Daniel Heuclin / Yellow-bellied Puffing Snake (Pseustes sulphureus) moving towards the camera. French Guyana, August.

Daniel Heuclin / Puffing / Bird Eating / Twig Snake (Pseustes poecilonotus) in characteristic posture mimicking a twig. French Guyana, August.

Melvin Grey / Neotropical birdeater (Pseutes poecilonotus) adult snake with open mouth, breathing tube visible, Lowland Rainforest, Costa Rica

Melvin Grey / Neotropical birdeater (Pseutes poecilonotus) adult Lowland Rainforest, Costa Rica

Doug Wechsler / Shropshire's puffing snake (Pseustes shropshirei) Province El Oro, Buenaventura Reserve, Ecuador

Konrad Wothe / Puffing Snake (Pseustes poecilonotus), Panguana Nature Reserve, Peru

Yumiko Wakisaka / Harbor Porpoise (Phocoena phocoena)

Flip Nicklin / Researcher Jonathan Stern, Ph.D., of Golden Gate Cetacean Research reviewing Harbor Porpoise (Phocoena phocoena) id images, California

Steve Gettle / Rough-legged Hawk (Buteo lagopus) puffing up feathers to keep warm, Howell Nature Center, Michigan

Daniel Heuclin / Yellow-bellied Puffing Snake (Pseustes sulphureus) tasting the air as it moves through water. French Guyana, August.

Daniel Heuclin / Yellow-bellied Puffing Snake (Pseustes sulphureus) in sandy habitat. French Guyana, August.

Daniel Heuclin / Yellow-bellied Puffing Snake (Pseustes sulphureus) head in profile. French Guyana, August.

Daniel Heuclin / Puffing / Bird Eating / Twig Snake (Pseustes poecilonotus) in defensive strike-ready posture. French Guyana, August.

Daniel Heuclin / Puffing / Bird Eating / Twig Snake (Pseustes poecilonotus) in defensive strike-ready posture. French Guyana, August.

Daniel Heuclin / Puffing / Bird Eating / Twig Snake (Pseustes poecilonotus) in defensive strike-ready posture. French Guyana, August.

Daniel Heuclin / Puffing / Bird Eating / Twig Snake (Pseustes poecilonotus) in characteristic posture mimicking a twig. French Guyana, August.

Daniel Heuclin / Puffing / Bird Eating / Twig Snake (Pseustes poecilonotus) head in profile, aggressive "puffed" posture. French Guyana, August.

Tim Fitzharris / Greater Roadrunner (Geococcyx californianus) puffing out feathers to thermoregulate, Big Bend National Park, Texas

Scott Leslie / Pied-billed Grebe (Podilymbus podiceps) puffing its neck in a territorial display, Amherst Point Migratory Bird Sanctuary, Nova Scotia, Canada

Yva Momatiuk & John Eastcott / Atlantic Puffin (Fratercula arctica) close-up portrait of adult flapping wings and puffing up chest during summer breeding season, Newfoundland, Canada

Yva Momatiuk & John Eastcott / Atlantic Puffin (Fratercula arctica) close-up portrait of adult flapping wings and puffing up chest during summer breeding season, Newfoundland, Canada

Yva Momatiuk & John Eastcott / Atlantic Puffin (Fratercula arctica) portrait of adult flapping wings and puffing up chest during summer breeding season, Newfoundland, Canada

Tui De Roy / Harbor Porpoise (Phocoena phocoena) meat for sale at modern Inuit market, Nuuk, Greenland

Flip Nicklin / Harbor Porpoise (Phocoena phocoena) released by researcher Andrew Read which had been accidentally caught in a herring trap, Bay of Fundy, Canada

Flip Nicklin / Harbor Porpoise (Phocoena phocoena) which had been accidentally caught in a herring trap being hydrated by researchers and fisherman, Bay of Fundy, animal was subsequently tagged and released, Canada

Jeff Rotman / Masked pufferfish inflated at night {Arothron diadematus} Red Sea, Egypt

Joel Sartore / Photo Ark / White-headed lapwing (Vanellus albiceps) looking around before puffing up feathers, Lundi Farm. Captive.

Joel Sartore / Photo Ark / Hyacinth macaw (Anodorhynchus hyacinthinus) turning its head and puffing up feathers, Cincinnati Zoo. Captive.

Joel Sartore / Photo Ark / Black-headed parrot (Pionites melanocephalus pallidus) walking around and puffing up feathers, before leaving the frame, Parque de Las Leyendas, Peru. Captive.