Jim Brandenburg / Arctic Wolf (Canis lupus) pack on ice field, Ellesmere Island, Nunavut, Canada

Jim Brandenburg / Timber Wolf (Canis lupus) pack at White-tailed Deer (Odocoileus virginianus) kill, Minnesota

Jim Brandenburg / Timber Wolf (Canis lupus) pack feeding on White-tailed Deer (Odocoileus virginianus) carcass, Minnesota

Jim Brandenburg / Timber Wolf (Canis lupus) pack along water's edge, Moose Lake, Boundary Waters Canoe Area Wilderness, Minnesota

Tony Heald / African wild dogs hunting {Lycaon pictus} Mana Pools NP Zimbabwe, Africa

Juergen Freund / Harp Seal (Pagophilus groenlandica) juvenile under pack ice. Magdalen Islands, Canada

Jabruson / African wild dog pack {Lycaon pictus} attack Wildebeest {Connochaetus taurinus} Serengeti NP, Tanzania

Jeff Rotman / Whitetip reef shark pack hunting at night {Triaenodon obesus} Cocos Is, Costa Rica, Pacific Ocean

Andy Rouse / Polar bear (Ursus maritimus) on pack ice, Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) on pack ice, Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) on pack ice, Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) on pack ice, Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) on pack ice, Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) on pack ice, Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) on iceberg, Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) walking on pack ice sniffing the air, Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) on pack ice Svalbard, Norway. October

Andy Rouse / Polar Bear (Ursus maritimus) on pack ice Svalbard, Norway. October

Andy Rouse / Polar bear (Ursus maritimus) on pack ice, Svalbard, Norway. October

Andy Rouse / Polar bear (Ursus maritimus) mother and yearling cub on pack ice at sunset, Svalbard, Norway. August.

Andy Rouse / Polar Bear (Ursus maritimus) on pack ice, Svalbard, Norway. October

Juergen & Christine Sohns / African Wild Dog (Lycaon pictus) group surrounding Cape Warthog (Phacochoerus aethiopicus), Tswalu Game Reserve, South Africa

Juergen & Christine Sohns / African Wild Dog (Lycaon pictus) group attacking Cape Warthog (Phacochoerus aethiopicus), Tswalu Game Reserve, South Africa

Andy Rouse / Polar bear (Ursus maritimus) standing on pack ice at sunset. Svalbard, Norway.

Andy Rouse / Polar bear (Ursus maritimus) standing on pack ice. Svalbard, Norway. August 2018.

Andy Rouse / Polar Bear (Ursus maritimus) standing on pack ice, looking up at ship, Svalbard, Norway. August.

Andy Rouse / Polar bear (Ursus maritimus) standing on pack ice. Svalbard, Norway.

Andy Rouse / Pack ice, Svalbard, Arctic

Staffan Widstrand / African Wild Dog / Painted Dog pack (Lycaon pictus) eating carcass, Zimanga Private Nature Reserve, KwaZulu Natal, South Africa

John Shaw / Polar bear (Ursus maritimus) female with her cub, in the pack ice. Spitsbergen, Svalbard, Norway. July.

John Shaw / Polar bear (Ursus maritimus) female with her cub, in the pack ice. Spitsbergen, Svalbard, Norway. July.

Sven Zacek / Walrus (Odobenus rosmarus) colony in front of glacier, Magdalenefjorden fjord, Spitsbergen, Norway. June 2014.

Jaymi Heimbuch / Domestic Dog (Canis familiaris) named Dio, a scent detection dog with Conservation Canines, smelling scent, Pack Forest, Eatonville, Washington

David Allemand / Polar bear (Ursus maritimus) moving around on ice floe, looking for food, Svalbard, Norway, July.

Karine Aigner / African wild dog (lycaon pictus) watching as two of the pack's pups play. Malilangwe Wildlife Reserve, Zimbabwe.

Karine Aigner / African wild dog (lycaon pictus) pups playing Malilangwe Wildlife Reserve, Zimbabwe.

Karine Aigner / African wild dog (lycaon pictus) carries a pup from its pack. Malilangwe Wildlife Reserve, Zimbabwe.

Karine Aigner / African wild dog (Lycaon Pictus) pups wait for the rest of the pack to lead the way. Mana Pools, Zimbabwe.

Karine Aigner / Portrait of a young African wild dog (Lycaon pictus) amongst its pack. Zimbabwe.

Karine Aigner / African wild dogs (Lycaon pictus) of the same pack playing and greeting each other. Zimbabwe

Karine Aigner / African wild dogs (Lycaon Pictus) pack killing a newborn Cape buffalo (Syncerus caffer) calf, Zimbabwe.

Karine Aigner / Pack of African wild dogs (Lycaon Pictus) attacking newborn Cape buffalo (Syncerus caffer) calf near its mother. Zimbabwe.

Karine Aigner / African wild dog (Lycaon Pictus) chasing a pack member to steal it's prey. Zimbabwe.

Karine Aigner / African wild dog pups (Lycaon Pictus) looking at the camera. Zimbabwe.

Karine Aigner / African wild dog (Lycaon Pictus) pups at dusk and looking around for the adults. Mana Pools, Zimbabwe.

Karine Aigner / Cheetah (Acinonyx jubatus) trying to fight off a pack of African wild dogs (Lycaon Pictus) from stealing Impala prey in Linyanti Wildlife Reserve, Botswana.

Karine Aigner / Blue wildebeest (Connochaetes taurinus) huddled together in a circle, protecting each other from a pack of four African wild dogs (Lycaon Pictus). Botswana.

Karine Aigner / African wild dogs (lycaon pictus) fighting with a Spotted hyena (Crocuta crocuta) Malilangwe Wildlife Reserve. Zimbabwe.

Karine Aigner / African wild dogs (Lycaon pictus) five attack a Cheetah (Acinonyx jubatus) defending its Impala kill. Linyanti Wildlife Reserve, Botswana.

Karine Aigner / African wild dogs (Lycaon pictus) watching an African elephant (Loxodonta africana) bathe in mud. Zimbabwe.

Karine Aigner / African wild dog (lycaon pictus) plays with one of the pack's pups. Malilangwe Wildlife Reserve, Zimbabwe.

Karine Aigner / African wild dog (lycaon pictus) lactating alpha female, begging one of the pack members that has returned from the hunt, to regurgitate for her. Malilangwe Wildlife Reserve, Zimbabwe.

Tony Heald / Snow Petrel (Pagodroma nivea), four resting on floating ice. Near Twitcher Glacier, South Georgia. October 2017.

Tony Heald / Leopard seal (Hydrurga leptonyx) resting on ice floe near Twitcher Glacier, South Georgia. October.

Sue Flood / Emperor penguin (Aptenodytes forsteri) moulting chicks on ice floe, Ross Sea, Antarctica. The immature birds make their way across the fast ice and assemble in huge numbers on the ice edge waiting to...

Jeff Foott / African wild dog (Lycaon pictus) pack passing b ywaterhole while hunting, Chobe National Park, Botswana.

Jeff Foott / African wild dog (Lycaon pictus) pack passing waterhole while hunting, Chobe National Park, Botswana.

Robin Chittenden / Street dogs (Canis familiaris) pack, Romania. May 2018.

Sylvain Cordier / Polar bear (Ursus maritimus) female with juvenile, age one year and a half, Wrangel Island, Russia.

Sylvain Cordier / Polar bear (Ursus maritimus) female with young, age one year and a half, resting on the ice, Wrangel island, Far East Russia.

Sylvain Cordier / Polar bear (Ursus maritimus) adult female with cub, one year and a half old, Wrangel island, Far East Russia.

Sylvain Cordier / Polar bear (Ursus maritimus) adult female with young age one year and a half. Wrangel island, Far East Russia.

Sebastian Kennerknecht / Coyote (Canis latrans) pack in territorial howl in winter, Lamar Valley, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / Coyote (Canis latrans) pack in territorial howl in winter, Lamar Valley, Yellowstone National Park, Wyoming

Andy Rouse / Polar bear (Ursus maritimus) standing at the edge of the pack ice, Svalbard, Norway. June.

Andy Rouse / Polar bear (Ursus maritimus) walking on pack ice, Svalbard, Norway. September.

Andy Rouse / Polar bear (Ursus maritimus) on the edge of the pack ice, Svalbard, Norway. June.

Andy Rouse / Polar bear (Ursus maritimus) standing on the edge of the pack ice, Svalbard, Norway. June.

Andy Rouse / Adelie Penguin (Pygoscelis adeliae) on ice, Antarctic Sound, Antarctica.

Andy Rouse / Adelie Penguin (Pygoscelis adeliae) on ice, Antarctic Sound, Antarctica.

Andy Rouse / Adelie Penguin (Pygoscelis adeliae) on ice, Antarctic Sound, Antarctica.

Andy Rouse / Gentoo Penguin (Pygoscelis papua) jumping off ice Antarctica

Emanuele Biggi / Cave centipede (Thereuopoda longicornis) with sperm pack transferred by a male, Gomantong caves, Borneo, Sabah, Malaysia.

Bruno D'Amicis / Pack of Wild Apennine wolves (Canis lupus italicus) patrolling their mountain territory in autumn. Central Apennines, Abruzzo, Italy. September. Italian endemic subspecies.

Bruno D'Amicis / Apennine / Italian wolf (Canis lupus italicus) pack of three walking on mountain slope in snow. Abruzzo, Central Apennines, Italy. Feb 2012

Bruno D'Amicis / Apennine / Italian wolf (Canis lupus italicus) pack of three walking on mountain slope. Abruzzo, Central Apennines, Italy

Bruno D'Amicis / Wild Apennine wolf (Canis lupus italicus) pack of four sleeping during day at forest edge. Central Apennines, Abruzzo, Italy. March Italian endemic subspecies.

Bruno D'Amicis / Wild Apennine wolf (Canis lupus italicus) pack of four sleeping during day at forest edge. Central Apennines, Abruzzo, Italy. March. Italian endemic subspecies.

Michel Roggo / Adelie penguin (Pygoscelis adeliae) on ice floe, Amundsen Sea, Antarctica. Photographed for The Freshwater Project

Philippe Clement / Grey wolf (Canis lupus) pack stepping over a fallen tree trunk in the snow, Bavarian Forest National Park, Germany, March. Captive.

Ingo Arndt / Walrus (Odobenus rosmarus) hauled out on ice floe, Spitsbergen, Svalbard, Norway, April..

Sean Viljoen / Pack of African wild dogs (Lycaon pictus) feeding, Khwai River, Moremi Game Reserve, Botswana.

Sean Viljoen / Pack of African wild dogs (Lycaon pictus) feeding, Khwai River, Moremi Game Reserve, Botswana.

Steven Kazlowski / Polar bear (Ursus maritimus) young bear playing with a piece of whale baleen on newly formed pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) mother with juveniles resting on newly formed pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) motherwith juvenile resting on newly formed pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) profile of a young female walking over newly formed pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) young bear trying to pound a hole in the newly forming pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) young bear trying to pound a hole in the newly forming pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) young bear trying to pound a hole in the newly forming pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) sow with juvenile rest on newly formed pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) two young adults play fighting on newly formed pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) two young adults play fighting on newly formed pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) young bear covering eyes with paw, on newly formed pack ice, during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska

Steven Kazlowski / Polar bear (Ursus maritimus) sow with two juveniles resting on newly formed pack ice during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska