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

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) mother nursing calf, Newfoundland, Canada

Suzi Eszterhas / Leopard (Panthera pardus) six-week-old cub nursing, Jao Reserve, Botswana

Eric Baccega / Female Uganda kob (Kobus kob thomasi) suckling calf. Murchisson Falls National Park, Uganda. February.

Luke Massey / Wild boar (Sus scrofa) piglets suckling from mother, Forest of Dean, Gloucestershire, England, UK, May.

Philippe Clement / European brown bear (Ursus arctos arctos) cubs suckling from mother in the snow in winter, Bavarian Forest National Park, Germany, January. Captive.

Dave Bevan / Juvenile Herring gull (Larus argentatus) pecking a suckling Grey seal (Halichoerus grypus) pup, Norfolk, England, UK. December.

Brian Bevan / Grey seal (Halichoerus grypus) pup trying to suckle, Norfolk, England, UK, January.

Ingo Arndt / Eastern grey kangaroo with joey suckling (Macropus giganteus) Australia

Ingo Arndt / Dromedary camel suckling {Camelus dromedarius} Rajasthan, India

Sam Hobson / Red fox vixen (Vulpes vulpes) with young cubs. Bristol, UK. April

Cyril Ruoso / Golden monkey (Rhinopithecus roxellana) female with young suckling, Qinling Mountains, China.

Cyril Ruoso / Golden monkey (Rhinopithecus roxellana) adult male and female hugging, Qinling Mountains, China.

Edwin Giesbers / Western lowland gorilla (Gorilla gorilla gorilla) twin babies age 45 days resting on mother's chest, one suckling. captive, occurs in Central Africa. Critically endangered.

Anup Shah / Eastern chimpanzee (Pan troglodytes schweinfurtheii) young baby of adolescent female 'Golden' suckling. Gombe National Park, Tanzania.

Pascal Pittorino / Corsican pig (Sus scrofa domestica) sow, suckling the piglets, Parc Naturel Regional de Corse / Natural Regional Park of Corsica, Corsica Island, France. September.

Cyril Ruoso / Western lowland gorilla (Gorilla gorilla gorilla) female suckling baby, captive at Monkey Valley Zoo. Non-ex

Suzi Eszterhas / Proboscis Monkey (Nasalis larvatus) mother nursing four month old baby, Sabah, Borneo, Malaysia

Aflo / Japanese macaque (Macaca fuscata) mother cuddling baby, Yamanouchi, Shimotakai District, Nagano Prefecture, Japan. June.

Suzi Eszterhas / Capybara (Hydrochoerus hydrochaeris) mother nursing young, Pantanal, Brazil

Suzi Eszterhas / Bengal Tiger (Panthera tigris tigris) cubs age eight weeks, suckling. Bandhavgarh National Park, India.

Laurent Geslin / Red fox {Vulpes vulpes} female with three cubs suckling, UK

Fiona Rogers / Celebes / Black crested macaque (Macaca nigra) female with suckling infant aged 9-12 months, Tangkoko National Park, Sulawesi, Indonesia.

Fiona Rogers / Western chimpazee (Pan troglodytes verus) female 'Fanle' aged 13 years with suckling infant male 'Flanle' aged 3 years, Bossou Forest, Mont Nimba, Guinea. January 2011.

Steven Kazlowski / Moose (Alces alces) cow suckling her newborn calves. Tony Knowles Coastal Trail, Anchorage, south-central Alaska, May.

Florian Möllers / Quinling Golden snub nosed Monkey (Rhinopitecus roxellana qinlingensis), infant suckling Zhouzhi Nature Reserve, Qinling Mountains, Shaanxi, China.

Nick Turner / Gloucester old spot piglets (Sus scrofa domestica) suckling at the Cotswold Farm Show, Cirencester, UK, July 2008.

Nick Turner / Gloucester old spot piglets (Sus scrofa domestica) suckling at the Cotswold Farm Show, Cirencester, UK, July 2008.

David Woodfall / Grey Seal (Halichoerus grypus ) pup, 3 weeks, suckling. Donna Nook, UK, November.

Anup Shah / Caracal (Caracal caracal) two six month kittens suckling from mother, Masai Mara National Reserve, Kenya, August

Laurent Geslin / Two Southern plains grey / Hanuman langur {Semnopithecus dussumieri} females suckling young, Sariska NP, India

Anup Shah / Bonobo (Pan paniscus) baby aged 9-12 months, portrait, Lola Ya Bonobo Sanctuary, Democratic Republic of Congo. October.

Luiz Claudio Marigo / Capybara (Hydrochoeris hydrochaeris) mother with two suckling infants. The Pantanal wetlands of Mato Grosso State, Brazil, October.

Florian Möllers / Red fox (Vulpes vulpes) vixen nursing cubs in garden of block of flats, Berlin, Germany. May 2006

Anup Shah / Lion cub (Panthera leo) aged less than 2 days crying for its mother's attention while others suckle. Masai Mara National Reserve, Kenya, September 2009

Edwin Giesbers / Wild boar (Sus scrofa) female with piglets from two different litters, the Netherlands, April

Petra Wegner / British Longhair Cat (Highlander, Lowlander, Britanica) blue-cream-white coated, lying and nursing ginger kittens, aged 2 weeks.

Petra Wegner / British Longhair Cat (Highlander, Lowlander, Britanica) blue-cream-white coated, cloe up lying and nursing ginger kittens, aged 2 weeks.

Petra Wegner / British Longhair Cat (Highlander, Lowlander, Britanica) blue-cream-white coated, lying and nursing ginger kittens, aged 2 weeks.

Petra Wegner / British Longhair Cat, blue-cream-silver-tabby-mackerel (Highlander, Lowlander, Britanica) lying down with kittens, aged 3 weeks.

Petra Wegner / British Longhair Cat, blue-cream-silver-tabby-mackerel (Highlander, Lowlander, Britanica) lying down with kittens, aged 3 weeks.

Petra Wegner / British Longhair Cat, blue-cream-silver-tabby-mackerel (Highlander, Lowlander, Britanica) lying down and grooming ginger kitten, aged 3 weeks.

Petra Wegner / British Longhair Cat, blue-cream-silver-tabby-mackerel (Highlander, Lowlander, Britanica) lying down and grooming ginger kitten, aged 3 weeks.

Anup Shah / Impala herd (Aepyceros melampus) and female with suckling fawn in late afternoon rain, Masai Mara National Reserve, Kenya. March.

Anup Shah / African elephant (Loxodonta africana) calf aged 3-6 months wanting to suckle, Masai Mara National Reserve, Kenya. March.

Wild Wonders of Europe / Shpilenok / Saiga antelope (Saiga tatarica) with two calves suckling near Cherniye Zemli (Black Earth) Nature Reserve, Kalmykia, Russia, May 2009

Guy Edwardes / Young Grey Seal {Halichoerus grypus} taking a break from suckling from mother, Donna Nook, Lincolnshire, England, January

Dan Burton / Piglets suckling {Sus scrofa domestica} UK

Anup Shah / Leopard {Panthera pardus} with young suckling, Serengeti NP, Tanzania

Yva Momatiuk & John Eastcott / Masai Giraffe (Giraffa tippelskirchi) mother nursing newborn, Masai Mara, Kenya

Jean-Pierre Zwaenepoel / Southern plains grey / Hanuman langur {Semnopithecus dussumieri} mother and young sitting on roof, Jodhpur, India

Jane Burton / Domestic Cat {Felis catus} Tabby mother suckling her kittens.

Hermann Brehm / Argentine grey / Patagonian fox suckling young {Pseudolopex griseus} Torres del Paine NP, Chile

Jane Burton / Domestic cat (Felis catus) suckling 2/3-week-old kittens

Colin Seddon / Suckler cow suckling calf {Bos taurus} on organic Farm, Berkshire, England UK

Mike Wilkes / Exmoor pony mare {Equus caballus} and foal suckling. Exmoor National Park, UK.

Mary McDonald / Harp seal pup {Phoca groenlandicus} suckling. Canada.

LYNN M. STONE / Domestic Texas longhorn cow suckling calf {Bos taurus}, Texas Hill Country, USA

Mats Forsberg / Ringed seal pup suckling {Phoca hispida} Svalbard, Norway

Pete Cairns / Eriskay pony with foal suckling {Equus caballus} South Uist, Scotland, UK

David Welling / Common seal mother feeding 2 day pup {Phoca vitulina} La Jolla Cove, California, USA

Anup Shah / Orang utan mother with baby suckling, (Pongo abelii) Gunung Leuser NP, Indonesia

Anup Shah / Cheetah mother suckling cubs in lair in long grass {Acinonyx jubatus} Masai Mara

Anup Shah / Leopard suckling cub {Panthera pardus}, Masai Mara Game Reserve, Kenya

Gerry Ellis / African Elephant (Loxodonta africana) infant begging mother to nurse, Amboseli National Park, Kenya

Matthias Breiter / Grizzly Bear (Ursus arctos horribilis) adult female nursing her two yearling cubs on sedge flats, Katmai National Park, Alaska

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing her 19 day old babies in nest in tree trunk, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing her 15 day old babies in nest, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing babies in nest, Rocky Mountains, North America

Jim Brandenburg / American Bison (Bison bison) mother with nursing calf, South Dakota

Tui De Roy / Galapagos Sea Lion (Zalophus wollebaeki) newborn pup nursing, Cape Douglas, Fernandina Island, Galapagos Islands, Ecuador

Anup Shah / Cheetah mother suckling very young cubs {Acinonyx jubatus} Masai Mara, Kenya

Anup Shah / Leopard suckling cubs {Panthera pardus} Masai Mara, Kenya

Anup Shah / African elephant mother with suckling calf {Loxodonta africana} Masai Mara, Kenya

TJ Rich / Roe deer mother suckling fawn {Capreolus capreolus} UK

TJ Rich / Roe deer mother suckling fawn {Capreolus capreolus} UK

Karl Ammann / Olive baboon mother with young {Papio anubis} Samburu Reserve, Kenya

Andrew Cooper / Red Fox vixen suckling cubs in den, Devon, England.

Anup Shah / Newborn Common zebra foal suckling {Equus quagga} Masai Mara NR, Kenya

Jabruson / Mountain gorilla family, mother suckling young + male silverback in background {Gorilla g beringei} Virunga NP, Dem Rep Congo

Asgeir Helgestad / European Brown bear suckling cubs {Ursus arctos} Finland

Nick Gordon / Jaguar female and 4-day-old cub in birth den {Panthera onca} Amazonia, Brazil, South America. Captive.

Anup Shah / Lion female suckling litter Masai Mara, Kenya

Anup Shah / Giraffe suckling with male testing urine of female Giraffa camelopardalis} Kenya

Eric Baccega / Young Eastern White-bearded Wildebeest suckling mother (Connochaetes taurinus) Masai Mara National Reserve, Kenya.

Hanne & Jens Eriksen / Dromedary (Camelus dromedarius) female and newborn calf, calf suckling. Oman, March.

Hanne & Jens Eriksen / Dromedary (Camelus dromedarius) female and newborn calf, calf suckling. Oman, March.

Ann & Steve Toon / Yellow mongoose (Cynictis penicillata) suckling young, Kgalagadi Transfrontier National Park, Northern Cape, South Africa, February

Ann & Steve Toon / Yellow mongoose (Cynictis penicillata) suckling youngKgalagadi Transfrontier National Park, Northern Cape, South Africa, February

Edwin Giesbers / Grey seal (Halichoerus grypus), mother with suckling pup. Heligoland, Germany.

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.

Steven David Miller / Little red flying fox (Pteropus scapulatus), two hanging from branch with suckling young. Nitmiluk National Park, Northern Territory, Australia.

Steven David Miller / Little red flying fox (Pteropus scapulatus) female and suckling baby in flight, searching for place to roost. Nitmiluk National Park, Northern Territory, Australia.

Dong Lei / Rhesus macaque (Macaca mulatta) with baby suckling, Yarlung Zangbo River, Qinghai Tibet Plateau, China.

Suzi Eszterhas / Leopard (Panthera pardus) six-week-old cub nursing, Jao Reserve, Botswana