Costa Rica covers 0.03 per cent of the planet's land surface and holds around five per cent of its biodiversity. That disproportion explains why most visitors end up organising their trip around what they want to see.
Sloths
There are two species: the three-toed sloth, with its permanent expression of a smile, and the larger, nocturnal two-toed sloth. They are readily found at Manuel Antonio, Cahuita, La Fortuna and along the southern Caribbean corridor. They sleep fifteen to twenty hours a day and barely move, so spotting them is a matter of a trained eye: a guide with a scope is the difference between seeing one and seeing six.
Birds
Around 920 species are recorded — more than the United States and Canada combined. The emblematic ones are the resplendent quetzal (Monteverde, San Gerardo de Dota, February to July), the keel-billed toucan and Swainson's toucan in the Caribbean lowlands, and the scarlet macaw on Osa and at Carara. Hummingbirds appear in any highland garden, sometimes eight or ten species at one feeder.
Monkeys
Four species: the howler, whose dawn roar carries more than a kilometre and startles everyone hearing it for the first time; the capuchin, clever and thieving; the spider monkey, shyer, in well-preserved forest; and the squirrel monkey, small and endangered, restricted to the central and southern Pacific.
Amphibians and reptiles
The red-eyed tree frog is the country's photographic icon, though it is nocturnal and must be looked for by torchlight in humid Caribbean areas. Poison dart frogs, tiny and intensely coloured, are active by day in the leaf litter. American crocodiles gather in the Tárcoles river — the bridge over it is a classic stop — and caimans inhabit the Tortuguero canals.
The sea
Costa Rica receives humpback whales in two seasons, which is almost unique: northern-hemisphere populations from December to April and southern ones from July to October. Bahía Ballena at Uvita is the best spot. Four species of sea turtle nest on its two coasts, with the Ostional arribadas and green turtle nesting at Tortuguero the main events.
How to see it
Two pieces of advice outweigh all others: hire local guides — they see what you never will — and go out at dawn. Animal activity concentrates in the first two hours of light and the last two of the afternoon. And touch nothing and feed nothing: it is illegal and it harms the animals.