Alouatta palliata
Drawn from open occurrence records in and around Tortuguero, aggregated onto a 10 km grid. A cell is matched by its centre, which can sit up to 16 km outside the boundary, so this covers the surrounding country too.
Occurrence records measure where people looked and found something, which is not the same as where the animal is. This is a relative likelihood, not a probability.
Records exist for January, February, March, April, May, June, July, August, September, October, November and December, with the widest coverage in April. A quiet month can mean the animal was absent, or that nobody was looking.
A grid cell is a square of the map, not a sighting: 13 squares of 10 km carry records for Mantled Howler Monkey in and around Tortuguero, and the 98 records behind them were collected by other people and published openly. Nothing here counts animals, and a place with more records is not always a place with more animals.
You will hear a mantled howler long before you see one, and possibly before you are fully awake: the dawn roar of a male carries three kilometers or more through wet forest, produced by a resonating throat bone that turns a ten-kilogram monkey into a public address system. The howl is real estate law, troops announcing position so that rival groups can avoid an actual fight neither can afford. Howlers run the rainforest's low-energy strategy: they eat leaves, which are abundant and nearly worthless, and pay for it by resting up to three quarters of the day, draped over branches like discarded coats. Troops of a dozen or two are a fixture of Costa Rican forest, mangrove and even roadside strips.
Never feed monkeys and keep distance at eye-contact height; habituated howlers end up electrocuted on roadside wires chasing handouts.