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.
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.
Miyata and Adrian Forsyth write in their wonderful publication
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
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 110
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
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.
mammal species have been observed on the Osa Peninsula. That amounts
to about 63 percent of all Costa Rican mammal species.
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,
Kinkajous, Striped Hog-nosed Skunks,
Mexican Hairy Porcupines as
well as several Bat species.
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.
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 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.
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
Skunk - Conepatus semistriatus
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.
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.
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 are also fond of different
fruits and coconuts.
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 Perúand eastern Brazil.
Vesper Rat -
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
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
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
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
Mexican Mouse Opossums range from southern Mexico to Panama.
Gray Four-eyed Opossum - Philander opossum
The Gray Four-eyed
Opossum is one of our most commonly encountered mammals on the tour.
They are called Four-eyed Opossums because of the conspicuous white
spots which are positioned above each eye.
small marsupials frequent creeks, rivers and swamps where they feed
on frogs and freshwater shrimp.
Other food items preferred by Four-eyed Opossums may include
lizards, bird eggs, fruit, nuts and nectar.
Female Gray Four-eyed Opossums have a well developed pouch where
they carry their young for about two and a half months.
Litters may number between two and seven larvae. After the young
opossums emerge from the pouch, they will remain in a nest created
by their mother and continue nursing for another two weeks.
Four-eyed Opossums reach sexual maturity at seven months of age and
usually only live for about two years. Their range extends from
southern Mexico to Paraguay and northern Argentina.
White-nosed Coati -
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.A
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.
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.
Their range spans from the southern United
States, through Mexico, Central America and into western Colombia
and Ecuador. Life expectancy for Coatis is about 14 years.
Crab-eating Raccoon -
Procyon cancrivorus and
Northern Raccoon - Procyon lotor
There are two species of Raccoon in Costa Rica and they both
make their home in Drake Bay. The Northern Raccoon ranges into North
America while the Crab-eating Raccoon ranges into South America.
Both Raccoon species look very similar and are difficult to
distinguish from a distance. The Crab-eating Raccoon is larger than
the Northern Raccoon.
Crab-eating Raccoons differ from Northern Raccoons because
the fur on their necks points towards the head, instead of towards
the tail like the fur on rest of the animal's back.
Also, the bands on their tails tend to be orange instead of
white and they tend not to have under fur.
Costa Rica and Panamá are the only two countries where the two
The word Raccoon is derived from the North American
indigenous word "arakun" meaning scratching hands.
Both species are very good climbers, but often forage on the
ground. They feed on crabs, mollusks, fish, frogs, small
vertebrates, insects, fruit and other food they may scavenge.
Raccoons are mainly solitary and nocturnal, but they are
sometimes active during the day.
Little is known about the natural history of Crab-eating
Raccoons but Northern Raccoons have been widely studied. With this
species, a female Raccoon will typically receive one male when in
heat and she allows him to mate and to accompany her for a few
weeks. The female will eventually drive the male away in order to
protect their her litter, since males are known to kill the young.
Gestation last 2 months and litters range from 1 to 7 cubs.
The cub siblings leave their mother at about 9 months old and they
may run together as a pack for a few months after leaving.
Nine-banded Armadillo -
There are two species of armadillo in Drake Bay: the
Northern Naked-tailed Armadillo (Cabassous centralis) and the
Nine-banded Long-nosed Armadillo (Dasypus novemcintus).The latter is pictured here.
Nine-banded long-nosed Armadillos are common and often encountered
in Drake Bay.They can be active at night or during the
day and usually forage slowly, with their snout pressed right to the
ground.Their keen sense of smell aids them in
detecting prey items living in the leaf litter or underground.In the tropics, Armadillos feed mostly on
ants and termites, as well as fallen fruit.
These animals have very poor eyesight and it is not uncommon for
them to walk right into a bewildered hiker’s feet.When startled, Nine-banded long-nosed
Armadillos will often jump straight up into the air and rush to
The reproductive cycle of Nine-banded Long-nosed Armadillos is
nothing short of amazing.After mating, females are able to control
the start of pregnancy by delaying the implantation of the
fertilized egg on the uterus wall.
Although this animal's gestation
period only lasts about 2 months, female Armadillos have stunned
researchers by giving birth up to 32 months after mating! When they
do give birth, it is exclusively to same sex identical quadruplets.
Hoffmann's Two-toed Sloth -
In Costa Rica's lowland rainforests Hoffmann's Two-toed
Sloths, Choloepus hoffmanni, are not so common to see. These animals are
mainly nocturnal and they forage high in the canopy. They are active
about 8 hours per day.
Although they are active for shorter periods than Three-toed Sloths,
Two-toed Sloths are more mobile. They change trees frequently and
are rarely found in the same tree on consecutive days.
Two-toed Sloths feed mainly on leaves but they supplement their
leafy diet with fruit, buds, flowers, insects, and even bird eggs
and small vertebrates.
Two-toed Sloths have an incredibly long gestation period, about 11.5
months. Baby sloths cling to their mother during the first 6 months
of their lives, never leaving her side.
Even after they are weaned, young sloths may remain close to their
mother for up to two years.They have been known to live up to 32 years
close inspection of the Two-toed Sloths in the two photographs
featured here will reveal a distinctive green tint on the fur.
Sloths have slits on each one of their hairs that serve as
compartments where algae grows.
has long been thought that the green tint afforded by the algae
helps sloths better blend into their canopy habitat. This theory
makes sense; after all having a green tint should help canopy
dwelling sloths conceal themselves in the treetops.
Recently, though, researchers have proposed that perhaps the algae
is providing sloths with an added benefit.
Scientists think that perhaps the Sloths are acquiring nitrogen from
the algae, which is something they do not obtain from their
primarily leafy diet.It is thought that the nitrogen is then
passed on to the Sloths through ingestion or by absorption through
The moths, which can be observed on the photo on the left, play a
role in this as well. It appears that the amount of algae growing on
the fur is directly correlated to the number of moths living on the
sloth. The algae thrives on the feces and decaying remains of the
moths, so the bigger the moth population, the more the algae grows.
This leads researchers to think that the Sloth's peculiar
habit of coming down to the ground to urinate and defecate could be
linked to this chain.
When the sloth defecates on the ground, moths and beetles
living on the sloth crawl down and lay their eggs on the feces. The
larvae develop there and eventually fly back into the treetops as
adults in search for another Sloth host.
The Sloths put themselves at considerable risk by travelling
all the way down to the ground to defecate, but in doing so they
provide these insects with a suitable place to lay their eggs and a
great place for their larvae to develop.
The insects insure the propagation of the algae on the
Sloth's fur and the algae provides the Sloth with an important
nutritional supplement. The complicated relationship between these
completely different creatures is so intertwined that Sloth Moths,
Cryptoses choloepis, have evolved to live exclusively in
the fur of Sloths and do not exist anywhere else in nature.
Mexican Hairy Porcupine - Sphiggurus mexicanus
The Mexican Hairy Porcupine is one of the most elusive
mammals in Drake Bay. So much so, that it is not listed as being on
the Osa Peninsula in many of the guide books. It took us many years
before we saw our first one and they are always a rare find around
They tend to be nocturnal and solitary and very little is
known about their natural history.
Technically Porcupines are rodents and they are the only
rodents in Costa Rica to have a prehensile tail. Porcupine's tails
are different from any other new world mammal in that the gripping
pad is located on top of the tail, rather than on the bottom.
When they grip with their tail it curls upward, as can be
observed in the photograph featured here.
The Porcupine's quills are this animals most prominent and
Although Porcupines cannot throw their quills, the quills do
provide Porcupines with protection from predators by breaking off
very easily and lodging into a would be predator's skin.
Each quill has a very sharp point and is covered with tiny
backward pointing scales. This makes them very difficult to remove
once they are lodged in the skin.
It is thought that the yellow quills also serve as
aposematic coloration, warning colors, to deter predators. Also,
when Porcupines are startled the quills stand vertically making them
look much larger than they actually are.
Despite their spiny armor, felines feed on porcupines by
flipping them onto their back where they lack quills.
Mexican Hairy Porcupines feed mainly on seeds, fruit,
leaves, flowers and flower buds. They enjoy Ficus spp., Cecropia
spp., and we often encounter them feeding on the fruit of
Below is a video of a Mexican Hairy Porcupine we recorded
during a Night Tour
Enjoy our individual mammal pages by following the links located at
top of the page on the
right hand side!
A. & Medellin R. 1992 "Marmosa mexicana"
The American Society of Mammologists
2005 Travellers' Wildlife Guides Costa Rica
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,
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