Diane McAllister / Polar bears (Ursus maritimus) fighting in water. Beaufort Sea , Kaktovik, Alaska, USA. Highly commended in the Polar Passion category of the Nature's Best Photography Competition 2019.

John Cancalosi / Snapping turtle (Chelydra serpentina) and Bluegill (Lepomis macrochirus) fish attempting to feed on algae on turtle's shell. Maryland, USA. August.

John Cancalosi / Timber rattlesnake (Crotalus horridus) females coiled up in leaf litter, newborn young sheltering under rock. At maternity site, Pennsylvania, USA. August.

John Cancalosi / Timber rattlesnake (Crotalus horridus) females in undergrowth at maternity site, Pennsylvania, USA. August.

John Cancalosi / House finch (Haemorhous mexicanus), two females on Sotol (Dasylirion wheeleri). Sonoran desert, Arizona, USA. July.

John Cancalosi / Timber rattlesnake (Crotalus horridus) females and newborn young at maternity site. Pennsylvania, USA. August.

John Cancalosi / Slimy salamander (Plethodon glutinosus) on leaves in pool of water. Pennsylvania, USA. May.

John Cancalosi / Amish man mowing hay with three horses. Lancaster County, Pennsylvania, USA. June 2019.

John Cancalosi / Amish man rowing hay with horse-drawn equpment. Lancaster County, Pennsylvania, USA. June 2019.

John Cancalosi / Sonoran desert toad (Incilius alvarius) pair mating, trail of toad spawn in water. Sonoran desert, Arizona, USA. August.

John Cancalosi / Sonoran desert toad (Incilius alvarius) pair in amplexu, trail of toad spawn in water. Sonoran desert, Arizona, USA. August.

John Cancalosi / Colorado river toad (Incilius alvarius) pair mating. Sonoran desert, Arizona, USA. August.

John Cancalosi / Colorado river toad (Incilius alvarius) male calling to attract females, vocal sac filled with air. Sonoran desert, Arizona, USA. August.

John Cancalosi / White-winged dove (Zenaida asiatica) vocalising, perched on Sotol (Dasylirion wheeleri). Sonoran desert , Arizona, USA. July.

Oscar Dewhurst / Mountain bluebird (Sialia currucoides). Yellowstone National Park, Wyoming, USA. September.

Oscar Dewhurst / Moose (Alces alces) bull, portrait. Grand Teton National Park, Wyoming, USA. September.

Oscar Dewhurst / Moose (Alces alces) bull swimming across river. Grand Teton National Park, Wyoming, USA. September.

Oscar Dewhurst / Moose (Alces alces) bull wading in river. Grand Teton National Park, Wyoming, USA. September.

Oscar Dewhurst / Trumpeter swan (Cygnus buccinator) pair on bank. Grand Teton National Park, Wyoming, USA. September.

Oscar Dewhurst / Steller's jay (Cyanocitta stelleri) perched on branch. Grand Teton National Park, Wyoming, USA. September.

Oscar Dewhurst / Clark's nutcracker (Nucifraga columbiana) feeding on Pine (Pinus sp) seeds. Grand Teton National Park, Wyoming, USA. September.

Oscar Dewhurst / Killdeer (Charadrius vociferus) stretching wings. Yellowstone National Park, Wyoming, USA. September.

Hanne & Jens Eriksen / Black-billed magpie (Pica hudsonia) in flight. Colorado, USA, August.

Hanne & Jens Eriksen / American bison (Bison bison) herd grazing on hillside, South Dakota, USA, September 2017.

Hanne & Jens Eriksen / Least chipmunk (Tamias minimus) gathering plant material, South Dakota, USA, September.

Claudio Contreras / Catalina Desert Iguana (Dipsosaurus catalinensis), Catalana (Santa Catalina) Island, Loreto Bay National Park, Gulf of California (Sea of Cortez), Baja California, Mexico, May, Second place in Visions...

Charlie Summers / American badger (Taxidea taxus) rolling on the side of the mound that marks the entrance to its burrow. North Park, Colorado, USA, June.

Charlie Summers / American badger (Taxidea taxus) crossing a major South Dakota highway with a Black-tailed Prairie Dog (Cynomys ludovicianus) firmly in its grasp. This is a female, a nursing mother, that was returning...

Charlie Summers / Wyoming ground squirrel (Urocitellus elegans), standing alert. Arapaho National Wildlife Refuge, Colorado, USA, June.

Charlie Summers / Meteor going past comet 46P / Wirtanen and the Pleiades seen in early morning hours, Echo Lake, Colorado, USA. September 17 2018.

Charlie Summers / Wyoming ground squirrel (Urocitellus elegans) standing to have a better look around. North Park, Arapaho Wildlife Refuge, Colorado, USA.

Charlie Summers / Wyoming ground squirrel (Urocitellus elegans), foraging for food in tall grass covered with dew. Arapaho National Wildlife Refuge, Colorado, USA, June.

Charlie Summers / White-tailed prairie dog (Cynomys leucurus) youngsters playing on top of burrow, Arapaho National Wildlife Refuge of North Park, Colorado.

Charlie Summers / Ruddy duck (Oxyura jamaicensis) female rolling on her side as she preens. Image taken on an Arapaho National Wildlife Refuge pond in North Park, Colorado.

Charlie Summers / Ruddy duck (Oxyura jamaicensis) drake making bubbles in courtship behaviour, Arapaho National Wildlife Refuge pond, North Park, Colorado.

Charlie Summers / Rock squirrel (Otospermophilus variegatus) on the rim of the Grand Canyon, Arizona, USA, September.

Charlie Summers / Rock Squirrel (Otospermophilus variegatus) climbing on a lichen covered rock, Grand Canyon, Arizona, USA.

Charlie Summers / American Pika (Ochotona princeps) leaping from one alpine rock to another as it heads to its home carrying food for the winter months. Rocky Mountain National Park, Colorado, USA. August.

Charlie Summers / Pied-billed grebe (Podilymbus podiceps) feeding a Fathead Minnow (Pimephales promelas) to one of its chicks. Arapaho National Wildlife Refuge, Colorado, USA, June.

Charlie Summers / Pied-billed Grebe (Podilymbus podiceps) feeding minnow to colorful chick. Arapaho Wildlife Refuge, North Park, Colorado, USA, July.

Charlie Summers / Black-tailed Prairie Dog (Cynomys ludovicianus) mother carrying one of her young to their burrow. Cherry Creek State Park, Colorado, USA, May.

Charlie Summers / Arctic grayling (Thymallus arcticus) male gaping at the approach of another male in the background. North Park, Colorado, USA. June.

Charlie Summers / Eared grebes (Podiceps nigricollis) courtship dance on lake, Arapaho National Wildlife Refuge, North Park, Colorado, USA, June.

Charlie Summers / Eared grebes (Podiceps nigricollis) stand erect in water during courtship, North Park, Colorado, USA. June.

Charlie Summers / Eared grebes (Podiceps nigricollis) stand erect on water, din courtship behaviour, North Park, Colorado, USA. June.

Charlie Summers / Widefield view of the comet 46P / Wirtanen buzzing past the Pleiades during the early morning hours. Echo Lake, Colorado, USA. September 17, 2018.

Charlie Summers / White-tailed prairie dog (Cynomys leucurus) bounding through dew covered prairie grass, North Park, Colorado, USA.

Charlie Summers / Black-tailed prairie dogs (Cynomys ludovicianus) youngsters stay close together above their burrow, Cherry Creek State Park of Colorado, USA, May.

Charlie Summers / American badger (Taxidea taxus) female with Black-tailed Prairie Dog (Cynomys ludovicianus) prey she is taking to her cubs in their burrow. Custer State Park, South Dakota, USA. July.

Charlie Summers / American badger (Taxidea taxus) female with Black-tailed Prairie Dog (Cynomys ludovicianus) prey she is taking to her cubs in their burrow. Custer State Park, South Dakota, USA. July.

John Shaw / Desert bighorn sheep ram (Ovis canadensis nelsoni) rubbing against a creosote bush (Larrea tridentata). Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep ram (Ovis canadensis nelsoni) descends a steep sandsone wall. Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep ram (Ovis canadensis nelsoni) descends a steep sandsone wall. Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep ram (Ovis canadensis nelsoni) descends a steep sandsone wall. Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep (Ovis canadensis nelsoni) rams on steep sandstone wall. Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep (Ovis canadensis nelsoni) rams on steep sandstone wall. Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep (Ovis canadensis nelsoni) ram steep sandstone wall. Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep (Ovis canadensis nelsoni) rams on steep sandstone wall. Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep ram (Ovis canadensis nelsoni) on sandsone wall. Valley of Fire State Park, Nevada, USA. February.

John Shaw / Desert bighorn sheep ram (Ovis canadensis nelsoni). Scars on face from fighting other males. Valley of Fire State Park, Nevada, USA. February.

John Abbott / Western pygmy blue (Brephidium exilis) butterfly. Mono County, California, USA. June.

George Sanker / Pileated woodpecker (Dryocopus pileatus) feeding, on tree trunk. Acadia National Park, Maine, USA. February.

George Sanker / Pileated woodpecker (Dryocopus pileatus) feeding, on tree trunk. Acadia National Park, Maine, USA. February.

George Sanker / Exposed beach with rock pools at low tide, at dawn. Acadia National Park, Maine, USA. February 2018.

George Sanker / Merlin (Falco columbarius) perched in tree. Acadia National Park; Maine; USA. February.

George Sanker / Merlin (Falco columbarius) perched in tree. Acadia National Park; Maine; USA. February.

George Sanker / White-tailed deer (Odocoileus virginianus), doe and fawns feeding in a row on snow covered pond, rear view. Acadia National Park, Maine, USA. January.

George Sanker / White-tailed deer (Odocoileus virginianus) doe and fawn standing amongst Bulrushes on snow covered pond. Acadia National Park, Maine, USA. January.

George Sanker / White-tailed deer (Odocoileus virginianus) doe and fawn standing on snow covered pond. Acadia National Park, Maine, USA. January.

George Sanker / White-tailed deer (Odocoileus virginianus) fawn standing in snow. Acadia National Park, Maine, USA. January.

George Sanker / White-tailed deer (Odocoileus virginianus) fawn on snow covered pond. Acadia National Park, Maine, USA. January.

George Sanker / White-tailed deer (Odocoileus virginianus) fawn standing beside Bulrushes (Typha sp) on snow-covered pond. Acadia National Park, Maine, USA. December.

George Sanker / White-tailed deer (Odocoileus virginianus) buck standing in snow, portrait. Acadia National Park, Maine, USA. November.

George Sanker / White-tailed deer (Odocoileus virginianus) buck standing in snow. Acadia National Park, Maine, USA. November.

George Sanker / Sunrise over coastal rocks and Atlantic ocean, Acadia National Park, Maine, USA. November 2018.

George Sanker / Sunrise over coastal rocks and Atlantic ocean, Acadia National Park, Maine, USA. November 2018.

George Sanker / Lakeside trees in autumn, cliffs of Champlain Mountain in background. Acadia National Park, Maine, USA. October 2018.

George Sanker / Northern goshawk (Accipiter gentilis) standing on Mallard duck (Anas platyrhynchos) prey. Acadia National Park, Maine, USA. October.

George Sanker / Rocky coastline and Atlantic ocean at dawn, coniferous forest along coast. Acadia National Park, Maine, USA. October 2013.

George Sanker / Rockpool and Seaweed covered rocky shore at dawn. Acadia National Park, Maine, USA. October 2013.

George Sanker / Rocky shore and sea at sunset. Wonderland, Acadia National Park, Maine, USA. October 2013.

George Sanker / White-tailed deer (Odocoileus virginianus) buck standing in grassland. Acadia National Park, Maine, USA. October.

George Sanker / Muskrat (Ondatra zibethicus) feeding in beaver pond. Acadia National Park, Maine. September.

George Sanker / Muskrat (Ondatra zibethicus) sitting, with wet fur, portrait. Acadia National Park, Maine.

George Sanker / White-tailed deer (Odocoileus virginianus) fawn face to face with Wild turkey (Meleagris gallopavo), in woodland clearing. Acadia National Park, Maine, USA. August.

George Sanker / White-tailed deer (Odocoileus virginianus) doe and fawn standing in grassland in light mist. Acadia National Park, Maine, USA. August.

George Sanker / Great blue heron (Ardea herodias) with Eastern newt (Notophthalmus viridescens) in beak. Acadia National Park, Maine, USA.. July.

George Sanker / Common snapping turtle (Chelydra serpentina) swimming below surface in pond. Acadia National Park; Maine; USA. July.

George Sanker / Common snapping turtle (Chelydra serpentina) on bottom of pond, view from above. Acadia National Park; Maine; USA. July.

George Sanker / White-tailed deer (Odocoileus virginianus) doe licking fawn in grassland, at edge of woodland. Acadia National Park, Maine, USA. July.

George Sanker / Common snapping turtle (Chelydra serpentina) at surface, in pond. Acadia National Park, Maine, USA. July.

George Sanker / Razorbill (Alca torda) in flight. Machias Seal Island, Maine, USA / New Brunswick, Canada. July.

George Sanker / Atlantic puffin (Fratercula arctica) landing, wings outstretched. Machias Seal Island, off the coast of Maine, USA. July. This island is disputed between USA and Canada.

George Sanker / White-tailed deer (Odocoileus virginianus) doe and fawn at edge of beaver pond. Acadia National Park, Maine, USA. June.

George Sanker / White-tailed deer (Odocoileus virginianus) doe with suckling fawn at edge of beaver pond. Acadia National Park, Maine, USA. June.

George Sanker / Coniferous forest and mountains reflected in beaver pond at sunrise. Grand Teton National Park, Wyoming, USA. June 2018.