Mark Raycroft / Border Collie (Canis familiaris) adult with three tennis balls in its mouth, waiting to play fetch

TJ Rich / Black Labrador head portrait with collar and tag, Wiltshire, UK

Jean E. Roche / Cory's shearwater (Calonectris diomedea) juvenile with dark fluff collar on the head, handled by scientist during bird ringing. Frioul archipelago, Marseille, France.

Ernie Janes / Domesticated Bactrian camels (Camelus bactrianus) with colourful halters, used for camel racing England, UK.

Ernie Janes / Domesticated Bactrian camels (Camelus bactrianus) with colourful halters, used for camel racing England, UK.

Ernie Janes / People racing on domesticated Bactrian camels (Camelus bactrianus) with colourful halters. England, UK.

Sumio Harada / Mountain Goat (Oreamnos americanus) collared nanny grazing on Snow Cinquefoil (Potentilla nivea), Glacier National Park, Montana

Sebastian Kennerknecht / Mountain Lion (Puma concolor) biologists, Max Allen and Paul Houghtaling, placing radio collar on six week old male cub, Santa Cruz Puma Project, Santa Cruz, Monterey Bay, California

Sebastian Kennerknecht / Mountain Lion (Puma concolor) biologists, Max Allen and Paul Houghtaling, placing radio collar on six week old male cub, Santa Cruz Puma Project, Santa Cruz, Monterey Bay, California

Cyril Ruoso / Chacma Baboon (Papio ursinus) alpha male wearing collar so the troop can be tracked to try and avoid human conflict, South Africa

Mark Raycroft / Rhodesian Ridgeback (Canis familiaris) puppy

Mark Raycroft / Black Labrador Retriever (Canis familiaris)

Mark Raycroft / Boxer (Canis familiaris)

Mark Raycroft / Boston Terrier (Canis familiaris)

Laurent Geslin / Radio collared Leopard (Panthera pardus) head portrait in profile, Chobe National Park, Khawai, Botswana, Southern Africa

Petra Wegner / Standard Poodle, black coated and clipped with collar, head portrait, panting

Petra Wegner / Standard Poodle, black coated and clipped with collar, head portrait

Petra Wegner / Standard Poodle, black coated and clipped with collar, head portrait in profile

Petra Wegner / Standard Poodle, black coated and clipped with collar, head portrait, panting

Petra Wegner / Standard Poodle, black coated and clipped with collar, head portrait

Kristel Richard / Domestic horse, Portrait of a rare native bay Kiso stallion with head collar, standing in paddock, Kiso County, Nagano Prefecture, Japan.

Kristel Richard / Domestic horse, a rare native bay Kiso stallion with head collar, standing in paddock, Kiso County, Nagano Prefecture, Japan. 2009

Mark Taylor / Border Terrier bitch puppy, Kes, lying with head up.

Donald M. Jones / American Elk (Cervus elaphus nelsoni) cow with radio-collar and ear tag, western Alberta, Canada

Jane Burton / Staffordshire Bull Terrier pup, 18 weeks old, wearing a Halti head collar, led by Bradley (8 years old)

Jane Burton / Portrait of Yellow Labrador Retriever dog with head cocked to one side

Michael Durham / American Elk (Cervus elaphus nelsoni) two day old calf is outfitted with a radio collar by biologist Scott Findholdt with the Oregon Department of Fish and Wildlife, Sled Springs Study Area, northeast...

Michael Durham / Bighorn Sheep (Ovis canadensis) ram with radio collar, Wallowa Mountains, Oregon

Mark Raycroft / Cairn Terrier (Canis familiaris) puppy in play structure

Mark Raycroft / American Pit Bull Terrier (Canis familiaris) portrait

Mark Raycroft / American Pit Bull Terrier (Canis familiaris) portrait

Mark Raycroft / West Highland White Terrier (Canis familiaris) in basket

Mark Raycroft / Rhodesian Ridgeback (Canis familiaris) adult portrait

Mark Raycroft / Staffordshire Bull Terrier (Canis familiaris) with tennis balls

Mark Raycroft / Rhodesian Ridgeback (Canis familiaris) adult portrait

Mark Raycroft / Bullmastiff (Canis familiaris) adult reclining on lawn

Mark Raycroft / Rhodesian Ridgeback (Canis familiaris) portrait

Mark Raycroft / English Springer Spaniel (Canis familiaris) portrait on lawn

Mark Raycroft / Great Dane (Canis familiaris) portrait with natural ears

Mark Raycroft / English Springer Spaniel (Canis familiaris) sitting on beach

Mark Raycroft / Bloodhound (Canis familiaris) licking his chops

Mark Raycroft / Bloodhound (Canis familiaris) sitting beside barn

Mark Raycroft / Standard Schnauzer (Canis familiaris) portrait with natural ears

Mark Raycroft / Standard Schnauzer (Canis familiaris) portrait

Mark Raycroft / Great Dane (Canis familiaris) portrait

Mark Raycroft / Siberian Husky (Canis familiaris) adult portrait

Mark Raycroft / Yellow Labrador Retriever (Canis familiaris) adult portrait

Mark Raycroft / Weimaraner (Canis familiaris) sitting in flowers with curious look

Mark Raycroft / Weimaraner (Canis familiaris) portrait in front of tall grass

Mark Raycroft / Weimaraner (Canis familiaris) with open mouth

Mark Raycroft / Weimaraner (Canis familiaris) panting

Mark Moffett / Golden Lion Tamarin (Leontopithecus rosalia) portrait in a tree with a radio collar on its neck, Atlantic Forest, Ilheus, Bahia, Brazil

Sebastian Kennerknecht / African Lion (Panthera leo) eight year old female, Kafue National Park, Zambia

Jaymi Heimbuch / Coyote (Canis latrans) biologist, Marcus Mueller, fitting radio tracking collar to sedated coyote in nature preserve near University of Wisconsin-Madison, Madison, Wisconsin

Pete Oxford / African Elephant (Loxodonta africana) after being fitted with GPS tracking collar, Marakele National Park, Limpopo, South Africa

Mark Raycroft / Standard Schnauzer (Canis familiaris) with autumn leaves

Mark Raycroft / German Shepherd (Canis familiaris)

Mark Raycroft / Boxer (Canis familiaris)

Kristel Richard / Male Riders in traditional costume talking as they ride horses, Feira da Golega, Ribatejo, Portugal.

Yves Lanceau / Domestic dog, English Pointer, head portrait with handler, France

Eric Baccega / Head portrait of a Kayan Lahwi woman with brass neck coils and traditional clothing. The Long Neck Kayan (also called Padaung in Burmese) are a sub-group of the Karen ethnic people from Burma. They we...

Lynn M. Stone / Akita, head portrait, in snow, Connecticut, USA. March.