George Sanker / Ellis River high in White Mountain National Forest. New Hampshire, October 2012.

George Sanker / American Buffalo / Bison (Bison bison) grazing in open plains. Yellowstone National Park, Wyoming, October.

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...

Paul D Stewart / Illustration of 'The Entomologist'. Rare copper print with original hand colouring, drawn by George Spratt, printed by George Madely, and sold individually as part of a series through Charles Tilt's F...

George Sanker / American darter / Anhinga (Anhinga anhinga) with caught fish prey, Everglades National Park, Florida, USA, March

George Sanker / Purple gallinule (Porphyrio martinica) moving across waterlily leaves, Everglades National Park, Florida, USA, April

George Sanker / Purple gallinule (Porphyrio martinica) moving across waterlily covered surface, Everglades National Park, Florida, USA, March

George Sanker / Green heron (Butorides virescens) hunting for fish, camouflaged against tree roots, Everglades National Park, Florida, USA, March

George Sanker / Black bear (Ursus americanus) young cub portrait, Yellowstone National Park, Wyoming, USA

George Sanker / Bison (Bison bison) two males head to head, Yellowstone NP, Wyoming, USA

George Sanker / Black Bear (Ursus americanus) cub balancing on branch in tree, Yellowstone NP, Wyoming, USA

George Sanker / Coyote (Canis latrans) standing on rocks at water's edge, sniffing, Yellowstone NP, Wyoming, USA, October

George Sanker / Grizzly bear (Ursus arctos horribilis) walking through long grass, Yellowstone NP, Wyoming, USA, October

George Sanker / American beaver (Castor canadensis) swimming, Grand Teton NP, Wyoming, USA, October

George Sanker / Least Chipmunk (Tamius minimus) feeding on the seeds of a thistle bush during a snowstorm, Grand Teton NP, Wyoming, USA, October

Alex Mustard / Butter hamlet (Hypoplectrus unicolor) pair spawning at dusk, George Town, Grand Cayman, Cayman Islands, British West Indies, Caribbean Sea.

George Sanker / Grizzly bear (Ursus arctos horribilis) walking, Yellowstone National Park, Wyoming, USA, October

George Sanker / Long-tailed weasel (Mustela frenata) standing on hind legs, Yellowstone National Park, Wyoming, USA, June

George Sanker / Two Least Chipmunks (Tamias minimus) sitting on tree stump feeding, Yellowstone National Park, Wyoming, USA, October, crop of 1373882

George Sanker / Pond in forest, Baxter State Park, Maine, USA, October 2007

George Sanker / Newborn Elk (Cervus canadensis) calf looks up to its mother, Yellowstone National Park, USA, June

George Sanker / Coyote (Canis latrans) climbing over rocks carrying pup in mouth, Yellowstone National Park, Wyoming, USA, June

George Sanker / Moose (Alces alces) jumping a fence, Grand Teton National Park, Wyoming, USA, October

George Sanker / Oxbow Bend of the Snake River with the Grand Tetons on the horizon, Grand Teton National Park, Wyoming, USA, September 2006

George Sanker / Black bear (ursus americanus) cub standing on hind legs, Yellowstone National Park, USA, June

George Sanker / Baby Black Bear (Ursus americanus) up a tree, Yellowstone National Park, USA, May

George Sanker / Portrait of Grey Wolf (Canis lupus). Yellowstone National Park, Wyoming, USA, October.

George Sanker / Portrait of Golden Mantled Ground Squirrel (Spermophilus lateralis) with a blade of grass in its mouth. Yellowstone National Park, Wyoming, USA, May.

George Sanker / Portrait of a Grizzly Bear (Ursus arctos horribilis) against rock. Yellowstone National Park, Wyoming, USA, May.

George Sanker / Elk / Wapiti (Cervus canadensis) herd with young on meadowland against the Grand Tetons, low clouds and the Snake River. Grand Teton National Park, Wyoming, USA, June.

George Sanker / Lesser Scaup (Aythya affinis) female walking across ice. Yellowstone National Park, Wyoming, USA, June.

George Sanker / Moose (Alces alces) bull male walking through frosty grass. Grand Teton National Park, Wyoming, USA, October.

George Sanker / Limber Pine (Pinus flexilis). Grand Teton National Park, Wyoming, USA, October 2010. Famous patriarch tree of the Grand Tetons just after fall snowstorm. Winner: World Landscapes category in the Outdo...

George Sanker / Limber Pine (Pinus flexilis) against high mountain peaks. Grand Teton National Park, Wyoming, USA. Autumn 2010.

George Sanker / Yellow-bellied Marmots (Marmota flaviventris) mating. Yellowstone National Park, Wyoming, USA, June.

George Sanker / African lion (Panthera leo) pair, Masai Mara National Reserve, Kenya, January

George Sanker / Moose (Alces alces) bull walking through woods during a snowstorm, Grand Teton National Park, Wyoming, USA, October

George Sanker / Black bear (Ursus americanus) cub, cinnamon phase, climbing fir tree, Yellowstone National Park, Wyoming, USA, June

George Sanker / African lion (Panthera leo) male and female at sunrise, Masai Mara National Reserve, Kenya, January

George Sanker / Black bear (Ursus americanus) cubs, male and female, one black the other brown, playing roughly, Yellowstone National Park, Wyoming, USA, May

George Sanker / Male African lion (Panthera leo) lying in grass at sunrise, Masai Mara National Reserve, Kenya, January

George Sanker / Male North American red squirrel (Tamiasciurus hudsonicus) alarm calling, Yellowstone National Park, Wyoming, USA, June

George Sanker / Black bear (Ursus americanus) cub, brown phase, looking out from behind tree trunk, Yellowstone National Park, Wyoming, USA, May

George Sanker / Moose (Alces alces) bull shaking off water at sunset, Great North Woods, Baxter State Park, Maine, New England, USA, Autumn

George Sanker / Young Black bear (Ursus americanus) cub climbing mature fir tree, Yellowstone National Park, Wyoming, USA, May

MORLEY READ / "Lonesome George", the last Galapagos Tortoise {Geochelone elephantopus} from Pinta Island, Galapagos

Jack Dykinga / Ponderosa pines {Pinus ponderosa}, Promontory Butte on General George Crook Trail along the Mogollon Rim, Apache Sitgreaves National Forest, Arizona, USA

George McCarthy / Grey squirrel feeding on apple {Sciurus carolinensis} Sussex, UK.

George McCarthy / Persian squirrel {Sciurus anomalus} alert on tree branch, Greece.

George McCarthy / Spur thighed tortoise portrait {Testudo graeca} Island of Lesbos, Greece

George McCarthy / Silver spotted skipper butterfly, Surrey, England

George McCarthy / Hibernating dormouse {Muscardinus avellanarius} curled up asleep in nest, Sussex, UK

Yva Momatiuk & John Eastcott / Arctic Fox (Alopex lagopus) pup inspects tundra near family's den, St George Island, The Pribilof Islands, Alaska

Yva Momatiuk & John Eastcott / Arctic Fox (Alopex lagopus) pup in blue phase at entrance of burrow, Saint Paul Island, Pribilof Islands, Alaska

Tui De Roy / Pinta Island Galapagos Tortoise (Chelonoidis nigra abingdoni), Lonesome George, the last survivor of his race, Darwin Reserve Station, Santa Cruz Island, Galapagos Islands, Ecuador

Hanne & Jens Eriksen / Damage caused by Hurricane George. Key West, Florida, USA

George McCarthy / Grass snake {Natrix natrix} threatening Common toad {Bufo bufo} puffed up in defence, UK

George McCarthy / Bittern (Botaurus stellaris) standing in grass. Lesvos, Greece, Europe

George McCarthy / Grass snake {Natrix natrix} with Common toad {Bufo bufo} inflated in defense. UK

George McCarthy / Canada geese family on water {Branta canadensis} Sussex UK

George McCarthy / Common frog {Rana temporaria} on heart-shaped lily pad, England, UK

George Sanker / American Purple Gallinule (Porphyrio martinica) displaying brightly coloured wings. Everglades National Park, Florida, USA, March.

George Sanker / Greater Yellowlegs (Tringa melanoleuca) in shallow water. Everglades National Park, Florida, USA, March.

George Sanker / Green Heron (Butorides virescens) in wetlands. Everglades National Park, Florida, USA, March.

George Sanker / Coastal rocks and calm sea. Acadia National Park, Maine, Atlantic Coast, November 2012.

George Sanker / Coast of Acadia National Park, Maine during Hurricane Sandy. October, 2012.

George Sanker / Acadia National Park, Maine. The Atlantic Ocean. Post-Hurricane Sandy, October.

George Sanker / Acadia National Park, Maine. The Atlantic Ocean. Hurricane Sandy, October.

George Sanker / Storm surge waves breaking on coastal rocks, with person seen through the sea spray. Acadia National Park, Maine. The Atlantic Ocean, Hurricane Sandy, October 2012.

George Sanker / Trees reflected in misty pond. Grassy Pond. Baxter State Park, Maine, October, 2012.

George Sanker / Abstract of ice on water. Baxter State Park, Maine, USA, October 2012.

George Sanker / Rock in shallows of a bay. Acadia National Park, Maine, October, 2012.

George Sanker / Coastal rocks. Acadia National Park, Maine, October, 2012.

George Sanker / Rock, trees and leaves. Ellis River, White Mountain National Forest, New Hampshire, October, 2012.

George Sanker / Red Maple Tree (Acer rubrum) in autumn colours. Baxter State Park, Maine, September.

George Sanker / Pronghorn (Antilocapra americana) in landscape. Yellowstone National Park, October.

George Sanker / Birch trees (Betulus) in landscape. Yellowstone National Park, Wyoming, October 2011.

George Sanker / American Red Squirrel (Tamiasciurus hudsonicus). Grand Teton National Park, Wyoming, October.

George Sanker / Grizzly Bear (Ursus arctos horribilis) before dramatic mountain. Grand Teton National Park, Wyoming, USA, June.

George Sanker / Grizzly Bear (Ursus arctos horribilis) mother and cubs. Grand Teton National Park, Wyoming, USA, June.

George Sanker / Grizzly Bear (Ursus arctos horribilis) cubs following their mother. Grand Teton National Park, Wyoming, USA, June.

George Sanker / Elk or Wapiti (Cervus canadensis) calf grooming by river. Grand Teton National Park, Wyoming, USA, June.

George Sanker / Elk / Wapiti (Cervus canadensis) resting by water, calf waiting for mother. Grand Teton National Park, Wyoming, USA, June.

George Sanker / Moose (Alces alces) mother and calf. Grand Teton National Park, Wyoming, USA, June.

George Sanker / American Red Fox (Vulpes vulpes) female stalking. Grand Teton National Park, Wyoming, USA, June.

George Sanker / American Red Fox (Vulpes vulpes) with Uinta ground squirrel (Urocitellus armatus) prey. Grand Teton National Park, Wyoming, USA, June.

George Sanker / American Red Fox (Vulpes vulpes) with Uinta ground squirrel (Urocitellus armatus) prey. Grand Teton National Park, Wyoming, USA, June.

George Sanker / American Red Fox (Vulpes vulpes) stalking. Grand Teton National Park, Wyoming, June.

George Sanker / American Red Fox (Vulpes vulpes) stalking. Grand Teton National Park, Wyoming, June.

George Sanker / American Red Fox (Vulpes vulpes) cubs playing. Grand Teton National Park, Wyoming, June.

George Sanker / American Red Fox (Vulpes vulpes) cubs playing. Grand Teton National Park, Wyoming, June.

George Sanker / American Red Fox (Vulpes vulpes) cubs playing with its mother. Grand Teton National Park, USA, June.

George Sanker / American Red Fox (Vulpes vulpes). Grand Teton National Park, Wyoming, June.

George Sanker / Grizzly Bear (Ursus arctos horribilis) in sage brush above meadow and trees. Grand Teton National Park, June.

George Sanker / Coyote (Canis latrans) with Elk (Cervus canadensis) calf prey. Yellowstone National Park, Wyoming, June.