DOC WHITE / Blue whale underwater close-up of head and mouth feeding with pouch inflated, Mexico

Doc White / Blue Whales (Balaenoptera musculus) throat inflated, filter feeding at sea surface. California, USA. Sequence 1 of 2.

Ole Jorgen Liodden / Magnificent Frigatebird (Fregata magnificens) male displaying, red throat pouch inflated. Galapagos

Ole Jorgen Liodden / Magnificent Frigatebird (Fregata magnificens)displaying in flight, red pouch inflated. Galapagos

Rolf Nussbaumer / Couch's Spadefoot (Scaphiopus couchii) adult at night calling with vocal sac inflated. Laredo, Webb County, South Texas, USA, April.

Thomas Marent / European Tree Frog (Hyla arborea) calling, Switzerland

Wild Wonders of Europe / Schandy / European green toad (Bufo viridis) calling, vocal sac inflated, in a pond (at 2,711m) Adylsu valley, side valley to Baksan valley and Elbrus, Caucasus, Russia, June 2008

Wild Wonders of Europe / Schandy / European green toad (Bufo viridis) calling, vocal sac inflated, with eyes closed, in a pond (at 2,711m) Adylsu valley, side valley to Baksan valley and Elbrus, Caucasus, Russia, June 2008

Patrick Morris / Magnificent frigate bird {Frigata magnificens} pair on nest, male displaying with red throat pouch inflated, Genovesa Is, Galapagos

PREMAPHOTOS / Red-eyed tree frog (Litoria chloris) male with inflated throat sac, calling at night. Queensland, Australia

PREMAPHOTOS / Red-eyed tree frog (Litoria chloris) male with inflated throat sac, calling at night. Queensland, Australia

Juergen Freund / Close up of face of inflated pufferfish {Arothron sp}, Indo-Pacific