Mark Raycroft / English Bulldog (Canis familiaris) female running

Donald M. Jones / Rocky Mountain Elk (Cervus canadensis nelsoni) bull running, North America

Vincent Grafhorst / Hippopotamus (Hippopotamus amphibius) bull charging in territorial display, Botswana

Vincent Grafhorst / Hippopotamus (Hippopotamus amphibius) bull charging in territorial display, Botswana

Jean E. Roche / Bull run, with Camargue bulls leaping over hay bales, Camargue, France, July 2012.

Michio Hoshino / Alaska Moose (Alces alces gigas) bull charging, Alaska

Mark Raycroft / Elk (Cervus elaphus) bull running, North America

Ingo Arndt / Svalbard Reindeer (Rangifer tarandus platyrhynchus) males running in snow, Svalbard, Spitsbergen, Norway

Ingo Arndt / Svalbard Reindeer (Rangifer tarandus platyrhynchus) males running and jumping in snow, Svalbard, Spitsbergen, Norway

Ingo Arndt / Svalbard Reindeer (Rangifer tarandus platyrhynchus) male running in snow, Svalbard, Spitsbergen, Norway

Donald M. Jones / Elk (Cervus elaphus) bull running through river, western Canada

Donald M. Jones / Barren-ground Caribou (Rangifer tarandus groenlandicus) bull running, central Alaska