Hedgehog, sugar glider, sto, short-tailed opossum, duprasi, squirrel, mouse, mice, rats, rabbit,
bunny, chinchilla, hamster, gerbil, rat, birds, guinea pig, degu, jird, dormouse, lemming, jerboa, prairie dog, chipmunk,
ferret, skunk, agouti, belgian hare, english lop
Species: M. domestica
Binomial Name: Monodelphis domestica
Common English Names
Grey Short-tailed Opossum, Brazilian Opossum, Brazilian Short-tailed Opossum, S.T.O and Rainforest Opossum
Members of the Genus, Monodelphis include a large group of American marsupials, consisting of at least 22 species. Although
they all bare close similarities, they are all unique and therefore have been broken down into 8 groups.
- Brevicaudata which has 5 species (including the S.T.O.)
- Adusta containing 4 species
- Dimidata with 2 species
- Theresa with 2 species
- There is also one other group that is being studied but has yet to be named.
In the wild due to overlap in territories hybrids are a natural occurrence.
Status in the wild
In their wild habitat this species is considered common and of least concern.
They are a tropical species that is native to South America. They are usually found living in dry rocky areas
at the edge of rainforests in Brazil, Bolivia and Paraguay. They are solitary animals who establish a relatively small territory
and often live out their lives in only 2 acres or less. Short-tailed Opossums are often described as being nocturnal but we
find that ours are a lot more active during the first few hours after twilight. We seldom notice much activity during the
midnight hours but occasionally we see them being active just before dawn, which makes me think that they are more of a crepuscular
species. They typically build their nests using leaves and twigs in rock crevices and in hollows of trees. They are also known
to venture into people’s dwellings and abandoned buildings. They are one of the few wild species that seem to benefit,
from the habitat disturbances that we humans cause. Many indigenous people welcome the S.T.O.s into their dwellings to help
keep insects and other types of pests under control.
Status in Captivity
During the 1980s, S.T.O.s were imported into North America to be used for scientific research in labs. Before
long a few hobbyists discovered how unique they were and what a wonderful disposition they had that it wasn’t long before
they made their way into the Pet Trade. During the 1990’s more people became fascinated with this unusual animal and
a select group of breeders started to promote them as pocket pets. In North America and Europe, Short-tailed Opossums are
still considered as a relatively new type of pet and are still considered rare in captivity but they are becoming increasingly
popular pets. While the demand for them as pets is steadily climbing, do to the scarcity of this unique species we feel that
it is very important to be extremely selective when placing them into pet homes. We prefer to sell them as pairs to Specialty
Pet Enthusiasts who have a keen interest in selective breeding.
As a result of selective breeding practices, new colour morphs are beginning to appear. New colour morphs
are a work in progress but now if you search hard enough, you’ll be able to find rosy breasted, pied and a few other
At a quick glance Short-tailed Opossums could be mistaken for a type of arboreal rat. Although their tail
is semi prehensile, to some people it might be described as almost rat like in appearance. Their tails are not as whip-like
as a rat’s tail and they use their tails in a number ways. Their tail can be used to carry nesting material back to
their dens or to help with balance when they are hunting prey on small branches. In the wild type variety, their fur is grey
to somewhat of a charcoal grey colour.
Short-tailed Opossum males are typically larger than their female counterparts. Body measuring in at 10-15cm
and their tail is an additional half the body length. Weight is typically around 90-155g. Females weigh around 80-100g. Short-tailed
Opossums are marsupials but unlike many marsupials all ‘new world’ marsupials lack the pouch. Instead of the security
of a pouch the babies attach themselves to a teat. Then the teat swells in their mouth, which helps them, to anchor themselves
to their mother’s belly. They remain holding on and attached until they can walk around and cling onto their mother
independently. They have excellent nocturnal eyesight, an acute sense of smell and large hairless ears that are capable of
hearing minute sounds.
When these senses are combined it makes them an ideal nighttime predator.
Males are typically larger than females and have a visible descended scrotum. Females have 13 teats.
In captivity they can live between 5-6 years. In the wild Short-tailed Opossums live on average 2 –
2.5 years. Though they are successful predators that prey on insects, and other small creatures, they are still considered
a prey species for many larger predators. Generally males tend to have a shorter life span than females simply because they
are more likely to be injured during mating. S.T.O.s are extremely territorial and don’t like the company of other members
of their own species. Even during their natural breeding season females will often attack their male suitors.
Short-tailed Opossums are omnivorous and opportunistic feeders. If it is alive and they can catch it, they’ll
eat it. If it is already dead they will consume it. They feed primarily on insects, small mammals, small lizards, amphibians,
crustaceans, eggs, birds, fruit, nectar, plant matter and terrestrial non-insect arthropods (worms). We feed ours a balanced
diet consisting of no grain highly palatable protein kibble, cheeses, eggs, chicken, shrimp and small bits of human grade
meats. All of the meat we feed is fully cooked and unseasoned. We do not feed live food and while many breeders still do feed
insects, baby birds and mice, we do not feel that it is necessary. Over the years we have fed live foods that when offered,
our S.T.O.s would consume readily. When we switched their diets to cooked meat we did not notice a difference in behaviour
but noticed that more of their babies thrived and reached maturity. Perhaps this is a coincidence? Perhaps the live insects
and animals somehow endangered the lives of the babies by injuring them while the mother was chasing them or perhaps the insects
and other species passed on harmful bacteria or viruses? Maybe we will never know why this change in mortality happened but
we are happy with the choice we made to switch to fully cooked animal protein. In addition to animal protein we feed a variety
of fruits and vegetables on a daily basis. Our S.T.O.s drink water from a water bottle and a water bowl. The benefit of the
water bottle is that the water stays cleaner longer and open water dishes provide a bit more humidity into the environment.
Our animals will use either types and both have their own advantages. No matter which water system you choose it is important
that fresh, clean water is available at all times. S.T.O.s do drink a lot of water.
Temperature and Humidity Requirements
Short-tailed Opossums are from tropical and sub-tropical semi-forested areas and clearings within the rainforests.
When we humans think of the rainforest, we naturally think hot but this is not always the case. When you live in the under-story
of a forest the temperature is more constant and because of the shade that trees provide, it is usually much cooler than in
open areas. An STO prefers to build their nest in dry places but the humidity in the air is almost always humid. Ideally,
Short-tailed Opossums are comfortable when kept around 20 –22 degrees Celsius or a bit higher and the humidity level
should be in the medium range (around 40% to 50%). Most often during the summer months providing extra humidity isn’t
required, unless you live in drier regions of the country. But during the colder winter months when forced heated air is used
to heat our homes the air is drier. Then we lightly mist our S.T.O cages, with R.O. water, every couple of days. Because we
use a humidifier, I am not entirely sure that they need the extra misting but ours sure do seem to enjoy it. When a mother
has babies attached to her, being that they lack a pouch, the babies are somewhat exposed and therefore rely on mom and the
external temperature to keep them warm. If mom has babies on board we recommend keeping the ambient room temperature at a
little higher than normal range (22-24 degrees Celsius).
Short-tailed Opossums are extremely anti-social with other members of their own species and must be kept housed
in separate cages. While they are solitary and territorial animals, they do develop strong bonds with their keepers. They
are best housed in an open-air cage with hamster like wire spacing. Some people choose aquariums or terrariums that are fitted
with a tank-topper. Always choose the biggest habitat that you can fit into your space and make sure it is of a size that
you can comfortably manage at cleaning time. Be sure it is large enough to add lots of things for your S.T.O. to climb on
and lots of toys to explore. They all require an exercise wheel, a water bowl and a sleeping hut for the pets to nest in and
clean fresh nesting material. Trying to mimic their natural environment would definitely add to the animal’s health
and happiness. Always be sure to add things for them to investigate and to help keep them stimulated. Make sure that whatever
you give to your pet is safe. When you choose to use bedding instead of a cage liner; aspen, hay or ‘Carefresh’
all appear okay to use. While not always practical for many pet owners, some people use cage liners. STO’s are very
clean animals. Most of our S.T.O.s are potty trained and they have done that on their own.
Behaviour in Captivity
I can not stress enough that Short-tailed Opossums must be housed separately. When frightened they have a
tendency to display aggression by opening their mouths wide while making a clicking/hissing sound. This can seem rather intimidating
but most of it is bluff. I have never been bitten by an S.T.O. in the past 15 years. With constant interaction especially
when started at a young age, Short-tailed Opossums will bond with their keepers. We find that males tend to be more relaxed
than females and seem a little calmer. S.T.O.s are not aggressive chewers. They tend to be more of a gatherer and are constantly
picking things up by using their tails to carry things back to their nest.
Short-tailed Opossums need very little in the aspect of grooming. Proper husbandry and keeping temperature
and humidity levels at adequate levels should be sufficient. They are self-groomers and mothers will clean her young until
they are ready to be weaned.
Keeping Short-tailed Opossums with other pets
Never leave your S.T.O. unattended with other pets. Not many species of small animals have any type of advanced
natural defense strategies and STOs don’t stand much of a chance when attacked by a larger animal. Normally whenever
they are frightened the Short-tailed Opossums will use bluff, play dead or attempt to flee. They are small enough to become
prey for predatory type animals such as a dog, a cat, ferret, snake or medium size lizards etc.. Yet they are large enough
to be considered a predator animal and will prey upon other small pets such as mice, hamsters, birds, small snakes and lizards
etc. AGAIN …Never leave your S.T.O. unattended with other pets!
Breeding (Not for the amateur)
Breeding age females are polyestrous and induced ovulators. Since they are solitary by nature sometimes mating can be challenging.
When the male encounters a female he’ll sniff to see if she is receptive. They will engage in a ritualistic somewhat
violent dance of grabbing, sniffing, biting and licking. The male will eventually immobilize the female and begin mating.
It is not uncommon for S.T.O.s to become wounded during mating and sometimes the male risks loosing his life.
Males and females can reproduce at 5-7 months of age. They are seasonal breeders in the wild. Breeding season naturally
is during the spring and summer months (September – December) and can have two litters per season. In captivity they
can breed all year round. They can successfully care for 1 – 13 babies per litter, with the average litter being 7 –
9. Short-tails have thirteen teats so a successful rearing of 10+ isn’t uncommon but if 15 babies were born it is only
possible for 13 to attach themselves to a teat. The remaining 2 will perish and usually be eaten by the mother. They start
to wean at 3-4 weeks of age and will continue either hanging onto mom or following their mother around for an additional month
or more. When they reach weaning age they must be seperated.
In captive breeding programs a variety of colour morphs are starting to become established. Rosy, pied, darker / lighter
shades of grey and ivory are appearing regularly.
Ailments and Veterinary Requirements
All animals can benefit from annual visits to a qualified Veterinarian. Be sure that your vet is knowledgeable about Short-tailed
Opossums. The most common reasons requiring Veterinary care is injuries sustained through fights (normally at breeding time)
and damaged ears, which is usually a result of low humidity.
Costs to consider
The costs to set up a suitable habitat can vary but you can expect to pay in the neighborhood of $200.00 or more for a
reasonably decent setup (including the cage, a few toys, wheels, sleeping dens, etc.). An S.T.O. will likely cost around $175.00
and up, depending on colour, sexes, etc.
Where to purchase
Ideally,exotic pets should be purchased from "Specialist Breeders". If you are planning to breed. buying your breeding
stock from an experienced breeder will likely be worth the investment. Most breeders are proud of their own animals and enjoy
talking about them, which can be a great source of information. Not all Pet Stores are bad, nor are all of the people who
work in them. Actually some very knowledgeable people work in them. Unfortunately, they are paid to sell and it is a retail
business. That being said you’ll need to decide for yourself whether or not you feel comfortable buying pets from them.
Sometimes it is better to shop around. Wherever you choose to purchase your pet from, as long as you have done all of your
research and you are comfortable with the people that you are dealing with, only then you will you be in the position to make
an educated decision.
Having to ‘re-home’ your pet
For some people having to make the decision to give up a pet may be one of the hardest things they will ever have to do.
It can be very emotional and stressful for the caregiver and the pet. If you find yourself in an emergency situation and need
to re-home your pet, try contacting the breeder to see if they can help. We believe that most ethical breeders will do their
best to help. Often, in the case of a real emergency, most conscientious breeders will offer to take back the animal. This
is a good habit that responsible breeders get into, not only does it prevent animals from ending up in shelters or sanctuaries
it also makes people think twice before abandoning them in the wild.
People contact us regularly to see if we can help them sell their pet. PLEASE NOTE …We will not help you sell
your pet! However if you ever find yourself in a position whereby you can no longer adequately care for your pet S.T.O.
or if you feel that your pet needs to be in a home with someone more experienced, you are free to call us. We do realize that
every situation is different but we will do our best to suggest a few options for you to consider before you decide to re-home
your pet. Occasionally, if we have the space and time, we will take in S.T.O.s that are in need of new homes. Just be aware
that if we do commit to taking in your pet, we will keep them for as long as it takes to find them a suitable home. We will
not keep them forever because we are breeders. We need to know the lineage and history on all of our animals in our breeding
program. We do have a special needs page on our site for people looking to adopt/purchase animals in need of rehoming. If
we can not personally accommodate another animal in our own home then we may be able to recommend someone who can.
Clubs, Associations and Breeder links
If you are an experienced specialist breeder or a legitimate specialty club and would like to add a reciprocal link to
our site please feel free to email us. Please note that we will not provide links to Rescue Organizations that are not open
to the public, unless we have the opportunity and time to personally inspect the "Rescue" organizations first. Sorry to all
of the people who truly dedicate their time to legitimate animal rescue, unfortunately too often people misrepresent themselves
pretending to be licit or scrupulous rescuers.