Neil Anderson / Red squirrel (Sciurus vulgaris), two curled up asleep in drey inside nest box. Nest of lichen and Pine needles. Highlands, Scotland, UK. Medium repro only.

Andy Rouse / Giant panda (Ailuropoda melanoleuca) cub aged five months falling asleep in a tree in a breeding centre, Chengdu, China. Captive.

Ingo Arndt / Gentoo Penguin (Pygoscelis papua) sleeping on beach, Volunteer Point, Falkland Islands, March

Francois Savigny / Polar bear and cub asleep on drifting iceberg, summer, Svalbard, Norway

Mark Taylor / Roborovski Hamster (Phodopus roborovskii) asleep sitting up, against white background

Diane McAllister,Diane McAllister / Japanese Macaque (Macaca fuscata) young one, appearing quite relaxed in thermal pool, even falling asleep, in Jigokudani, Japan, February

Dr. Axel Gebauer / Red panda (Ailurus fulgens), cub 4 days old in breeding den, captive

Chadden Hunter / Southern elephant seal (Mirounga leonina) close up of sleeping individual, South Georgia. Taken on location for BBC Frozen Planet series, 2008

David Woodfall / Bull Grey Seal (Halichoerus grypus) asleep in pool with reflection of bombing range sign in pool. Donna Nook, UK, November.

David Woodfall / Bull Grey Seal (Halichoerus grypus) asleep in pool with reflection of bombing range sign in pool. Donna Nook, UK, November.

Andy Sands / Dormouse (Muscardinus avellanarius) asleep in old Blackcap nest. Captive. UK, September.

Aflo / ic-02802 Two domestic cats sleeping with heads close together {Felis catus}