Yukihiro Fukuda / Feral domestic rabbit (Oryctolagus cuniculus) standing on hind legs on coast, Okunojima Island, also known as Rabbit Island, Hiroshima, Japan.

Ross Hoddinott / Red fox (Vulpes vulpes) vixen yawning in the morning light (captive). Lifton, Devon, UK, May

Anup Shah / Cheetah cub and yawning mother (Acinonyx jubatus) Masai Mara, Kenya

Guy Edwardes / Hippopotamus (Hippopotamus amphibius) in Chobe River, Botswana.

Donald M. Jones / Yellow-bellied Marmot (Marmota flaviventris) yawning, central Montana

Nick Upton / Grey seal (Halichoerus grypus) pup aged one month, rubbing its head with its flipper, yawning and settling down to rest on a sandy beach, Norfolk, England, UK, January.

Ingo Arndt / Mountain gorilla (Gorilla gorilla berengei) yawning, showing stained teeth, Parc des Volcans, Rwanda

Ingo Arndt / Hamadryas baboon male threat display {Papio hamadryas} Africa

Ingo Arndt / Gelada baboon males threat display {Theropithecus gelada} Simien Mt NP, Ethiopia

Ingo Arndt / Gelada baboon male threat display {Theropithecus gelada} Simien Mt NP, Ethiopia

Neil Aldridge / Vervet monkey (Chlorocebus pygerythrus) yawning while sitting on a fallen tree in forests, Limpopo River, Kruger National Park, South Africa.

Neil Aldridge / Lioness (Panthera leo) yawning in early morning light on Kariega Game Reserve, South Africa.