Animals in Costa Rica
Monkeys
Four different species of monkeys are found in Costa Rica:

Howler Monkeys (Congos)
The sounds of howler monkeys sound terrifying for a first-time visitor in Costa Rica but they are very peaceful vegetarians. Take care however not to stand beneath a howler monkey family as they use an effective strategy to steer away obnoxious humans: they just pee - with the most innocent face you can imagine.
With their consumption of new leaves and shoots the monkeys increase branching and the eventual fruit production of some tree species. Howler monkeys rarely set their feet on the ground, they only travel trough the canopy. Construction development with clearing of forests has cut off many of their travel routes so that in the last 15 years Costa Rica's howler monkey population has declined by 50%.
While deforestation is the main reason for the decrease of monkey populations in Costa Rica, many monkeys also end up being electrocuted on uninsulated power lines. The monkeys have to use these lines as an alternative when their travel routes have been cut.

Capuchin Monkeys (Cara Blanca)
The White-Faced Capuchin Monkeys are easily seen in Costa Rica. They live in groups of 5 to 24 animals. These monkeys are extremely curious, agile and aggressive, defending their territory by threatening with their sharp teeth and shaking on trees. They primarily feed on fruit and are considered important in dispersing the seeds of many trees. Capuchin monkeys are particularly fond of bananas. If you dare to refuse them THEIR bananas they can become really naughty.
Despite their cute looks the little rascals are in fact highly efficient predators. Their main diet consists of fruits and leaves, but they also eat insects and lizards, birds and their eggs, even baby coatimundis. The intelligent animals work in tandem to hunt squirrels and squirrel monkeys, and they are known to use tools to open up oyster shells or to kill venomous snakes.

Spider Monkeys (Mono Araña)
Spider Monkeys are the most intelligent monkey species in Costa Rica. Their muscular, prehensile tail can support the animal's whole weight and with their long, slender arms they move gracefully through the canopy in search for fruits, seeds and leaves.
Spider monkeys are severely endangered in Costa Rica due to habitat loss and poaching: in order to get the baby monkeys, the adults are killed by the poachers.
On the Nicoya Peninsula spider monkeys are almost extinct and a re-introduction program in the Curu Wildlife Reserve has not been successful. Spider monkeys are extremely sensible and don't along with changes in their habitat.

Squirrel Monkeys (Mono Titi)
Many people will recognize the squirrel monkey as the pet monkey of Pippi Langstrumpf. The fourth, and smallest of Costa Rica's monkey species is not found on the Nicoya Peninsula. It inhabits the rainforests of the Central and Southern Pacific coastal areas, from Manuel Antonio to the Osa Peninsula. The monkey's small size, expressive face, and playful demeanor make it a joy to watch. They travel through the canopy in groups, feeding on fruit, flowers, leaves, insects, lizards and frogs.
There are two supspecies: the Black-Crowned Squirrel Monkey, which inhabits the forests of Southern Costa Rica, ranging into Western Panama, and the Grew-Crowned Squirrel Monkey, who is endemic to the area between Quepos and the Rio Terraba. Both subspecies are considered endangered.