Oscar Dewhurst / Mute swan (Cygnus olor) pair at sunrise. London, UK. December.

Andy Rouse / African lion (Panthera leo) female carrying young cub, Masai Mara, Kenya, Africa. Highly commended in the African Wildlife Category of the Nature's Best Photography Competition 2019.

Markus Varesvuo / Sparrowhawk (Accipiter nisus) adult female, Norway, October.

Will Burrard-Lucas / White rhino (Ceratotherium simum) female and juvenile, Solio Game Reserve, Solio Ranch, Kenya. Taken with remote camera buggy / BeetleCam.

Doug Perrine / Humpback whale (Megaptera novaeangliae) calf riding on mother's head. Near Nomuka Island, Ha'apai Islands, Tonga.

Nick Garbutt / American bison (Bison bison) female covered in hoar frost near hot spring, portrait. Midway Geyser Basin, Yellowstone National Park, USA. February.

Danny Green / Polar bear (Ursus maritimus) female and cubs play fighting. Svalbard, Norway, March 2018.

Danny Green / Polar bear (Ursus maritimus) male female pair looking upwards, snow covered hills in background. Svalbard, Norway, April 2018.

Danny Green / Polar bear (Ursus maritimus) group on ice, female and cubs feeding on Whale carcass. Svalbard, Norway, June 2018.

Danny Green / Polar bear (Ursus maritimus) female resting with cubs on glacier. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) female and cubs feeding on Whale carcass. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and two cubs feeding on Whale carcass. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and cubs, standing on sea ice. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and cubs resting on sea ice. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) female and cubs, one cub walking up slope of ice in foreground. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and cubs feeding on Whale carcass. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and cubs feeding on Whale carcass, on iceberg. Svalbard, Norway, July 2018.

Danny Green / Polar bear (Ursus maritimus), male and female approaching each other across snow covered rocky landscape. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male approaching female on snow covered hill top. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male approaching female in rocky area covered in snow. Svalbard, Norway, April 2019.

Danny Green / RF - Polar bear (Ursus maritimus) female walking across ice. Svalbard, Norway, April. (This image may be licensed either as rights managed or royalty free.)

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

Gabriel Rojo / Guanaco (Lama guanicoe) female and newborn baby, nose to nose in grassland. La Pampa Province, Argentina.

Alex Mustard / Yellowtail tang (Zebrasoma xanthurum) male and female turn belly to belly during spawning to ensure fertilization. Temple, Ras Umm Sid, Sharm El Sheikh, Sinai, Egypt. Red Sea. This action is very fast...

Matthew Maran / Red fox (Vulpes vulpes) dog interacting with a vixen in an urban garden. North London, UK. June.

Matthew Maran / Red fox (Vulpes vulpes) dog interacting with a vixen in an urban garden. North London, UK. July.

Matthew Maran / Red fox (Vulpes vulpes) cub defending its kill (a large dead Brown rat (Rattus norvegicus)) from another cub, North London, UK. August.

Morley Read / Slow motion clip of a group of male Mallards (Anas platyrhynchos) competing violently to mate with a single female, Cornwall, England, UK, May 2018.

Ingo Arndt / Female Puma (Puma concolor) with two cubs aged around four months, Torres del Paine National Park, Patagonia, Chile, July.

Heather Angel / Northern white cheeked gibbon (Nomascus leucogenys) female standing in tree with baby aged two weeks. Parents captive bred and released. Wild Elephant Valley / Xishuangbanna, Yunnan Province, China, 2...

Alex Mustard / Pair of Western clown anemonefish (Amphiprion ocellaris) spawning orange eggs on the rock beneath their Magnificent sea anemone (Heteractis magnifica) home on a coral reef. This photo shows the larger...

Alex Mustard / Two female Common seahorses (Hippocampus kuda) fighting over territory on the seabed. The brief fight was preceeded by a ritualised, synchronised parade. Bitung, North Sulawesi, Indonesia. Lembeh Stra...

Alex Mustard / Common seahorse (Hippocampus kuda) female wrapping her prehensile tail around piece of wood on the seabed. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Tony Wu / Humpback whale (Megaptera novaeangliae australis) female with suckling calf. Vava'u Islands, Tonga.

Felis Images / Asiatic lion (Panthera leo persica), female and cubs in morning light, cub biting mother's leg. Gir National Park, Gujarat, India. Photo© Phillip Ross/Felis Images

Ben Gillett / Slow motion clip of a female Appaloosa horse grooming a male, Bristol, England, UK, May.

Jack Dykinga / Burrowing owl (Athene cunicularia) female and ten chicks aged a few weeks. Marana, Arizona, USA. May.

John Shaw / Snow monkey or Japanese macaque (Macaca fuscata) female with baby clinging to her back. Jigokudani, Japan, February.

John Shaw / Common eider duck (Somateria mollissima) female defending her nest from arctic fox (Vulpes lagopus). Longyearbyen, Spitsbergen. June.

John Chan / Two male Southern Pacific rattlesnakes (Crotalus oreganus helleri) fighting during mating season. This behaviour is known as a "combat dance", and is used to determine dominance and the right to mate...

Jiri Lochman / Brush-tailed phascogale (Phascogale tapoatafa) female with young, Kingston Forest, Western Australia, October.

Phil Savoie / Yellow legged mining bee (Andrena flavipes) female at nest burrow, River Monnow, Monmouthshire, Wales, UK, April.

Nick Hawkins / A female American black bear (Ursus americanus) and her young cub, Nova Scotia, Canada. July.

Oriol Alamany / Snow leopard (Panthera uncia) female with juvenile, walking in snow, in Spiti Valley, Cold Desert Biosphere Reserve, Himalaya, Himachal Pradesh, India, March

Oriol Alamany / Snow leopard (Panthera uncia) female (hiding below the rock) with her two juveniles resting in snow, in Spiti Valley, Cold Desert Biosphere Reserve, Himalaya, Himachal Pradesh, India, March

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) dominant male (T29) and resident female (T27) cooling off in a watering hole Kanha National Park, Central India. Camera trap image.

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) dominant male (T29) and resident female (T27) cooling off in a waterhole Kanha National Park, Central India. Camera trap image.

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) female (T27) acting cautiously as dominant male (T29) approaches watering hole Kanha National Park, Central India. Camera trap image.