Crested rats are large rodents, ranging from 255 to 360 mm in head and body length. The tail adds another 140 to 215 mm, and these rodents weigh 590 to 920 grams. Females are generally larger than males. Crested rats are stockily built, with short snouts, broad heads, short legs, and wide feet. They have short ears. Their fur is long, thick, and fine-textured, except for a middorsal crest of coarse hairs that can be erected. Flanking the crest are prominant rows of scent glands. When it has its crest raised, a crested rat resembles a miniature porcupine. The coat is boldly patterned with black and white (or brown and white) stripes or patches. The underparts are gray to black, and the feet are black. The tail is short and bushy, and the soles of the feet are hairless. Crested rats have semi-opposable big toes, making them well-suited to their arboreal lifestyle.
The dental formula of crested rats is 1/1, 0/0, 0/0, 3/3 = 16. The incisors are smooth and orthodont, and the molars are rooted and cuspidate. Each zygomatic plate bears a prominant tubercle where the superficial masseter attaches. Crested rats have long incisive foramina, which extend back beyond the anterior margins of the molar rows. They also have a long, wide mesopterygoid fossa that extends between the third molars. There are small sphenopalatine vacuities, and a wide region of the squamosal separates the foramen ovale and masticatory foramen. The paroccipital processes are long and thick. The tympanic bullae are medium-sized, and there is an accessory tympanum. The malleus is of parallel construction, and a small orbicularis apophysis is present. (Carleton and Musser, 1984; Nowak, 1999)
The mating system of crested rats has not been reported.
Little information is available on reproduction in crested rats. All that is known is that litter sizes range from one to three young, and that females nurse their young for about 40 days. (Carleton and Musser, 1984; Nowak, 1999)
Young crested rats are relatively precocial; they are covered with hair at birth and grow quickly. Female crested rats nurse their young for about 40 days. No other information is available on the investment that these rodents make in their offspring. (Kingdon, 1974; Nowak, 1999)
Crested rats are arboreal; they climb with slow and deliberate movements. When climbing downward, they descend forefeet-first. They rest in hollow trees, fallen logs, burrows, or among boulders during the day, and come out to forage at night. Usually they are observed singly, but sometimes they are seen in pairs or in small groups consisting of a mother and her offspring. (Carleton and Musser, 1984; Kingdon, 1974)
Crested rats most likely perceive visual, auditory, tactile, and chemical signals, as do most rodents, but no information is available on the relative acuteness of these senses. These rodents are known to make peculiar hissing and growling noises. (Carleton and Musser, 1984)
These rodents have several unique adaptations for avoiding predation. Each crested rat possesses a row of erectile hairs lined by scent glands in a strip down the back. Each hair resembles a tiny sponge; when laid flat, it soaks up scent from the adjacent gland (Stoddart 1979). When the animal feels threatened, it raises the crest, diffusing its foul scent into the air, making itself look larger, and exposing large, aposematic white patches. In addition, some have suggested that the raised crest is meant to make the animal look like a porcupine, or that the glands or saliva of crested rats contain toxins. The latter has been backed up by reports of dogs foaming at the mouth and dying after attacking crested rats. Finally, the extra roofing of bone in the crested rat skull probably protects the brain and orbits from damage should a predator attack the head.
There are no known positive effects of crested rats on humans.
If they truly are toxic, crested rats could pose a hazard to humans or domestic dogs who kill and eat them. Also, they harbor fleas that carry plague. (Kingdon, 1974)
Tanya Dewey (editor), Animal Diversity Web.
Allison Poor (author), University of Michigan-Ann Arbor.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
uses sound to communicate
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
Referring to an animal that lives in trees; tree-climbing.
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
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.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
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).
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.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
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.
young are relatively well-developed when born
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Jansa, S., M. Weksler. 2004. Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences. Molecular Phylogenetics and Evolution, 31: 256-276.
Kingdon, J. 1974. East African Mammals: An Atlas of Evolution in Africa. Chicago: The University of Chicago Press.
Lavocat, R. 1973. Les rongeurs du Miocene d'Afrique Orientale. Memoires et Travaux de l'Ecole Pratique des Hautes Etudes, Institut de Montpellier, 1: 1-284.
Musser, G., M. Carleton. 2005. Superfamily Muroidea. D Wilson, D Reeder, eds. Mammal Species of the World. Baltimore and London: The Johns Hopkins University Press.
Nowak, R. 1999. Walker's Mammals of the World, vol. II. Baltimore and London: The Johns Hopkins University Press.
Stoddart, D. 1979. A specialized scent-releasing hair in the crested rat Lophiomys imhausi. Journal of Zoology, 189(4): 551-553.