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

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

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

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

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

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

Sumio Harada / Mountain Goat (Oreamnos americanus) vocalizing, Rocky Mountains, North America

Michael Quinton / Common Raven (Corvus corax) calling while perched next to its nest in a pine tree, North America

Michael Quinton / Common Raven (Corvus corax) calling while perched next to its nest in a pine tree, North America

Michael Quinton / Common Raven (Corvus corax) orphaned chicks at rehabilitation center calling for food, North America

Flip Nicklin / Long-finned Pilot Whale (Globicephala melas) portrait, North America

Michael Quinton / Common Raven (Corvus corax) calling, North America