Class: Mammalia

Costa Rica is home to about 225 species of mammals, roughly six percent of the world's species. Seven of these are endemic to Costa Rica and exist nowhere else in the world. It is one of the few countries in America that retains the same number of mammal species today as it did when Spanish colonizers arrived five hundred years ago.

Twenty-one of our mammal species reach the southern limit of their range in Costa Rica and twenty-seven others reach their northern limits here. Despite the rich diversity, mammal encounters are relatively rare and usually ephemeral events.

As Ken Miyata and Adrian Forsyth write in their wonderful publication Tropical Nature:

"A naturalist's first visit to a tropical rainforest can be both an exhilarating and disappointing experience; the richness of the vegetation may overwhelm the senses at first, but sooner or later the apparent scarcity of animal or insect life will begin to raise questions."

Even the richest rainforest may only have an average of 14 mammal species. One reason mammal diversity in Costa Rican forests may at times seem dismal is that 109 of Costa Rica's 225 mammals are bats.

Bats are solely nocturnal and are usually only observed making speedy flybys overhead or not observed at all. Even when seen up close, many bats can only be identified by experts and then only by handling the animals.

Apart from bats, about three fourth of the remaining Costa Rican mammals are either partially or entirely nocturnal and rarely seen by travelers. Only about thirty Costa Rican mammals are active during the day and even these are sometimes elusive and shy.

About 142 mammal species have been observed on the Osa Peninsula. That amounts to about 63 percent of all Costa Rican mammal species. Common mammal species we encounter on the Night Tour include: Northern Raccoons, Crab-eating Raccoons, Mexican Mouse Opossums, Gray Four-eyed Opossums, Nine-banded Armadillos, Spiny Rats, Vesper Rats, Pacas, Tamandua Anteaters, Three-toed Sloths, Two-toed Sloths, Common Opossums, Woolly Opossums, Kinkajous, Striped Hog-nosed Skunks, Mexican Hairy Porcupines as well as several Bat species.

More elusive, and incredibly lucky, mammal encounters we have had on The Night Tour include: Ocelots, Margay, Pumas, and Tapirs. This page and the links on the right feature several common nocturnal mammal species represented in Drake Bay. All animals featured are wild individuals and most were photographed while on the Night Tour.

Paca - Agouti paca

The Paca is Costa Rica's largest rodent and is a nocturnal denizen of Drake Bay. Regrettably, this is not the case throughout the country. Despite being rodents, their meat is highly prized by hunters and is considered the best bush meat in the country. They have been hunted to the brink of extinction and are no longer found in many areas. Over the last few years we have seen this species making a comeback in Drake Bay and we commonly see them on the Night Tour.

Pacas are closely related to Agoutis but are strictly nocturnal. They spend their days sleeping in burrows, which have one main entrance and one or more escape routes. The Pacas stuff their escape routes, locally known as uzus, with leaves. If a predator enters the den, the Paca will burst through the leaves covering their escape route and flee to safety. Dens may be up 9 meters long and are usually dug into the side of a bank.

In areas where they are not persecuted, they are often quite tame and have no fear of people. On many occasions during the Night Tour we have had Pacas walk onto the trail from the bushes and head right towards the group! When startled, they run a short distance into the vegetation and stand perfectly still. Unfortunately, this strategy does not work well against hunters with dogs, lights, and guns.

Pacas mostly feed on seeds and fruit. They live in monogamous pairs throughout the year, but usually sleep in separate dens and forage solitarily. Breeding takes place year round and females normally give birth to a single offspring. Pacas have been known to live up to 16 years in captivity and range from southeastern Mexico to northern Paraguay.

Striped Hog-nosed Skunk - Conepatus semistriatus

Perhaps the most feared mammal to be found in Drake Bay's rainforests is the Striped Hog-nosed Skunk. An encounter with the wrong end of this animal is an unforgettable event. Hog-nosed Skunks, like other skunks, posses incredibly potent scent glands near their anus. If threatened they can spray an incredibly fowl smelling liquid at a perceived threat for a distance of about three meters.

The substance burns if it makes contact with the skin and may cause temporary blindness if it reaches the eyes. Even if no contact is made, the stench is so overpowering it immediately causes teary eyes, runny nose, and nausea. Hog-nosed Skunks are generally very docile, peaceful animals, though, and do not spray unless provoked. When angry, they will generally loudly stomp their foot on the ground as a warning.

Striped Hog-nosed Skunks differ from their cousins by their very long nose. They are often seen sniffing along the ground and digging with their long, sharp claws for insects, worms, and small vertebrates that make their home in the ground. They also forage for fruit and they seem to love coconut, as can be seen in the photograph above. In South America, Hog-nosed Skunks are immune to Pit Viper venom, and these snakes may also make up part of Costa Rican skunk's diet.

Females normally give birth to four or five kits and they may live as long as six years. Striped Hog-nosed Skunks range from Mexico to western Peru and eastern Brazil.

Vesper Rat - Nyctomys sumichrasti

Vesper Rats are perhaps the loveliest rats found throughout Costa Rica's forests. They are almost completely arboreal and move quickly and gracefully through the vegetation. The first toe on their feet is thumb-like and highly adapted to gripping twigs as they climb.

Because they are nocturnal, we often encounter them on The Night Tour. These little rodents tend to freeze when caught in a flashlight's beam, as is evident in the picture on the right.

These rodents feed on seeds, fruits and insects and range from southern Mexico to Panama.  They may live more than five years in captivity.

Vesper Rats very are similar in appearance to Mexican Mouse Opossums, but are much more commonly seen than the Mouse Opossum.

Mexican Mouse Opossum - Marmosa mexicana

Perhaps the only opossum in Costa Rica that rivals the Mexican Mouse Opossum's good looks is the Central American Woolly Opossum. This tiny marsupial is simply adorable.

Although similar to the Vesper Rat, Mexican Mouse Opossums have some distinctive identifying features. The easiest way to distinguish the two is by their tail. The Vesper Rat has a hairy tail, while the Mexican Mouse Opossum has a naked, fully prehensile tail. Mouse Opossums also have a dark mask around their eyes.

Mexican Mouse Opossums are quite rare to see in the wild, so our encounters are always prized ones. Their frequent presence in the stomach contents of Spectacled Owls (Pulsatrix perspicillata) at La Selva Biological Station suggests their numbers are greater than previously thought.

Adult Mexican Mouse Opossums are generally solitary and seldom seen together. Little is known about their social structure. Adults measure between 26 and 39 centimeters with a tail that is nearly as long as their body. They generally nest in trees, underneath logs, in dense bushes, tall grass, abandoned bird nests, or underground burrows.

Their diet is mostly made up of insects and fruit, but they may also eat lizards, bird eggs and small rodents. We found one individual inside our house feasting on a banana and they have been discovered stowed away in bunches of bananas as far away as New York City!

After mating, females are only pregnant for about two weeks. They may give birth to up to 13 larvae. Unlike many other marsupials, Mexican Mouse Opossums do not have pouches.

At birth, newborns crawl to the mother's mammary glands and attach themselves to one of the nipples. Should they fall off, the young opossums will cry out to their mother. She will pull the lost baby toward her belly until it reattaches to her teat. The young opossums travel on the mother's back or tail once they are old enough. If any of the young should die the mother will eat their remains.

Mexican Mouse Opossums range from southern Mexico to Panama.

White-nosed Coati - Nasua narica

Coatis are some of Costa Rica's most frequently observed mammals. Large groups, of up to 40 individuals, may  be observed making their way through the forest. Although they are active during the day, we often  see lone males at fruiting Malay Apple, Mango, and Breadfruit trees during The Night Tour.Al

Packs are made up of females and immature individuals. Male Coatis are solitary and are only allowed near the pack during their breeding season. At this time, the male is accepted by the females and will mate with each member of the group. Soon afterwards he will be expelled from the group, possibly because males are known to kill the newborns.

Pregnant females will break away from the pack about three to four weeks before giving birth. They usually make a leafy nest in a palm tree or a tree crevice. Females give birth to two to six young and they will remain in the nest until they are about four weeks old. Once they reach about six weeks of age, the pups and their mother will rejoin the pack. We encountered the pregnant female pictured above several nights on the Night Tour as she prepared her nest in a tree.

Coatis are omnivores and have a varied diet consisting of insects, frogs, lizards, small vertebrates, crabs, and fruit. They range from the southern United States, through Mexico, Central America and into western Colombia and Ecuador. Life expectancy for Coatis is about 14 years.

Enjoy our individual mammal pages by following the links on the upper right hand side of the page!

References:

Alonso-Mejia, A. & Medellin R.  1992  "Marmosa mexicana"  The American Society of Mammologists

Beletsky, L.  2005  Travellers' Wildlife Guides Costa Rica  Interlink Publishing

Emmons, L.  1990  Neotropical Rainforest Mammals  University of Chicago Press

Fogden, M. & P.  2001  Vida Silvestre de los Parques Nacionales y Reservas de Costa Rica  Editorial Heliconia, Fundacion Neotropica

Forsyth, A. & Miyata K.  1984  Tropical Nature  Touchstone / Simon & Schuster

Henderson, C.  2002  Field Guide to the Wildlife of Costa Rica  University of Texas Press

Janzen, D.  1983  Costa Rican Natural History  University of Chicago Press

Marceau, J. 2001. "Nasua narica" (On-line), Animal Diversity Web. Accessed January 08, 2009 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Nasua_narica.html 

Wainwright, M.  2002  The Natural History of Costa Rican Mammals  Zona Tropical

http://www.nhptv.org/NATUREWORKS/coati.htm

Weinstein, B. 1999. "Marmosa mexicana" (On-line), Animal Diversity Web. Accessed May 08, 2009 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Marmosa_mexicana.html