The rock rat or dassie rat is found in western South Africa, Namibia and southwestern Angola. (Heinemann, 1975)
Rock rats are small mammals, ranging in size from 100 to 300 grams. They have flat skulls with short ears, long black facial whiskers, yellowish noses, and hypsodont cheekteeth. Their teeth include narrow incisors and total 20 in number, in the pattern 1:1; 0:0; 1:1; 3:3. Their feet and claws are narrow, the forepaws have 4 digits and the hindpaws have 5 digits. Rock dassies' fur grows in clusters of 3-5 hairs, creating a bristly appearance, but it is generally smooth and soft to the touch. Their bodies blend in with the rocks, the dorsal side having a greyish tawny color and the ventral side grey or yellow. They also have incredibly flexible axial skeletons, allowing them to slip through narrow rock cracks for protection and shelter. With their short legs and squat build, these mammals are more adapted to running rather than jumping and locomote by running over the rocks of their habitat. Testes in the males are semi-internal and generally inconspicuous. The nipples of female rock rats are lateral and high on level with the scapula, allowing young to nurse from the sides when hiding in crevices. (Heinemann, 1975; Nowak, 1997; Shortridge, 1934)
- Sexual Dimorphism
- sexes alike
- Range mass
- 100 to 300 g
- 3.52 to 10.57 oz
- Range length
- 27 to 38 cm
- 10.63 to 14.96 in
Relatively little is known regarding the mating systems of.
Mating takes place in early summer, during the months of November and December. This breeding season appears to be fixed, and may be related either to the onset of the rainy season or it may be endogenous to the animals. (Coetzee, 2002; Coetzee, 2002; Heinemann, 1975; Nowak, 1997; Shortridge, 1934)
Females give birth to 1-3 young in late December or early January after a gestation period of about three months, and the young are precocial, rather large, and covered with hair. Young rock rats begin to eat solid food at around 14 days, weaning about one week later. (Coetzee, 2002; Heinemann, 1975; Coetzee, 2002; Heinemann, 1975)reach adulthood near the age of nine months.
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- Rock rats breed once yearly, in the summer months.
- Breeding season
- Mating occurs in November or December.
- Range number of offspring
- 1 to 3
- Average number of offspring
- Average gestation period
- 3 months
- Average weaning age
- 21 days
- Average time to independence
- 9 months
Little is known regarding the parental investment of.
The lifespan ofis unknown.
Dassie rats living in rocky areas usually emerge from their small crevices in the morning and late afternoon to forage and bask in the sun. Occasionally they also seek food after sunset, especially when there is a bright moon. They move across their rocky habitats by running and often jumping, spreading out and flattening their bodies in the manner of flying squirrels. Seeking food on the ground or in bushes, they travel alone or in pairs. Researchers who have been able to observe rock rats find that they are a playful species and sometimes frolick among plant stems. When disturbed they quickly dart into the safety of thin crevices and issue a warning call to other members of the species. (Heinemann, 1975; Nowak, 1997)
In one study, 15 individuals were recorded in a 6 hectacre area. Rock hyraxes, Procavia capensis, another small herbivorous mammal, compete with rock rats for shelter. In areas where these two species overlap, are restricted to smaller crevices where Procavia capensis cannot fit. (George and Crowther, 1981; George and Crowther, 1981; Nowak, 1997)
Communication and Perception
Little is known about communication among (Nowak, 1997), although they have been observed to emit a single whistling note as a warning signal to other rock rats when a predator is sighted.
- Communication Channels
- Plant Foods
- seeds, grains, and nuts
Known predators of dassie rats include numerous birds of prey, although particular species are not mentioned in current literature. To avoid aerial predators, rock rats often forage beneath rocky overhangs, out of view from birds above them. They are also protectively colored, blending in well with their rocky surroundings. (Heinemann, 1975; Nowak, 1997; Shortridge, 1934)
- Anti-predator Adaptations
- Known Predators
- birds (Aves)
As mentioned, (Shortridge, 1934)are prey for aerial predators. They are also seed predators, and possibly seed dispersers.
- Ecosystem Impact
- disperses seeds
- Acanthoxyurus shortridgei monnig
- Heteroxynema cafer
Economic Importance for Humans: Positive
The economic importance ofis unknown.
Economic Importance for Humans: Negative
The economic importance ofis unknown.
Rock dassies are not currently considered endangered, threatened or vulnerable.
Matthew Wund (editor), University of Michigan-Ann Arbor.
Kari Santoro (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
uses sound to communicate
- 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.
uses smells or other chemicals to communicate
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.
- desert or dunes
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
- active during the day, 2. lasting for one day.
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.
an animal that mainly eats leaves.
An animal that eats mainly plants or parts of plants.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
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).
Living on the ground.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
Coetzee, C. 2002. The distribution and breeding seasons of the dassie-rat, Petromus typicus. Folia Zoologica, 51 (Supplement 1): 23-25.
George, W., G. Crowther. 1981. Space partitioning between two small mammals in a rocky desert. Biological Journal of the Linnean Society, 15 (3): 195-200.
Heinemann, D. 1975. Old World Porcupines, Mole Rats, Rock Rats and African Cane Rats. Pp. 419-426 in B Grzimek, ed. Grzimek's Animal Life Encyclopedia, Vol. 11, 2 Edition. New York: Van Nostrand Reinhold Company.
Hugot, J. 1983. 2 Oxyurid parasites of Petromus typicus, an archaic South African rodent. Bulletin du Museum National D'Histoire Naturelle Section a Zoologie Biologie et Ecologie Animales, 5(1): 187-200.
Nowak, R. 1997. "Petromus typicus" (On-line). Walker's Mammals of the World. Accessed March 08, 2004 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world/rodentia/rodentia.petromuridae.petromus.html.
Shortridge, G. 1934. The Mammals of Southwestern Africa. London: William Heinemann Ltd..
Wilson, D., D. Reeder. 1993. Mammal Species of the World: A Taxonomic and Geographic Reference. Washington and London: Smithsonian Institution Press.