Lophiomyinaecrested rat

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Diversity

Lophiomyinae is an Old World cricetid subfamily containing just one genus and one species, Lophiomys imhausi, or crested rats. (Musser and Carleton, 2005)

Geographic Range

Crested rats are native to eastern Africa, including Sudan, Ethiopia, Somalia, Kenya, and Tanzania. (Carleton and Musser, 1984)

Habitat

Crested rats inhabit mountain forests and woodlands, as well as rocky slopes and ravines. They are generally found at high elevations, up to 3,300 meters. (Carleton and Musser, 1984; Nowak, 1999)

Physical Description

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)

  • Sexual Dimorphism
  • female larger

Reproduction

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)

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

Lifespan/Longevity

Crested rats may live almost eight years in captivity, but their lifespan in the wild has not been reported. (Nowak, 1999)

Behavior

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)

Communication and Perception

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)

Food Habits

Crested rats are herbivorous, eating leaves and tender young shoots. They will also eat insects and meat when kept in captivity. (Kingdon, 1974; Nowak, 1999)

Predation

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 have been no reports of a predator successfully attacking and eating a crested rat. (Carleton and Musser, 1984; Kingdon, 1974; Nowak, 1999; Stoddart, 1979)

Ecosystem Roles

Crested rats are primary consumers. They are parasitized by fleas, including Amphopsylla conversa. (Kingdon, 1974; Nowak, 1999)

Commensal/Parasitic Species
  • Amphopsylla conversa

Economic Importance for Humans: Positive

There are no known positive effects of crested rats on humans.

Economic Importance for Humans: Negative

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)

  • Negative Impacts
  • injures humans

Conservation Status

Lophiomys is not currently considered threatened by the IUCN, but it may nevertheless be rare and more research is needed into its habits and distribution. (Amori and Gippoliti, 2003)

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Allison Poor (author), University of Michigan-Ann Arbor.

Glossary

Ethiopian

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

World Map

acoustic

uses sound to communicate

aposematic

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.

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

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.

folivore

an animal that mainly eats leaves.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

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.

mountains

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.

nocturnal

active during the night

poisonous

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).

sedentary

remains in the same area

sexual

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

solitary

lives alone

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.

young precocial

young are relatively well-developed when born

References

Amori, G., S. Gippoliti. 2003. A higher-taxon approach to rodent conservation priorities for the 21st century. Animal Biodiversity and Conservation, 26(2): 1-18.

Carleton, M., G. Musser. 1984. Muroid rodents. Pp. 289-379 in S Anderson, J Jones Jr., eds. Orders and Families of Recent Mammals of the World. New York: John Wiley and Sons.

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.