Marie Read / Western Grebe (Aechmorphus occidentalis), pair during 'rushing' courtship display in which they run across water's surface in synchrony, near Escondido, California, USA, January.

Mark Raycroft / White-tailed Deer (Odocoileus virginianus) buck running, North America

Tony Wu / Humpback whales (Megaptera novaeangliae) male during a competetive heat run. Vava'u, Tonga, South Pacific.

Steve Gettle / Western Grebe (Aechmophorus occidentalis) pair in courtship dance, North Dakota

Mark Raycroft / English Bulldog (Canis familiaris) female running

Tony Wu / Humpback whales (Megaptera novaeangliae) in a heat run, with six males competing for the attention of a female that already has a calf. Vava'u, Kingdom of Tonga

Tony Wu / Humpback whale (Megaptera novaeangliae) and her calf pursued by males during heat run. Vava'u, Tonga, Pacific Ocean.

Tony Wu / Humpback whale (Megaptera novaeangliae) female with calf, pursued by males during heat run. Vava'u, Kingdom of Tonga. Pacific Ocean.

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Roland Seitre / Svalbard Reindeer (Rangifer tarandus platyrhynchus) male and females running, Spitsbergen, Svalbard, Norway

Donald M. Jones / Rocky Mountain Elk (Cervus canadensis nelsoni) bull running, North America

Anup Shah / Cheetah (Acinonyx jubatus) chasing Impala (Aepyceros melampus) female, Masai Mara, Kenya

Sean Crane / Lechwe (Kobus leche) running through water, Okavango Delta, Botswana

Vincent Grafhorst / Hippopotamus (Hippopotamus amphibius) bull charging in territorial display, Botswana

Vincent Grafhorst / Hippopotamus (Hippopotamus amphibius) bull charging in territorial display, Botswana

Jean E. Roche / Bull run, with Camargue bulls leaping over hay bales, Camargue, France, July 2012.

Donald M. Jones / White-tailed Deer (Odocoileus virginianus) buck jumping and flashing tail, North America

Georgette Douwma / Cockerel (Gallus gallus domesticus) crowing in hen run, UK

Donald M. Jones / Pronghorn Antelope (Antilocapra americana) buck runningon the prairie, eastern Montana

Suzi Eszterhas / Cheetah (Acinonyx jubatus) chasing male Thomson's Gazelle (Eudorcas thomsonii), Masai Mara National Reserve, Kenya

Anup Shah / Male African lion {Panthera leo} trotting across his territory to see of an intruder, Masai Mara GR, Kenya. Lions can run at speeds of 50mph!

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) bachelor stallions running together in winter, Wyoming

Michio Hoshino / Alaska Moose (Alces alces gigas) bull charging, Alaska

Mitsuaki Iwago / Ostrich (Struthio camelus) male and two females running, Serengeti National Park, Tanzania

Richard Du Toit / Male Impala running in Kruger National Park, South Africa. Impala can run at speeds of 50mph!

Tony Heald / Two male Ostriches running during dispute, Etosha NP, Namibia. Ostrich can run at speeds of 43mph - they are the fastest terrestrial birds.

Terry Whittaker / Pine marten (Martes martes), adult male killed on road. Black Isle, Scotland, UK. June 2017.

Willi Rolfes/ BIA / Alpine Ibex (Capra ibex) male running, Hohe Tauern National Park, Austria

Donald M. Jones / Pronghorn Antelope (Antilocapra americana) buck running, Montana

SCOTLAND: The Big Picture / Red deer (Cervus elaphus) stag, dead on side of A9 road. Pass of Drumochter, Highlands, Scotland, UK.

SCOTLAND: The Big Picture / Red deer (Cervus elaphus) stag, dead on side of A9 road. Pass of Drumochter, Highlands, Scotland, UK.

Chase Dekker / Red Fox (Vulpes vulpes) father and kit running, Washington

Neil Aldridge / Woman checking over badly injured male Red fox (Vulpes vulpes) which was found after being hit by a vehicle. Fox Project, Kent, England, UK, August. Winner of the Portfolio Category of Nature Photogra...

Alan Murphy/ BIA / Common Merganser (Mergus merganser) male taking flight, Alaska

Sebastian Kennerknecht / Fishing Cat (Prionailurus viverrinus) male running over bridge in urban wetland at night, Diyasaru Park, Colombo, Sri Lanka

Tony Wu / Humpback whale (Megaptera novaeangliae) heat run with seven males, male blowing bubbles, likely a display of dominance. Vava'u, Tonga. Pacific Ocean.

Tony Wu / Humpback whale (Megaptera novaeangliae) male blowing bubbles, likely a display of dominance during heat run. The male had a small portion of his penis protruding. Vava'u, Tonga. Pacific Ocean.

Mark Raycroft / White-tailed Deer (Odocoileus virginianus) buck running, North America

Mark Raycroft / White-tailed Deer (Odocoileus virginianus) buck running, North America

Mark Raycroft / White-tailed Deer (Odocoileus virginianus) buck running, North America

Mark Raycroft / Alaskan Malamute (Canis familiaris) male running, North America

Mark Raycroft / Alaskan Malamute (Canis familiaris) male running, North America

Willi Rolfes/ BIA / Red Deer (Cervus elaphus) stag running, Denmark

Juergen & Christine Sohns / African Wild Dog (Lycaon pictus) males fighting, Sabi-sands Game Reserve, South Africa

Graeme Guy/ BIA / Topi (Damaliscus lunatus) male running, Masai Mara, Kenya

Jaymi Heimbuch / Domestic Dog (Canis familiaris) named Ranger, a scent detection dog with Conservation Canines, searching for moose scat, Adirondack Mountains, New York

Suzi Eszterhas / African Lion (Panthera leo) pride hunting Cape Buffalo (Syncerus caffer), Sabi-sands Game Reserve, South Africa. Sequence 2 of 6

Murray Cooper / Torrent Duck (Merganetta armata) male entering river, Ecuador

Juergen & Christine Sohns / Chimpanzee (Pan troglodytes) male running, Singapore Zoo, Singapore

Yva Momatiuk & John Eastcott / Ostrich (Struthio camelus) male running, Mountain Zebra National Park, South Africa

Tony Wu / Humpback whale (Megaptera novaeangliae) male lunging whilst coming up to breathe, during heat run, Vava'u, Tonga, South Pacific

Tony Wu / Humpback whale (Megaptera novaeangliae) male lunging whilst coming up to breathe, during heat run, Vava'u, Tonga, South Pacific Note baleen whales have two blowholes, whereas toothed whales only have...

Tony Wu / Humpback whale (Megaptera novangliaea) male escort body blocking another male in pursuit of female, part of competitive group heat run, Vava'u, Tonga, South Pacific

Tony Wu / Humpback whale (Megaptera novaeangliae) male surfacing to take a breath, one of several whales engaged in a heat run, Vava'u, Tonga, South Pacific

Juergen & Christine Sohns / Sumatran Tiger (Panthera tigris sumatrae) male chasing lure, Miami, Florida

Mark Raycroft / Nova Scotia Duck Tolling Retriever (Canis familiaris) male running

Mark Raycroft / Golden Retriever (Canis familiaris) male running

Mark Raycroft / Golden Retriever (Canis familiaris) male running

Mark Raycroft / Miniature Smooth Dachshund (Canis familiaris) running

Mark Raycroft / Australian Cattle Dog (Canis familiaris) male running in snow

Mark Raycroft / White-tailed Deer (Odocoileus virginianus) buck running, North America

Mark Raycroft / White-tailed Deer (Odocoileus virginianus) buck in defensive posture, North America

Mark Raycroft / Elk (Cervus elaphus) bull running, North America

Mark Raycroft / Mule Deer (Odocoileus hemionus) dominant buck chasing challenger, North America

Tony Wu / Humpback whale (Megaptera novaengliae) female swimming away from six males during heat run, Vava'u, Tonga, Pacific Ocean.

Tony Wu / Humpback whales (Megaptera novaeangliae) female with male pursuing during heat run, Vava'u, Tonga, Pacific Ocean.

Tony Wu / Humpback whales (Megaptera novaeangliae) heat run with four males pursuing female. Vava'u, Kingdom of Tonga. Pacific Ocean.

Tony Wu / Humpback whales (Megaptera novaengliae) male close up of his belly, with pectoral fin raised, taken during a heat run. Vava'u, Kingdom of Tonga. Pacific Ocean.

Tony Wu / Humpback whales (Megaptera novaeanglliae) group of males during heat run, with one blowing bubbles, Vava'u, Kingdom of Tonga. Pacific Ocean.

Tony Wu / Humpback whales (Megaptera novaeangliae), female with group of six males following during heat run. Vava'u, Kingdom of Tonga.

Ingo Arndt / Svalbard Reindeer (Rangifer tarandus platyrhynchus) males running in snow, Svalbard, Spitsbergen, Norway

Ingo Arndt / Svalbard Reindeer (Rangifer tarandus platyrhynchus) males running and jumping in snow, Svalbard, Spitsbergen, Norway

Ingo Arndt / Svalbard Reindeer (Rangifer tarandus platyrhynchus) male running in snow, Svalbard, Spitsbergen, Norway

Richard Du Toit / Southern Reedbuck (Redunca arundinum) male running, Rietvlei Nature Reserve, South Africa

Richard Du Toit / Burchell's Zebra (Equus burchellii) stallion chasing rival, Rietvlei Nature Reserve, South Africa

Jeff Foott / Bighorn Sheep (Ovis canadensis) males running after female, Zion National Park, Utah

Ingo Arndt / African Lion (Panthera leo) male chasing female to mate, Masai Mara, Kenya

Doug Wechsler / Pennsylvania ambush bug (Phymata pennsylvanica) mating pair, the female has prey, Hickory Run State Park, Pennsylvania, August.

Donald M. Jones / White-tailed Deer (Odocoileus virginianus) buck running through snow, western Montana

Donald M. Jones / White-tailed Deer (Odocoileus virginianus) buck running, western Montana

Donald M. Jones / Elk (Cervus elaphus) bull running through river, western Canada

Donald M. Jones / Desert Bighorn Sheep (Ovis canadensis nelsoni) ram running, southern Nevada

Donald M. Jones / Bighorn Sheep (Ovis canadensis) rams running, western Canada

Donald M. Jones / Barren-ground Caribou (Rangifer tarandus groenlandicus) bull running, central Alaska

Charlie Summers / Arctic grayling (Thymallus arcticus) male and female swimming side by side during spawning run, North Park, Colorado, USA, June.

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) male running, Simien Mountains National Park, Ethiopia

Roland Seitre / Svalbard Reindeer (Rangifer tarandus platyrhynchus) trio running, Spitsbergen, Svalbard, Norway

Roland Seitre / Svalbard Reindeer (Rangifer tarandus platyrhynchus) male running, Spitsbergen, Svalbard, Norway

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) infant male, one year old, running, Gombe National Park, Tanzania