Erlend Haarberg / Arctic fox (Alopex lagopus) adult barking on rocks, Dovrefjell-Sunndalsfjella National Park, Norway, July.

Mark Taylor / Muntjac Deer (Muntiacus reevesi) fawn in studio conditions, in profile.

Donald M. Jones / Black-tailed Prairie Dog (Cynomys ludovicianus) standing and barking, eastern Montana

Wild Wonders of Europe / O. Haar / Arctic fox (Vulpes / Alopex lagopus) barking, dark summer phase, Hornstrandir, Iceland, July 2008

Wild Wonders of Europe / O. Haar / Arctic fox (Vulpes / Alopex lagopus) barking in a wild flower meadow, dark summer phase, Hornstrandir, Iceland, July 2008. WWE INDOOR EXHIBITION

Wild Wonders of Europe / O. Haar / Arctic fox (Vulpes / Alopex lagopus) barking in a wild flower meadow, dark summer phase, Hornstrandir, Iceland, July 2008

Ingo Arndt / Leopard Seal (Hydrurga leptonyx) barking, Weddell Sea, Antarctica

Doug Wechsler / Barking treefrog (Hyla gratiosa) male singing. Blackbird State Forest, Delaware, USA

Tim Fitzharris / Timber Wolf (Canis lupus) pair howling in snow, North America

Gerry Ellis / Common Barking Gecko (Ptenopus garrulus) licking its eye, Kalahari Desert, Botswana

Norbert Wu / California Sea Lion (Zalophus californianus) swimming underwater with mouth open in threat display, California

Jim Brandenburg / Black-tailed Prairie Dog (Cynomys ludovicianus) barking while standing atop burrow, South Dakota