Mary McDonald / Masai giraffe {Giraffa camelopardalis} mother nuzzling baby, Lower Masai Mara GR, Kenya

Suzi Eszterhas / Leopard (Panthera pardus) six-week-old cub nuzzling mother, Jao Reserve, Botswana

Winfried Wisniewski / African Lion (Panthera leo) males nuzzling, Masai Mara, Kenya

Donald M. Jones / Black-tailed Prairie Dog (Cynomys ludovicianus) pair greeting, South Dakota

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

Marion Vollborn/ BIA / Tiger (Panthera tigris) female with cubs, native to Asia

Neil Aldridge / Warthog (Phacochoerus africanus) with a Yellow-billed oxpecker (Buphagus africanus) on its back, nuzzling its mother at a waterhole, Chief's Island, Okavango Delta, Botswana.

Tony Wu / Humpback whale (Megaptera novaeangliae) calf nuzzling its mother, Vava'u, Kingdom of Tonga, Pacific Ocean.

Richard Du Toit / Burchell's Zebra (Equus burchellii) pair nuzzling, Rietvlei Nature Reserve, South Africa

Richard Du Toit / Burchell's Zebra (Equus burchellii) females nuzzling, Rietvlei Nature Reserve, South Africa

Richard Du Toit / African Lion (Panthera leo) males greeting, Kgalagadi Transfrontier Park, South Africa

Richard Du Toit / Burchell's Zebra (Equus burchellii) parents tending to foal, Rietvlei Nature Reserve, South Africa