she will consume him, Brazil

Alan Murphy/ BIA / Northern Bobwhite (Colinus virginianus) female and male, Texas

Brais Seara Fernandez/ BIA / Indian Peafowl (Pavo cristatus) female watching male performing courtship display, Castilla Leon, Spain

Donald M. Jones / Elk (Cervus elaphus) bull and harem of females and calves along river, Athabasca River, western Canada

Donald M. Jones / Bighorn Sheep (Ovis canadensis) rams, ewe, and lamb, western Canada

Rick Bowers/ BIA / Gambel's Quail (Callipepla gambelii) male at left with female, Arizona

Thomas Marent / Gelada Baboon (Theropithecus gelada) male and females huddling for warmth, Simien Mountains National Park, Ethiopia