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Thallomys paedulcusacacia rat

By Casey Ford

Geographic Range

Acacia rats are found in sub-Saharan Africa. They occur widely from the southern-most portion of Ethiopia, south to the east coast of South Africa. Their range extends to the west coast of Angola, through Zambia, Malawi and Zimbabwe. (Mills and Hes, 1997; Skinner and Chimimba, 2005)

Habitat

Thallomys paedulcus lives under the frayed bark of acacia tree trunks and branches, primarily Acacia xanthophloa and Acacia tortilis. It can sometimes seen near river beds. Its nests, which have been seen as high as 4 m from the ground, become highly visible during winter when foliage decreases. Acacia thorns provide optimal protection against predators. (Kingdon, 1984; Welton, 2004; de Graaff, 1978)

Physical Description

Acacia rats have a white venter and a grey-yellow dorsum. The fur is dense and soft and their ears are sparsely covered in hair. They have elongate hind- and forepaws, which possess long, curved claws. THeir brown tail is used to distinguish them from black-tailed tree rats. In addition, black-tailed tree rats have a more complete eye mask than acacia rats. Although they were once considered the same species, recent chromosomal evidence suggest they are distinct species. Acacia rats weigh between 63 and 100 g, with an average of 68 g. Weight can vary substantially in females, with weight increasing during lactation. Body length ranges from 12 to 16.3 cm, and the tail is often greater than or equal to the body, ranging from 13 to 21 cm. Sexual dimorphism has not been reported for this species. (Eccard, et al., 2004; Kingdon, 1984; Mills and Hes, 1997; Skinner and Chimimba, 2005; Welton, 2004; de Graaff, 1978)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    63 to 100 g
    2.22 to 3.52 oz
  • Average mass
    68 g
    2.40 oz
  • Range length
    12 to 16.3 cm
    4.72 to 6.42 in

Reproduction

There is little information on the mating system of Acacia rats. They give birth during the summer rainy season, when acacia foliage is present. Similar to many other murids, acacia rats are polygynandrous. Males expand their home ranges during breeding season, presumably in order to increase the likelihood of finding potential mates. (Eccard, et al., 2004)

There is little information available regarding the reproductive behavior of acacia rats, and that which is know was discovered via lab studies. They normally breeds every 3.5 months during summer (April through July) and litters consists of 2 to 5 pups, which weigh between 2.5 to 2.8 g t birth. Young are weaned 28 and 31 days old and reach sexual maturity at an average of 107 days. Pups begin walking after 15 days and incisors appear only after one day. Reproduction in acacia rats is thought to be similar to that of black-tailed tree rats. (Eccard, et al., 2004; Meester and Hallett, 1970; Meyer, et al., 2008; Mills and Hes, 1997)

  • Breeding interval
    Acacia rats breed once every 3.5 months.
  • Breeding season
    Acacia rats breed during the rainy season, which lasts from April through July.
  • Range number of offspring
    2 to 5
  • Average number of offspring
    2.7
  • Range weaning age
    28 to 31 days
  • Average age at sexual or reproductive maturity (female)
    107 days
  • Average age at sexual or reproductive maturity (male)
    107 days

There is no information available regarding parental care in wild acacia rats. In captivity, young attach to the nipple and nurse while the mother moves around the local environment. Pups stay with their parents until they reach reproductive maturity. (Meester and Hallett, 1970)

  • Parental Investment
  • female parental care
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

THe average lifespan of wild acacia rats has not been documented. Captive individuals live for an average of 3 years. (Gun, 2006)

  • Average lifespan
    Status: captivity
    3 years

Behavior

Little is known of the general behavior of acacia rats. They are arboreal and nocturnal, with nightly activities beginning prior to dusk. They construct nests out of leaves, grass, and small twigs. They burrow along Acacia tree root structures and use these burrows in the winter months in the event of brush fires. (Kingdon, 1984; Mills and Hes, 1997; Skinner and Chimimba, 2005)

  • Range territory size
    10000 to 100000 m^2

Home Range

Home range size varies in relation to sex. Female home ranges are about 10,000 m^2. Male home ranges are about 100,000 m^2 and sometimes overlapping into the range of another male. Males expand their home range during breeding season, likely increasing their chances of finding potential mates. (Eccard, et al., 2004; Meyer, et al., 2008)

Communication and Perception

Little is known about communication and perception of acacia rats. They appear to be very shy and rarely leave their shelters. They primarily live in conspecific communities and use scent markings to demarcate territorial boundaries. (Welton, 2004)

Food Habits

Acacia rats are primarily granivorous, feeding on the seeds and foliage of acacia trees. They have been observed foraging on Acacia tortilis and Acacia erioloba. The leaves of shepherd’s trees and seeds of buffalo thorn are also considered an important part of their diet. Other primarily granivorous, they also consume the berries, grasses, roots, buds, and gum of acacias. Food is generally brought back to the nest preior to consumption. Inedible plant materials are often used in nest making. They may also consume carrion or invertebrates when available. (Kingdon, 1984; Skinner and Chimimba, 2005; de Graaff, 1978)

  • Animal Foods
  • carrion
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • seeds, grains, and nuts
  • sap or other plant fluids

Predation

Acacia rats inhabit the thickest and thorniest parts of Acacia trees, which is an extremely effective in predator avoidance. Their sandy pelage provides great camouflage and likely helps reduce predation risk. It is thought that owls are their primary predators, however, arboreal snakes (e.g., Dendroaspis spp.) are important predators as well. (Kingdon, 1984; de Graaff, 1978)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Thallomys paedulcus is prey for a number of vertebrate predators including owls and a variety of snakes. As an arboreal rodent, it fills a unique niche that is not exploited by many rodents. Parasites of this species include the flea species Xemonpsylla brasiliensis, a known vector of the plague (Yersinia pestis), and Echidnophaga gallinacea. (Kingdon, 1984; Linzey and Kesner, 1997)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Although Thallomys paedulcus is not often seen in the pet trade, they are occasionally sought for their attractive coloring. Compared to other rodents, they breed poorly in captivity, making them unsuitable for lab use. (Gun, 2006; Welton, 2004)

Economic Importance for Humans: Negative

Acacia rats are possible vectors for the plague (Yersinia pestes). There are no other known adverse effects of acacia rats on humans. (Welton, 2004)

  • Negative Impacts
  • injures humans
    • carries human disease

Conservation Status

Acacia rats are classified as a species of least concern on the IUCN's Red List of Threatened Species List. Although current population trends are unknown, they are thought to be widespread and locally abundant throughout their geographic range. Currently, there are no major threats to the long-term persistence of this species. (Linzey and Kesner, 1997)

Contributors

Casey Ford (author), Northern Michigan University, Mary Martin (editor), Northern Michigan University, John Berini (editor), Animal Diversity Web Staff.

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.

carrion

flesh of dead animals.

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.

female parental care

parental care is carried out by females

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

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).

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

omnivore

an animal that mainly eats all kinds of things, including plants and animals

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sexual

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

social

associates with others of its species; forms social groups.

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

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.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

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

Eccard, J., W. Jean, M. Wichmann, S. Huttunen, E. Eskelinen. 2006. Use of large Acacia trees by the cavity dwelling Black-tailed Tree Rat in the Southern Kalahari.. Journal of Arid Environments, 64/4: 604.

Eccard, J., J. Meyer, J. Sundell. 2004. Space Use, Circadian Activity Pattern, and Mating System of the Nocturnal Tree Rat Thallomys nigricauda. Journal of Mammalogy, 85/3: 240-245.

Gun, K. 2006. "Acacia Rats" (On-line). Thames Valley Rodents- Small Animal Encyclopedia. Accessed March 11, 2011 at http://abcexotics.webs.com/acaciarats.htm.

Kingdon, J. 1984. East African Mammals: An Atlas of Evolution in Africa. Chicago: University of Chicago Press.

Linzey, A., M. Kesner. 1997. Small mammals of a woodland-savannah ecosystem in Zimbabwe. I. Density and habitat occupancy patterns. Journal of Zoology, 243/1: 137-152.

Meester, J., A. Hallett. 1970.

  1. Notes on Early Postnatal Development in Certain Southern African Muridae and Cricetidae
. Journal of Mammalogy, 51/4: 703-711.

Meyer, J., A. Kohnen, R. Brandl. 2010. Genetic differentiation in an arboreal rodent from African savannas. African Journal of Ecology, 41/3: 831-836.

Meyer, J., D. Raudnitschka, J. Steinhauser, F. Jeltsch, R. Brandl. 2008. Biology and ecology of Thallomys nigricauda (Rodentia, Muridae) in the Thornveld savannah of South Africa.. Mammalian Biology, 73/2: 111.

Mills, M., L. Hes. 1997. The complete book of southern African mammals. Cape Town, South Africa: Struik Book Distributors.

Skinner, J., C. Chimimba. 2005. The Mammals of South Africa Subregion. Cambridge, UK: Cambridge University Press.

Welton, N. 2004. Rats, Mice, and Relatives III: Old World Rats and Mice (Murinae). Pp. 249-262 in M Hutchins, A Evans, J Jackson, eds. Grzimek's Animal Life Encyclopedia, Vol. 16, 2nd Edition. Detroit: Gale Virtual Reference Library. Accessed March 10, 2011 at http://ezpolson.nmu.edu:5749/ps/start.do?p=GVRL&u=lom_nmichu.

de Graaff, G. 1978. Notes on the Southern African black-tailed tree rat thallomys paedulcus (Sundevall, 1846) and its occurrence in the Kalahari Gemsbok National Park. Koedoe, 21/1: 181-190.

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