Brown-throated sloth, Puerto Viejo de Talamanca, Costa Rica

Brown-throated sloth, Puerto Viejo de Talamanca, Costa Rica

Slow and steady wins the race—and the brown-throated sloth seems perfectly happy to skip the race altogether. This three-toed mammal has a different approach to life: conserve energy, hang on and take your time.

Native to Central and South America, it spends much of its life upside down in the forest canopy. Its coarse fur hosts algae, fungi and specialised sloth moths, creating a tiny ecosystem on its back. The algae can even give its coat a greenish tint, helping it blend into the foliage. Its unusual anatomy helps it thrive in the treetops. Its extra neck vertebrae allow it to turn its head up to 270 degrees.

Even digestion takes the slow lane. Its multi-chambered stomach helps break down tough, fibrous leaves. About once a week, it makes a risky trip to the forest floor to defecate. And despite its sluggish reputation, it is also a surprisingly capable swimmer.