A cheetah resting on an old termite mound, Moremi Game Reserve, Botswana, Africa.

Young Hedgehog sleeping on dead leaves, Corsica France

Female and young hippo lying on the bank, Kruger

Cat and kitten sleeping on a sidewalk, Essaouira, Morocco

Snorkeler photographing a pod of Sleeping sperm whale (Physeter macrocephalus) Researchers first saw this unusual sleep behavior in sperm whales in 2008. The scientists in that study found that sperm whales dozed in this upright drifting posture for about 10 to 15 minutes at a time, Vulnerable (IUCN). The sperm whale is the largest of the toothed whales. Sperm whales are known to dive as deep as 1,000 meters in search of squid to eat. Dominica, Caribbean Sea, Atlantic Ocean. Photo taken under permit n°RP 16-02/32 FIS-5.

Pod of Sleeping sperm whale (Physeter macrocephalus) Researchers first saw this unusual sleep behavior in sperm whales in 2008. The scientists in that study found that sperm whales dozed in this upright drifting posture for about 10 to 15 minutes at a time, Vulnerable (IUCN). The sperm whale is the largest of the toothed whales. Sperm whales are known to dive as deep as 1,000 meters in search of squid to eat. Dominica, Caribbean Sea, Atlantic Ocean. Photo taken under permit n°RP 16-02/32 FIS-5.

Free diver is swimming over a pod of Sleeping sperm whale (Physeter macrocephalus) Researchers first saw this unusual sleep behavior in sperm whales in 2008. The scientists in that study found that sperm whales dozed in this upright drifting posture for about 10 to 15 minutes at a time, Vulnerable (IUCN). The sperm whale is the largest of the toothed whales. Sperm whales are known to dive as deep as 1,000 meters in search of squid to eat. Dominica, Caribbean Sea, Atlantic Ocean. Photo taken under permit n°RP 16-02/32 FIS-5.

Pod of sperm whale relaxing after a short sleep (Physeter macrocephalus) Researchers first saw this unusual sleep behavior in sperm whales in 2008. The scientists in that study found that sperm whales dozed in this upright drifting posture for about 10 to 15 minutes at a time, Vulnerable (IUCN). The sperm whale is the largest of the toothed whales. Sperm whales are known to dive as deep as 1,000 meters in search of squid to eat. Dominica, Caribbean Sea, Atlantic Ocean. Photo taken under permit n°RP 16-02/32 FIS-5.

Sleeping sperm whale, (Physeter macrocephalus), Vulnerable (IUCN), The sperm whale is the largest of the toothed whales. Sperm whales are known to dive as deep as 1,000 meters in search of squid to eat. Image has been shot in Dominica, Caribbean Sea, Atlantic Ocean. Photo taken under permit n°RP 16-02/32 FIS-5.

Pod of Sleeping sperm whale (Physeter macrocephalus) Researchers first saw this unusual sleep behavior in sperm whales in 2008. The scientists in that study found that sperm whales dozed in this upright drifting posture for about 10 to 15 minutes at a time, Vulnerable (IUCN). The sperm whale is the largest of the toothed whales. Sperm whales are known to dive as deep as 1,000 meters in search of squid to eat. Dominica, Caribbean Sea, Atlantic Ocean. Photo taken under permit n°RP 16-02/32 FIS-5.

Leopard (Panthera pardus pardus), in a tree where its prey is, Masai Mara National Reserve, National Park, Kenya

Ringed seal at rest on ice, Barter Island Alaska USA

Crabeater seal (Lobodon carcinophaga) resting on an ice floe, Antarctica, Antarctic Peninsula, Portal Point

Spotted hyena (Crocuta crocuta), adult and young, resting on the ground at the entrance of the den, Masai Mara National Reserve, National Park, Kenya

South American sea lion (Otaria flavescens) resting on a dock of Port Stanley, Falkland

Polar bear (Ursus maritimus) Twin polar cubs on their mother's back. Churchill, MB, Canada,

Spotted hyena (Crocuta crocuta), adult and young, resting on the ground at the entrance of the den, Masai Mara National Reserve, National Park, Kenya

Close up portrait of a lioness, Panthera leo, sleeping. Masai Mara National Reserve, Kenya.

Bornean Sun Bear (Helarctos malayanus) at rest on a branch, Borneo Malay Bear Center, Rescue and Rehabilitation Center, Sepilok Rehabilitation Center, Sabah, Malaysia, North Borneo, Southeast Asia

Elephant seal females sleeping, Maquarie Island Australia

Crabeater Seal (Lobodon carcinophaga), resting on ice floe. Antarctica, Antarctic Peninsula, Detaille Island

Eye of a common parrot fish (Scarus psittacus) sleeping at night on a Sudanese reef in the Red Sea.

Proboscis Monkey on trunk, Labuk Bay Sabah Borneo Malaysia

Tawny owl (Strix aluco) under a tile shelter, Forest National Park, Haute-Marne, France

Two lionesses (Panthera leo) are lying on a big tree. Close-up. Uganda. East Africa.

Lionesses (Panthera leo) lying on a big tree. Close-up. Uganda. East Africa.

Polar bear sleeping on the back, Barter Island Alaska

Cape fur seal (Arctocephalus pusillus), Cape Cross, Namibia

Southern Fur Seal at rest, Punta San Juan Peru

Leopard (Panthera pardus), female at rest, Masai-Mara National Reserve, Kenya

Meerkat resting on sand