Pedro Narra / Hippopotamus (Hippopotamus amphibius) with head raised above water surface, Bijagos Archipelago Biosphere Reserve, Guinea Bissau,

Staffan Widstrand / Hippopotamus (Hippopotamus amphibius) bull emerging from water to charge, iSimangaliso Wetland Park, KwaZulu Natal National Park. South Africa. Specially commended in the Animal Portraits category of...

Sharon Heald / Hippopotamus (Hippopotamus amphibius) charging, Chobe National Park, Botswana, July.

Sharon Heald / Hippopotamus (Hippopotamus amphibius) charging, Chobe National Park, Botswana, July.

Enrique Lopez-Tapia / Hippopotamus (Hippopotamus amphibius) charging against boat on Lake Chamo. Nechisar National Park. Ethiopia, November 2014

Ole Jorgen Liodden / Hippopotamus (Hippopotamus amphibius) rearing head out of water, creating spray, Lake Naivasha, Kenya.

Terry Whittaker / Young Water voles (Arvicola amphibius) on old pump wheel, Kent, UK, October.

Terry Whittaker / Water vole (Arvicola amphibius) feeding at edge of water, Kent, UK, December.

Hiroya Minakuchi / Hippopotamus (Hippopotamus amphibius) calves, Okavango Delta, Botswana

Ammonite / Group of sub-adult African lions (Panthera leo) chasing and jumping on a mother Hippopotamus (Hippopotamus amphibius) and her calf, footage taken at night using infrared camera technology, Masai Mara,...

Ammonite / Sub-adult African lioness (Panthera leo) chasing and jumping onto the back of a Hippopotamus (Hippopotamus amphibius), footage taken at night using infrared camera technology, Masai Mara, Kenya.

Vincent Grafhorst / Hippopotamus (Hippopotamus amphibius) bull marking territory by flicking dung, Chobe National Park, Botswana