Tim Fitzharris / Grizzly Bear (Ursus arctos horribilis) cub in snow, Idaho

Tim Fitzharris / Siberian Tiger (Panthera tigris altaica) running, native to Russia

Ingo Arndt / Timber Wolf (Canis lupus) running in snow, Minnesota

Ingo Arndt / Shoebill (Balaeniceps rex), Uganda

Ingo Arndt / Timber Wolf (Canis lupus) crossing river, Minnesota

Mark Carwardine / Yangtze / Chinese river dolphin / Baiji {Lipotes vexillifer} Critically endangered - officially declared extinct late 2007. This individual (a male called Qi-Qi) was photographed in captivity in 1988...

Claudio Contreras / American Flamingo (Phoenicopterus ruber) juveniles released from temporarty captivity, Ria Lagartos Biosphere Reserve, Yucatan Peninsula, Mexico.

Paul D Stewart / 'Martha' the last passenger pigeon, (Ectopistes migratorius), who died Cincinnati Zoo, September 1st, 1914. This portrait of her published in March 1915 as the Frontispiece to William Hornaday's 'The...

Jabruson / Mozambican children with captive Yellow Baboon youngster (Papio cynocephalus). Young animal caught during troop crop raiding. Pemba to Montepuez highway, north-eastern Mozambique, November 2011. Wildl...

Roland Seitre / Mother Iberian / Spanish Lynx (Lynx pardina) with cubs climbing the fence of their enclosure. Donana breeding station, part of the lynx reintroduction project in Andalusia. Spain, June 2006.

ZSSD / Rothschild Giraffe (Giraffa camelopardalis rothschildi), native to Africa

ZSSD / Rothschild Giraffe (Giraffa camelopardalis rothschildi) calf, native to Africa

ZSSD / Giant Anteater (Myrmecophaga tridactyla) young on mother's back, native to South America

ZSSD / Rothschild Giraffe (Giraffa camelopardalis rothschildi) mother and calf nuzzling, native to Africa

Hiroya Minakuchi / Beluga (Delphinapterus leucas) blowing toroidal bubble ring, Vancouver Aquarium, Canada

Konrad Wothe / Atlas Moth (Attacus atlas), native to southeast Asia

Chien Lee / Spotted-winged Fruit Bat (Balionycteris maculata) roosting, Bukit Sarang Conservation Area, Bintulu, Borneo, Malaysia

Pete Oxford / Chachi Tree Frog (Hypsiboas picturatus), northwest Ecuador

Pete Oxford / Northern Glassfrog (Hyalinobatrachium fleischmanni) underside showing internal organs, northwest Ecuador

Mark Carwardine / Northern white rhinoceros (Ceratotherium simum cottoni) with horn removed, after initial release into the wild, Ol Pejeta Conservancy, Kenya, June 2010, Extinct in the wild, only eight left in captivi...

Mark Carwardine / Northern white rhinoceros (Ceratotherium simum cottoni) close-up of eye, Dvur Kralove Zoo, Czech Republic, December 2009, Extinct in the wild, only eight left in captivity, critically endangered, Part...

Mark Carwardine / Northern white rhinoceros (Ceratotherium simum cottoni) close up of eye, in enclosure at Dvur Kralove Zoo, Czech Republic, the day before departure, December 2009, Extinct in the wild, only eight left...

Pete Oxford / Black-chested Buzzard-Eagle (Geranoaetus melanoleucus) juvenile, Podocarpus National Park, Ecuador

Jasper Doest / Ring-tailed Lemur (Lemur catta) mother with young, Netherlands

ZSSD / African Elephant (Loxodonta africana) calf stumbling, native to Africa

ZSSD / Blue and Yellow Macaw (Ara ararauna) pair flying, native to South America

ZSSD / African Lion (Panthera leo) male, native to Africa

ZSSD / African Lion (Panthera leo) male, native to Africa

ZSSD / Giant Panda (Ailuropoda melanoleuca) cub, native to China

Konrad Wothe / Bengal Tiger (Panthera tigris tigris), native to India

Michael Durham / Diving Beetle (Cybister fimbriolatus) jumping into water, photographed with a high-speed camera, central Texas

Albert Lleal / Red-footed Tortoise (Geochelone carbonaria), native to South America

Ingo Arndt / Amu-Darya Trout (Salmo trutta trutta) alevin freshly hatched with full yolk sac, Europe

Katherine Feng / Giant Panda (Ailuropoda melanoleuca), Xiang Xiang the first captive raised panda to be released into the wild, in pre release enclosure eating bamboo, Wolong Nature Reserve, endangered, China

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) 37 day old cub, Ying Ying, in incubator, Wolong Nature Reserve, endangered, China

ZSSD / Queensland Koala (Phascolarctos cinereus adustus) eating eucalyptus leaves, native to Australia

ZSSD / Rothschild Giraffe (Giraffa camelopardalis rothschildi) nuzzling calf, native to Africa

ZSSD / Sumatran Tiger (Panthera tigris sumatrae) cub, native to Sumatra

Matthias Breiter / Timber Wolf (Canis lupus) pair jumping over log, Montana

ZSSD / Queensland Koala (Phascolarctos cinereus adustus) in eucalyptus tree, native to Queensland

ZSSD / Bonobo (Pan paniscus) female playing with youngster by throwing him up in the air, native to Africa

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) scratching its head, native to Africa

ZSSD / Eclectus Parrot (Eclectus roratus) male, native to Australia and southeast Asia

ZSSD / Eurasian Lynx (Lynx lynx), native to Europe

Jasper Doest / Gray Wolf (Canis lupus) pair in the snow, Norway

Kevin Schafer / Mountain Lion (Puma concolor) cubs playing in snow, Utah

Kevin Schafer / Sumatran Tiger (Panthera tigris sumatrae) cub, endangered species native to Sumatra

Albert Lleal / Celebes Leaf Insect (Phyllium celebicum), native to southeast Asia

Nick Garbutt / Close-up of foot of chained domestic Asian Elephant (Elephas maximus) Royal Chitwan National Park, Nepal.

ZSSD / Blue Poison Dart Frog (Dendrobates azureus) very tiny poisonous frog, Indian tribes use poison for arrows, native to South America, San Diego Zoo, California

ZSSD / Bighorn Sheep (Ovis canadensis) male, native to North America, San Diego Zoo Safari Park, California

Hanne & Jens Eriksen / Arabian oryx {Oryx leucoryx} calf being released into the wild after captivity, Abu Dhabi

Hiroya Minakuchi / Flower Hat Jelly (Olindias formosa), native to Brazil, Argentina and Japan

Hiroya Minakuchi / Beluga (Delphinapterus leucas) whale trio blowing toroidal bubble rings, play behavior, vulnerable, Shimane Aquarium, Japan

Hiroya Minakuchi / Beluga (Delphinapterus leucas) whale trio calling, vulnerable, Shimane Aquarium, Japan

Tim Fitzharris / Gray Wolf (Canis lupus) pups in light snowfall, North America

Tim Fitzharris / Bobcat (Lynx rufus) mother and kitten, North America

Tim Fitzharris / Bobcat (Lynx rufus) mother and kittens, North America

Tim Fitzharris / Bobcat (Lynx rufus) mother and kitten in snowfall, North America

Tim Fitzharris / Siberian Tiger (Panthera tigris altaica) yawning, endangered, native to Siberia

Mitsuaki Iwago / Giant Panda (Ailuropoda melanoleuca), three captive bred cubs, China

Mitsuaki Iwago / Giant Panda (Ailuropoda melanoleuca) portrait, captive bred, Wolong, Sichuan, China

Mitsuaki Iwago / Giant Panda (Ailuropoda melanoleuca), captive bred cub, China

Theo Allofs / African Lion (Panthera leo) female portrait in rehabilitation center, Namibia

Theo Allofs / African Lion (Panthera leo) female portrait in rehabilitation center, Namibia

Michael Durham / Coho Salmon (Oncorhynchus kisutch) eggs at ten weeks after spawning, Washington

Pete Oxford / Peregrine Falcon (Falco peregrinus) portrait, Ecuador

Pete Oxford / Black-chested Buzzard-Eagle (Geranoaetus melanoleucus) juvenile, Ecuador

Pete Oxford / Chestnut-mandibled Toucan (Ramphastos swainsonii), Choco Forest, Ecuador

Albert Lleal / Giant Desert Hairy Scorpion (Hadrurus arizonensis) photographed under ultraviolet light showing fluoresence, native to southern North America and northern Mexico

Albert Lleal / Blue Poison Dart Frog (Dendrobates azureus) portrait, native to Surinam

Theo Allofs / Asian Elephant (Elephas maximus) 4 week old calf of a female trained as a working elephant for tourism and tiger tracking, India

Tim Fitzharris / Canada Lynx (Lynx canadensis) climbing on rock, North America

ZSSD / African Elephant (Loxodonta africana) calf portrait, threatened, native to Africa

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) baby clinging to mother's back, critically endangered, native to Africa

ZSSD / Giant Panda (Ailuropoda melanoleuca) cub in tree, endangered, native to China

ZSSD / Andean Cock-of-the-rock (Rupicola peruvianus) portrait, native to Andean cloud forests

ZSSD / Southern White-faced Owl (Ptilopsis granti) portrait, native to southern Africa

ZSSD / African Lion (Panthera leo) male and African Lioness, threatened, native to Africa

ZSSD / African Lion (Panthera leo) male portrait, threatened, native to Africa

ZSSD / Scarlet Macaw (Ara macao) pair kissing, native to South America

ZSSD / Rothschild Giraffe (Giraffa camelopardalis rothschildi) mother kissing calf, native to Africa

ZSSD / Rothschild Giraffe (Giraffa camelopardalis rothschildi) mother nuzzling calf, native to Africa

Matthias Breiter / Bobcat (Lynx rufus) walking in the snow, bobbed tail visible, Kalispell, Montana

Matthias Breiter / Mountain Lion (Puma concolor) in the snow, Kalispell, Montana

Yva Momatiuk & John Eastcott / California Condor (Gymnogyps californianus) adult with wingspan of 9 feet flying, critically endangered, bred in captivity, later released, and wearing radio transmitter, near Zion National Park, Utah

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) two cubs touching noses, Wolong Nature Reserve, China

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) cubs arranged to photograph all 16 cubs together, Wolong Nature Reserve, China, sequence 3 of 3

Konrad Wothe / California Sea Lion (Zalophus californianus) with mouth open in threat display blowing bubbles, North America

Tim Fitzharris / Raccoon (Procyon Lotor) two babies climbing tree, North America

Tim Fitzharris / Gray Wolf (Canis lupus) pair standing, North America

Tim Fitzharris / Gray Wolf (canis lupus) howling, North America

Tim Fitzharris / Mountain Lion (Puma concolor) mother carrying cub in her mouth, North America

Tim Fitzharris / Red Fox (Vulpes vulpes) kit, North America

Tim Fitzharris / Red Fox (Vulpes vulpes) trio of kits peeking out of their den, North America

Tim Fitzharris / Striped Skunk (Mephitis mephitis) kit, North America