Cold Tolerant
Vascular counter-current heat exchangers and cellular cryoprotectants that keep blood flowing in freezing temperatures.

American Pika
A rabbit relative that stacks hay in summer and can be killed by two hours above 28°C.

Arctic Fox
Feet kept just above the point where living tissue freezes, a coat color set by one gene, and satellite-tracked treks of up to 40 kilometers to hotspots on the sea ice.

Common European Adder
A zigzag-backed viper that lives from Britain to the Pacific and is the only snake north of the Arctic Circle in Scandinavia.

Domestic Yak
Oversized heart and lungs, a shaggy coat and a home up to 5,000 m high.

Muskox
Bulls settle rivalries by charging 50 yards or more and colliding head-first on their horn bosses.