Richard Du Toit / Burchell's Zebra (Equus burchellii) yawning, Rietvlei Nature Reserve, Gauteng, South Africa

Richard Du Toit / Burchell's Zebra (Equus burchellii) pair, Rietvlei Nature Reserve, Gauteng, South Africa

Fergus Gill / 2020VISION / Skylark (Alauda arvensis) perched on a fence post, vocalising, Balranald RSPB reserve, North Uist, Outer Hebrides, Scotland, UK, June. Did you know? The collective noun for a group of Skylarks is an e...

Fergus Gill / 2020VISION / Redshank (Tringa totanus) perched on a fence post, vocalising, Balranald RSPB reserve, North Uist, Outer Hebrides, Scotland, UK, June 2012.

Fergus Gill / 2020VISION / Redshank (Tringa totanus) perched on a fencepost, vocalising, Balranald RSPB reserve, North Uist, Outer Hebrides, Scotland, UK, June 2012.

Fergus Gill / 2020VISION / Redshank (Tringa totanus) vocalising, Balranald RSPB reserve, North Uist, Outer Hebrides, Scotland, UK, June 2012.

Bertie Gregory / 2020VISION / Juvenile male Peregrine falcon (Falco peregrinus) vocalising as its parent takes off, Bristol, England, UK, June.

Andy Trowbridge / Yellow-eyed Penguins (Megadyptes antipodes) vocalising with chick. Endangered species. Katiki Point, Moeraki, Otago, New Zealand. January.

Donald M. Jones / Elk (Cervus elaphus) bull bugling, Jasper National Park, Alberta, Canada

Donald M. Jones / Elk (Cervus elaphus) bull bugling, Jasper National Park, Alberta, Canada

Andrew Parkinson / Sedge warbler (Acrocephalus schoenobaenus) singing portrait, Saltee Islands, Republic of Ireland, May.

Andy Rouse / Lonnberg's / Subantarctic Skua (Stercoraius antarcticus lonnbergi) displaying aggressive behaviour, South Shetland Islands, Antarctica. (Non-ex)

Konrad Wothe / European Bee-eater (Merops apiaster) trio calling, Bulgaria

Thomas Marent / European Tree Frog (Hyla arborea) calling, Switzerland

Steve Gettle / Golden-winged Warbler (Vermivora chrysoptera) calling, Michigan

Steve Gettle / Cape May Warbler (Setophaga tigrina) male calling, Crane Creek State Park, Ohio

Steve Gettle / Common Yellowthroat (Geothlypis trichas) male calling, Huron Meadows Metropark, Michigan

Steve Gettle / Red-winged Blackbird (Agelaius phoeniceus) male calling, Kensington Metropark, Michigan

Donald M. Jones / Eastern Warbling-Vireo (Vireo gilvus) male singing, northwest Montana

Donald M. Jones / Cactus Wren (Campylorhynchus brunneicapillus) singing from atop a flowering Ocotillo (Fouquieria splendens), southern Arizona

Gerrit Vyn / Willow Ptarmigan (Lagopus lagopus) male standing on snow covered ground, vocalising in spring courtship. Males retain the white body plumage of winter plumage and molt the head and neck feathers to th...

Edwin Giesbers / Arctic tern (Sterna paradisaea) in flight, vocalising, aggresive behaviour, Farne Islands, Northumberland, UK, June

Suzi Eszterhas / Sumatran Orangutan (Pongo abelii) two and a half year old baby calling, Gunung Leuser National Park, north Sumatra, Indonesia

Patricio Robles Gil / "Male Baja California / Peninsular pronghorn (Antilocapra americana peninsularis) vocalising, semicaptive breeding facility, Biosphere Reserva of El Vizcano, Baja, Mexico, Critically endangered subspe...

Donald M. Jones / American Pika (Ochotona princeps) calling from atop a boulder, Glacier National Park, Montana

Sebastian Kennerknecht / Ring-necked Duck (Aythya collaris) drake in breeding plumage calling, Santa Cruz, Monterey Bay, California

Donald M. Jones / American Elk (Cervus elaphus nelsoni) bull bugling, western Montana

Donald M. Jones / Black-tailed Prairie Dog (Cynomys ludovicianus) standing and barking, eastern Montana

Kevin Schafer / Amazon River Dolphin (Inia geoffrensis) swimming, Rio Negro, Amazonia, Brazil

Wild Wonders of Europe / Varesvuo / European Roller (Coracias garrulus) pair vocalising, Pusztaszer, Hungary, May 2008

Wild Wonders of Europe / Varesvuo / European Bee-eater (Merops apiaster) vocalising, Pusztaszer, Hungary, May 2008

Wild Wonders of Europe / E Haarberg / Chamois (Rupicapra rupicapra) male vocalising in rut, Gran Paradiso National Park, Italy, November 2008

Donald M. Jones / Common Yellowthroat (Geothlypis trichas) male singing, western Montana

Thomas Marent / Red Howler Monkey (Alouatta seniculus) calling, Peru

Vincent Grafhorst / African Lion (Panthera leo) male roaring, Moremi Game Reserve, Okavango Delta, Botswana

Kevin Schafer / Red-breasted Toucan (Ramphastos dicolorus) calling, Itatiaia National Park, Brazil

Yva Momatiuk & John Eastcott / Southern Elephant Seal (Mirounga leonina) pups, fat and docile weaners stay together for company and reassurance, St. Andrews Bay, South Georgia Island

Ingo Arndt / Alpine Marmot (Marmota marmota) calling, Austria

Ingo Arndt / Gelada Baboon (Theropithecus gelada) male calling, Simien Mountain National Park, Ethiopia

Yva Momatiuk & John Eastcott / Southern Elephant Seal (Mirounga leonina) bull roaring at intruder on beach during breeding season, Gold Harbour, South Georgia Island

Thomas Marent / Eclectus Parrot (Eclectus roratus) male calling, Daintree National Park, Australia

Jan Vermeer / Emperor Penguin (Aptenodytes forsteri) chick pair, Snow Hill Island, Antarctica

Hiroya Minakuchi / Beluga (Delphinapterus leucas) whale trio calling, vulnerable, Shimane Aquarium, Japan

Scott Leslie / American Toad (Bufo americanus) calling in spring pond, West Stoney Lake, Nova Scotia, Canada. Sequence 1 of 2

Richard Du Toit / Burchell's Zebra (Equus burchellii) close-up of face of braying animal, Hluhluwe-umfolozi Game Reserve, South Africa

Konrad Wothe / California Sea Lion (Zalophus californianus) with mouth open in threat display blowing bubbles, North America

Tim Fitzharris / Gray Wolf (canis lupus) howling, North America

Mitsuaki Iwago / African Lion (Panthera leo) female roaring, Serengeti National Park, Tanzania

Eric Baccega / Siamang Gibbon (Hylobates syndactylus) vocalising, vocal pouch inflated, captive, native to forests of Malaysia, Sumatra and Thailand

Ingo Arndt / Alpine Marmot (Marmota marmota) showing sharp teeth while calling, Hohe Tauern National Park, Austria

Ingo Arndt / Mountain Gorilla (Gorilla gorilla beringei) baby, Parc National Des Volcans, Rwanda

Ingo Arndt / Leopard Seal (Hydrurga leptonyx) barking, Weddell Sea, Antarctica

Suzi Eszterhas / African Lion (Panthera leo) five to six week old cub resisting being picked up by its mother, vulnerable, Masai Mara National Reserve, Kenya

Tui De Roy / Waved Albatross (Phoebastria irrorata) courtship dance under rainy season clouds, Punta Cevallos, Espanola Island, Galapagos Islands, Ecuador

ZSSD / East African River Hippopotamus (Hippopotamus amphibius kiboko) with open mouth in threat posture, native to Africa

John Cancalosi / Rhum pony, mouth wide open, Isle of Rhum, Scotland, UK.

Pete Oxford / Red-legged Seriema (Cariama cristata) threat display, Brazil

Patricio Robles Gil / African Pygmy Elephant (Loxodonta pumilio) vocalizing with trunk raised, Petit Loango National Park, Gabon, western Africa

Richard Du Toit / African Lion (Panthera leo) adult male roaring at night, Sabi Sands Private Game Reserve, South Africa

ZSSD / Western Lowland Gorilla (Gorilla gorilla gorilla) male vocalizing, native to equatorial West Africa

Shin Yoshino / African Lion (Panthera leo) male roaring, Kenya

Yva Momatiuk & John Eastcott / African Lion (Panthera leo) adult male followed by curious and playful six and three month old cubs, Masai Mara National Reserve, Kenya

Gerry Ellis / Ostrich (Struthio camelus), east Africa

Gerry Ellis / Chimpanzee (Pan troglodytes) pair interacting, Gombe Stream National Park, Tanzania

Mitsuaki Iwago / African Lion (Panthera leo) pride with one female snarling, Serengeti National Park, Tanzania

Konrad Wothe / African Lion (Panthera leo) family of adult females and cubs on fallen tree, Serengeti, Tanzania

Konrad Wothe / Virginia Opossum (Didelphis virginiana) female hissing from tree cavity, North America

Claus Meyer / Toco Toucan (Ramphastos toco) calling while perching on branch, Cerrado, Brazil

Claus Meyer / Emperor Tamarin (Saguinus imperator) calling, Amazon, Brazil

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) climbing tree, Rocky Mountains, North America

Konrad Wothe / Fisher (Martes pennanti) baby calling from tree cavity, North America

Konrad Wothe / Barn Swallow (Hirundo rustica) chicks lined up in nest with their mouths open waiting for food, Germany

Konrad Wothe / Gyrfalcon (Falco rusticolus) adult female calling, North America

Konrad Wothe / Whooper Swan (Cygnus cygnus) pair arguing at wintering site, Kussharo-ko, Hokkaido, Japan

Konrad Wothe / Black-crowned Night Heron (Nycticorax nycticorax) calling, Europe

Yva Momatiuk & John Eastcott / African Lion (Panthera leo) adult male with full mane roaring to assert dominance, Masai Mara National Reserve, Kenya

Thomas Mangelsen / Bald Eagle (Haliaeetus leucocephalus) calling, Southeast Alaska

Tim Fitzharris / Timber Wolf (Canis lupus) pair howling in snow, North America

Tim Fitzharris / Timber Wolf (Canis lupus) pair howling in snow, North America

Pete Oxford / Alpaca (Lama pacos) baby, Andes Mountains, South America

Yva Momatiuk & John Eastcott / Grizzly Bear (Ursus arctos horribilis) pair of young males fighting, Katmai National Park, Alaska

Gordon Court / Adelie Penguin (Pygoscelis adeliae) gives a warning call when under threat, Cape Bird, Ross Island, Antarctica

Konrad Wothe / Edible Frog (Rana esculenta) croaking, Germany

Konrad Wothe / Edible Frog (Rana esculenta) croaking in pond, Germany

Thomas Mangelsen / Bald Eagle (Haliaeetus leucocephalus) adults on snags, North America

Gerry Ellis / Timber Wolf (Canis lupus) howling, temperate North America

Michael & Patricia Fogden / Southern Grasshopper Mouse (Onychomys torridus) male singing on its territory, Chihuahua Desert, Mexico

Gerry Ellis / Asian Elephant (Elephas maximus) profile, India

Gerry Ellis / Orangutan (Pongo pygmaeus) hanging on tree, Sepilok Forest Reserve, Sabah, Borneo

Konrad Wothe / Red-crowned Crane (Grus japonensis) pair calling during courtship dance at their wintering grounds, Hokkaido, Japan

Konrad Wothe / Blue Tit (Cyanistes caeruleus) parent delivering caterpillar to chicks in nest, Europe

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother protecting territory near her nest from other squirrels, Rocky Mountains, North America

Gerry Ellis / Tawny Frogmouth (Podargus strigoides), Australia

Gerry Ellis / White-faced Capuchin (Cebus capucinus) monkey calling, Corcovado National Park, Costa Rica

Michio Hoshino / Caribou (Rangifer tarandus) bull calling on autumn tundra, Alaska

Konrad Wothe / Red-crowned Crane (Grus japonensis) couple in courtship display, Hokkaido, Japan