ZSSD / East African River Hippopotamus (Hippopotamus amphibius kiboko) calf playing with mother underwater, San Diego Zoo, California

ZSSD / East African River Hippopotamus (Hippopotamus amphibius kiboko) 5 month old calf playing underwater, San Diego Zoo, California

ZSSD / East African River Hippopotamus (Hippopotamus amphibius kiboko) 5 month old calf with mother underwater, San Diego Zoo, California

Bruno D'Amicis / African hippopotamus (Hippopotamus amphibius). Blue Nile river, Bahir Dar, Lake Tana Biosphere Reserve, Ethiopia.

Denis-Huot / African elephant (Loxodonta africana) herd on bank of Mara River, with Hippos (Hippopotamus amphibius) in the water. Mara river, Masai-Mara Game Reserve, Kenya

Anup Shah / African elephant (Loxodonta africana) and Hippopotamus (Hippopotamus amphibius) on the banks of the Mara River. Maasai Mara National Reserve, Kenya.

Anup Shah / Hippopotamus (Hippopotamus amphibius) group sleeping on riverbank, Masai Mara, Kenya

ZSSD / East African River Hippopotamus (Hippopotamus amphibius kiboko) playing with calf, native to Africa

ZSSD / East African River Hippopotamus (Hippopotamus amphibius kiboko) mother with swimming calf, native to Africa

George Sanker / African elephant (Loxodonta africana) herd crossing the Mara River near a Hippopotamus (Hippopotamus amphibius) group, Masai Mara National Reserve, Kenya, January

Warwick Sloss / African lions {Panthera leo} feeding on hippo kill in drying river bed, Katavi NP, Tanzania.

Gerry Ellis / Hippopotamus (Hippopotamus amphibius) group resting on shore of Mara River, Masai Mara Reserve, Kenya