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Brachytarsomys albicaudawhite-tailed rat

By Scott Birkinshaw

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. (Baillie, 2006; Garbutt, 2007)

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. (Baillie, 2006; Miljutin, 2008)

  • Range elevation
    450 to 1600 m
    1476.38 to 5249.34 ft

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. (Garbutt, 2007)

  • Range mass
    175 to 285 g
    6.17 to 10.04 oz
  • Average mass
    200-220 g
    oz
  • Range length
    410 to 500 mm
    16.14 to 19.69 in

Reproduction

Virtually nothing is known about the reproductive ecology of B. albicauda or its cousin B. villosa. However, observations suggest they are monogamous. (Carleton and Goodman, 2003)

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 (Carleton and Goodman, 2003)

  • Average number of offspring
    6

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. (Carleton and Goodman, 2003)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female

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. ("The Cricetid Rodents", 1975; Carleton and Goodman, 2003)

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. (Carleton and Goodman, 2003)

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. (Carleton and Goodman, 2003)

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. (Carleton and Goodman, 2003; Garbutt, 2007; Miljutin, 2008)

  • 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. (Nowak, 1991)

  • 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. (Miljutin, 2008)

  • 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. (Miljutin, 2008)

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. (Garbutt, 2007)

Contributors

Scott Birkinshaw (author), University of Oregon, Stephen Frost (editor, instructor), University of Oregon, Tanya Dewey (editor), Animal Diversity Web.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

arboreal

Referring to an animal that lives in trees; tree-climbing.

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.

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.

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.

food

A substance that provides both nutrients and energy to a living thing.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

island endemic

animals that live only on an island or set of islands.

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).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

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.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

1975. The Cricetid Rodents. Pp. 318-319 in B Grzimek, ed. Grzimek's Animal Life Encyclopedia, Vol. 11, 2nd Edition. New York: Van Nostrand Reinhold Company.

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 S Goodman, J Benstead, eds. 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.

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