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

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

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

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

Yva Momatiuk & John Eastcott / Red Fox (Vulpes vulpes) kit yawning on ridge near den, North Slope, Alaska

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) stallion yawning in evening sunlight, Wyoming

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) stallion yawning, Wyoming

Gerry Ellis / Bengal Tiger (Panthera tigris tigris) yawning, Hilo Zoo, Hawaii

Larry Minden / Desert Tortoise (Gopherus agassizii) in a field of yellow flowers, Mojave Desert, California

Jim Brandenburg / Cottontail Rabbit (Sylvilagus aquaticus) yawning, South Dakota

Michael Quinton / Bobcat (Lynx rufus) kitten yawning while resting on a log in summer, Idaho

Tui De Roy / Galapagos Giant Tortoise (Chelonoidis nigra) yawning, Alcedo Volcano, Isabella Island, Galapagos Islands, Ecuador