Andy Rouse / Agile wallabies (Macropus agilis) sparring and fighting, Bamarru Plains, Northern Territories, Australia

Anup Shah / Adolescent male Lions (Panthera leo) play fighting, Masai Mara National Reserve, Kenya, March

Winfried Wisniewski / African Elephant (Loxodonta africana) males sparring, Chobe National Park, Botswana

Richard Du Toit / Burchell's Zebra (Equus burchellii) males sparring, Itala Game Reserve, South Africa

Suzi Eszterhas / Burchell's Zebra (Equus burchellii) stallions sparring, Masai Mara, Kenya

Richard Du Toit / Burchell's Zebra (Equus burchellii) stallions sparring, Savuti, Chobe National Park, Botswana

Richard Du Toit / Male Warthogs {Phacochoerus aethiopicus} sparring, Moremi WR, Botswana

Anup Shah / African elephants sparring {Loxodonta africana} trunks entwined, Serengeti NP, Tanzania

Anup Shah / African elephants sparring {Loxodonta africana} Serengeti NP, Tanzania

Anup Shah / African elephants sparring {Loxodonta africana} Serengeti NP, Tanzania

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) harem stallions posturing as prelude to fight, Montana

Matthias Breiter / Caribou (Rangifer tarandus) two males sparring, Denali National Park and Preserve, Alaska