Nick Hawkins / Grey seal (Halichoerus grypus) opening mouth close up off Bonaventure Island, Gulf of Saint Lawrence, Quebec, Canada. September.
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Solvin Zankl / Fire Ant (Solenopsis geminata) head of a major worker with mandibles used for opening seeds. Specimen photographed using digital focus stacking
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Solvin Zankl / Just three hours after they hatch from the water and moult into mature adults, the male Long-tailed / Tisza mayfly (Palingenia longicauda) perish. Adult mayflies have no mouth opening and no guts. The...
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Mitsuaki Iwago / African Lion (Panthera leo) female roaring, Serengeti National Park, Tanzania
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Mark Raycroft / Brittany Spaniel (Canis familiaris) with training bumper
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Mark Moffett / Tokay Gecko (Gecko gecko) showing underside of feet
Shin Yoshino / African Lion (Panthera leo) male roaring, Kenya
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Mitsuaki Iwago / African Wild Dog (Lycaon pictus) calling, Serengeti National Park, Tanzania
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Gerry Ellis / Ostrich (Struthio camelus), east Africa
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Jim Brandenburg / Nile Crocodile (Crocodylus niloticus) mouth defense displaying, South Africa
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Mitsuaki Iwago / African Lion (Panthera leo) pride with one female snarling, Serengeti National Park, Tanzania
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Mike Parry / Saltwater Crocodile (Crocodylus porosus) underwater, South Australia.
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Yva Momatiuk & John Eastcott / Red Fox (Vulpes vulpes) kit yawning on ridge near den, North Slope, Alaska
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Norbert Wu / Great White Shark (Carcharodon carcharias) near divers in shark cage, Australia
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Matthias Breiter / Kodiak Bear (Ursus arctos middendorffi) with mouth agape, native to Kodiak Island, Alaska
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Konrad Wothe / Orangutan (Pongo pygmaeus) juvenile swinging in tree, Tanjung Puting National Park, Borneo
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Tui De Roy / Waved Albatross (Phoebastria irrorata) courtship display sequence, Punta Cevallos, Espanola Island, Galapagos Islands, Ecuador
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Fred Bavendam / Great White Shark (Carcharodon carcharias) attacking with mouth open as he launches from the water, Neptune Islands, South Australia
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Mitsuaki Iwago / Japanese Macaque (Macaca fuscata) group grooming with one calling, Japan
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Flip Nicklin / Bottlenose Dolphin (Tursiops truncatus) playing in shallow water, Hawaii
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Nick Hawkins / Grey seal (Halichoerus grypus) opening mouth off Bonaventure Island, Gulf of Saint Lawrence, Quebec, Canada. September.
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Tony Wu / Hairy frogfish (Antennarius striatus) opening its mouth whilst searching for food. Lembeh Strait, Celebes Sea, North Sulawesi, Indonesia.
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Jeff Rotman / Zebra Shark (Stegostoma fasciatum) underside showing mouth, teeth, barbels, ampullae of Lorenzini (natural electrical detectors located in the heads of sharks and rays which are sensitive to the elect...
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Sue Daly / Male Cuckoo wrasse (Labrus mixtus) opening mouth, before swimming out of the frame, Sark, British Channel Islands, UK, July.
Bertie Gregory / Giant moray eel (Gymnothorax javanicus) opening its mouth to breathe, at night on the barge wreck, Gubal Island, northern Red Sea.
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Bertie Gregory / Giant moray eel (Gymnothorax javanicus) opening its mouth to breathe, at night on the barge wreck, Gubal Island, northern Red Sea.
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Tony Wu / Humpback whale (Megaptera novaeangliae) male calf opening his mouth whilst playing with mother and escort, Vava'u, Tonga, South Pacific
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Daniel Heuclin / Forest cobra (Naja melanoleuca) with mouth open showing the glottis, the opening to the windpipe, on white background, captive occurs in Africa. Venomous species.
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Donald M. Jones / American Badger (Taxidea taxus) baring its teeth at den entrance, Montana
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Staffan Widstrand / The Bar mouth, opening into the sea, Pulicat Lake, Tamil Nadu, India, February 2013.
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Cyril Ruoso / Bonobo (Pan paniscus) female orphan calling, Sanctuary Lola Ya Bonobo Chimpanzee, Democratic Republic of the Congo
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Cyril Ruoso / Komodo Dragon (Varanus komodoensis) regulating temperature by opening mouth, Rinca Island, Komodo National Park, Indonesia
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Cyril Ruoso / Komodo Dragon (Varanus komodoensis) regulating temperature by opening mouth, Rinca Island, Komodo National Park, Indonesia
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Luiz Claudio Marigo / Yacare Caiman (Caiman yacare) opening its mouth. The Pantanal wetlands of Mato Grosso State, Brazil, October.
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Suzi Eszterhas / Gray Whale (Eschrichtius robustus) opening mouth and showing baleen plates, San Ignacio Lagoon, Baja California, Mexico
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Hiroya Minakuchi / Orca (Orcinus orca) opening mouth for food in aquarium, native to the Pacific
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Andy Rouse / Saltwater crocodile (Crocodylus porosus) opening mouth, Northern Territories, Australia
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Luciano Candisani / Jacare Caiman (Caiman yacare) group fishing by opening mouths and waiting for prey, Pantanal Ecosystem, Brazil
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Mitsuaki Iwago / African Lion (Panthera leo) female roaring, Serengeti National Park, Tanzania
Winfried Wisniewski / Waved Albatross (Phoebastria irrorata) courting pair engaged in bill clappering
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Pete Oxford / Mountain Sipo (Chironius monticola) defensive posture with mouth open, Mindo cloud forest ecosystem, Ecuador
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Mitsuaki Iwago / African Lion (Panthera leo) female yawning, Serengeti National Park, Tanzania
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Mitsuaki Iwago / African Lion (Panthera leo) male roaring after rainstorm, Serengeti National Park, Tanzania
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Mitsuaki Iwago / African Lion (Panthera leo) male approaching female to mate, Serengeti National Park, Tanzania
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Mitsuaki Iwago / African Lion (Panthera leo) male growling, Serengeti National Park, Tanzania
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Mitsuaki Iwago / Cheetah (Acinonyx jubatus) growling, Serengeti, Tanzania
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Mitsuaki Iwago / Spotted Hyena (Crocuta crocuta) calling, Serengeti, east Africa
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Yva Momatiuk & John Eastcott / Blue Monkey (Cercopithecus mitis) in forest with mouth agape, Masai Mara National Reserve, Kenya
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Hiroya Minakuchi / Southern Elephant Seal (Mirounga leonina) male roaring, Falkland Islands
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Sumio Harada / Black-footed Ferret (Mustela nigripes) calling from burrow in ground, recently released from captive breeding program, Fort Belknap Indian Reservation, Montana
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Claus Meyer / Jacare Caiman (Caiman yacare) resting in shallow water, thermoregulating by opening jaws, Pantanal ecosystem, Brazil
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Claus Meyer / Green Iguana (Iguana iguana) portrait, Caatinga ecosystem, Brazil
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Duncan Usher / Eurasian Wren (Troglodytes troglodytes) parent at nest with four hungry chicks, Europe
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Mike Parry / Great White Shark (Carcharodon carcharias) breaking surface of water to feed, Neptune Islands, south Australia
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Mike Parry / Great White Shark (Carcharodon carcharias) feeding from baited line, Neptune Islands, South Australia
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Mike Parry / Great White Shark (Carcharodon carcharias) feeding from baited line, Neptune Islands, South Australia
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Heidi & Hans-Juergen Koch / Egg-eating Snake (Dasypeltis sp) opens it's mouth to swallow a bird egg, specially adapted to eat bird eggs, native to Africa
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Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) exhausted mother rests outside of her nest full of babies in a tree trunk, Rocky Mountains, North America
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Konrad Wothe / Siberian Tiger (Panthera tigris altaica) yawning in snow storm, Siberian Tiger Park, Harbin, China
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Hiroya Minakuchi / Gray Whale (Eschrichtius robustus) pet by tourists in boat, San Ignacio Lagoon, Baja California, Mexico
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Hiroya Minakuchi / Gray Whale (Eschrichtius robustus) pet by tourists in boat, San Ignacio Lagoon, Baja California, Mexico
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Konrad Wothe / Southern Elephant Seal (Mirounga leonina) pair calling, Macquarie Island, Australia
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Katherine Feng / Giant Panda (Ailuropoda melanoleuca) baby sitting on ground in bamboo forest at the China Conservation and Research Center for the Giant Panda, Wolong Nature Reserve, China
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Thomas Mangelsen / Bohemian Waxwing (Bombycilla garrulus) eating berries on tree, southwest Montana
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Mike Parry / Saltwater Crocodile (Crocodylus porosus) aggressive posture, Oro Bay, Papua New Guinea
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Tim Fitzharris / Grizzly Bear (Ursus arctos horribilis) calling, North America
Duncan Usher / Eurasian Wren (Troglodytes troglodytes) chicks in nest, Europe
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Heidi & Hans-Juergen Koch / Colubrid Snake (Elaphe sp) two making initial contact, using tongue (Nasovomeral sense) to identify friend, enemy, or prey
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Tim Fitzharris / Grizzly Bear (Ursus arctos horribilis) calling, North America
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Tim Fitzharris / Grizzly Bear (Ursus arctos horribilis) calling, North America
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Konrad Wothe / Jacare Caiman (Caiman yacare) thermoregulating by opening jaws, Pantanal, Brazil
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Konrad Wothe / Lion-tailed Macaque (Macaca silenus) calling, India
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Michael Quinton / Common Raven (Corvus corax) using its beak to open a snowmobile's storage compartment in search of food, Yellowstone National Park, Wyoming
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Tui De Roy / Galapagos Penguin (Spheniscus mendiculus) braying to attract mate, Cape Douglas, Fernandina Island, Galapagos Islands, Ecuador
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Tui De Roy / Masked Booby (Sula dactylatra) calling at nest site, Tower Island, Galapagos Islands, Ecuador
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Tui De Roy / Masked Booby (Sula dactylatra) calling, Tower Island, Galapagos Islands, Ecuador
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Tui De Roy / Masked Booby (Sula dactylatra) yawning, Hood Island, Galapagos Islands, Ecuador
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Tui De Roy / Komodo Dragon (Varanus komodoensis) yawning juvenile, Komodo National Park, Komodo Island, Indonesia
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Tui De Roy / Southern Royal Albatross (Diomedea epomophora) courtship display, Campbell Island, New Zealand