Geographic Range
White-tailed rats,
Brachytarsomys albicauda
, can be found in eastern Madagascar from Marojejy (northeast) to Andringitra Massif
(southeast). This is a long narrow strip of land stretching from north to south which
has patches of rainforest. This is considered only the extent of their potential range,
due to the rarity of human encounters with these rats. They have been confirmed at
various locations in this range but not everywhere in it.
- Other Geographic Terms
- island endemic
Habitat
White-tailed rats have strong, sharp, curved claws. This characteristic and many others
indicate a high degree of specialization for arboreal life. that parallels the way
it nests in tree holes. They live in tropical forested areas in Madagascar. They nest
in tree holes, some have been observed in holes near the base of trees, most have
been observed within 2.5 m of the ground.
- Habitat Regions
- tropical
- terrestrial
- Terrestrial Biomes
- rainforest
Physical Description
There are two species in the genus
Brachytarsomys
,
B. albicauda
is the smaller of the two. Other than size,
B. albicauda
is distinguished from its cousin,
Brachytarsomys villosa
(Hairy-tailed antsangys) by its nearly furless tail. Though smaller than
B. villosa
, white-tailed rats are up to 50 cm long. They are easily identifiable by the white
tip on the tail, which averages 230 mm long. White-tailed rats are covered in a thick
coat of brownish-grey fur with a white underside. They have short snouts, giving the
face a blunt look.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
Reproduction
Virtually nothing is known about the reproductive ecology of
B. albicauda
or its cousin
B. villosa
. However, observations suggest they are monogamous.
- Mating System
- monogamous
Though there is little information available on the mating behavior of white-tailed
rats, it is known that they can have litters of at least 6 in the wild. A female of
this species was captured in late October with 6 well-formed embryos. Similarly, individuals
held in captivity produced litters of 6 young.
Unfortunately no other information about the offspring is reported
- Key Reproductive Features
- iteroparous
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
Little is known about parental care in white-tailed rats. Observations suggest males
may remain nearby after offspring are born and defend the nest while the female takes
care of young.
- Parental Investment
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- male
- female
-
provisioning
Lifespan/Longevity
The natural lifespan of B. albicauda is unknown. The lifespan in captivity has not been published.
Behavior
White-tailed rats are nocturnal and arboreal. It is assumed that they spend very little
time on the ground. They have specific adaptations that indicate a primarily arboreal
lifestyle. For example, they have an elongated fifth digit on the hind feet for better
gripping and an unusually long and flexible tail for greater balance. Nest cavities
are within hollowed portions of standing tree trunks and these rats travel along branches
to reach foraging areas without having to move across the ground. If white-tailed
rats are disturbed while on the nest, they will often appear at the entrance and chatter,
perhaps to scare away the disturber. This may indicate that they are territorial or
protective of young. Little else is documented about behavior.
Home Range
There is little information about the home range of
B. albicauda
. It is assumed that individuals stay very close to their nesting area.
Communication and Perception
Due to its nocturnal and arboreal nature, there have been few observations of white-tailed
rat communication behaviors. Like most nocturnal mammals, olfaction is likely to be
an important way of sensing the environment.
- Communication Channels
- acoustic
Food Habits
White-tailed rats are generally described as frugivorous. According to some, their
craniodental characteristics would be better suited for a leaf-eating (folivorous)
diet. They have short rostra, broad zygomatic arches, relatively wide incisors and
a long row of molars that have ridged masticatory surfaces. When offered an assortment
of leaves in captivity, white-tailed rats refused to eat them, preferring only fruit.
They may also eat seeds.
- Plant Foods
- seeds, grains, and nuts
- fruit
Predation
No information on predation of
B. albicauda
is available. Their nocturnality is an anti-predator adaptation and their brown coloration
serves as camouflage.
- Anti-predator Adaptations
- cryptic
Ecosystem Roles
No information on the ecological role of white-tailed rats is available. However, they may play a role in seed dispersal through their frugivorous habits.
- Ecosystem Impact
- disperses seeds
Economic Importance for Humans: Positive
White-tailed rats are hunted by local people who consider them as tasty as
lemurs
.
- Positive Impacts
- food
Economic Importance for Humans: Negative
There are no known adverse effects of B. albicauda on humans.
Conservation Status
White-tailed rats do not appear to be endangered. The IUCN redlist recognizes them
as "least concern." However, continuing human-induced habitat changes may impact populations
of white-tailed rats negatively.
Other Comments
The subfamily
Nesomyinae
is diverse, with 9 known genera (including
Brachytarsomys
) and endemic to the island of Madagascar. This degree of endemicity is typical of
Madagascar. It is unfortunate that so little is known about many of its native species.
The forests of Madagascar continue to shrink due to human destruction and every day
the diversity of the island is reduced.
Additional Links
Contributors
Scott Birkinshaw (author), University of Oregon, Stephen Frost (editor, instructor), University of Oregon, Tanya Dewey (editor), Animal Diversity Web.
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- island endemic
-
animals that live only on an island or set of islands.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- rainforest
-
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- monogamous
-
Having one mate at a time.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- arboreal
-
Referring to an animal that lives in trees; tree-climbing.
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- acoustic
-
uses sound to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- cryptic
-
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
- food
-
A substance that provides both nutrients and energy to a living thing.
- herbivore
-
An animal that eats mainly plants or parts of plants.
- frugivore
-
an animal that mainly eats fruit
References
Baillie, J. 2006. "Brachytarsomys albicauda" (On-line). IUCN Red List of Threatened Species. Accessed January 26, 2009 at http://www.iucnredlist.org/details/2991 .
Carleton, M., S. Goodman. 2003. Rodentia: Brachytarsomys, White-Tailed Tree Rats, Anstangy. Pp. 1368-1370 in The Natural History of Madagascar . Chicago: The University of Chicago Press.
Garbutt, N. 2007. Mammals of Madagascar . New Haven, Connecticut: Yale University Press.
Miljutin, L. 2008. Probability of competition between introduced and native rodents in Madagascar: An estimation based on morphological traits.. Estonian Journal of Ecology , 57: 133-–152. Accessed February 15, 2009 at http://kirj.ee/public/Ecology/2008/issue_2/ecol-2008-2-133-152.pdf .
Nowak, R. 1991. Walker's Mammals of the World . Baltimore: The John Hopkins University Press.
1975. The Cricetid Rodents. Pp. 318-319 in Grzimek's Animal Life Encyclopedia , Vol. 11, 2nd Edition. New York: Van Nostrand Reinhold Company.