Reithrodon auritusbunny rat(Also: coney rat)

Geographic Range

Bunny rats (Reithrodon auritus), also commonly called rata conejo or coney rats, are found in the Patagonian region of Argentina, southern Chile, and parts of Uruguay.The type locality for Reithrodon auritus is on the south bank of the Rio de la plata in the southern pampas of Buenos Aires, Argentina. (Pardinas and Galliari, 2001; Wilson and Reeder, 1993)

Habitat

Reithrodon auritus is most commonly found in open habitats such as cultivated fields, pampas, stony hills, and sandy coasts. They inhabit a wide range of elevations, found sea level to 2170 meters elevation. Bunny rats live in burrows that they dig themselves or they make use of abandoned burrows made by other fossorial mammals. They also use natural cavities among rocks. (Nowak, 1999; Pardinas and Galliari, 2001)

  • Range elevation
    0 to 2170 m
    0.00 to 7119.42 ft

Physical Description

Bunny rats have thick, soft fur. The upper part is a mix of grayish and black hairs and the underside is whitish or grayish. An adult bunny rat has a total body length of 195 to 269 mm, tail length of 65 to 104 mm, up to 65% of body length. They have an average body mass of about 80 g and a resting metabolic rate of 0.4280 W. Some key physical features used to identify Reithrodon auritus are: they have two grooves on the enamel of the upper incisors, there is a reduction in size of the outer hind toes, the middle hind toes are webbed, and the ears are large, rounded, and covered with hair. (Nowak, 1999; Pardinas and Galliari, 2001)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    20.5 to 116 g
    0.72 to 4.09 oz
  • Average mass
    80 g
    2.82 oz
  • Range length
    21.5 to 30.5 cm
    8.46 to 12.01 in
  • Average basal metabolic rate
    0.4280 cm3.O2/g/hr
  • Average basal metabolic rate
    0.428 W
    AnAge

Reproduction

The mating system of bunny rats is not well understood. It is thought that males attempt to mate with as many receptive females as they can.

Bunny rats are reproductively active during the spring months. Reithrodon species have been found to breed throughout the year and the number of young varies considerably, from 1 to 8 with an average of 4.53. Females become sexually mature at about two months old, before reaching a body mass of 52g. Males take a little longer to reach sexual maturity; when their seminal vesicles are longer than 12mm which is around three months of age. (Nowak, 1999; Pardinas and Galliari, 2001)

  • Breeding season
    Breeding occurs primarily in the spring months.
  • Range number of offspring
    1 to 8
  • Average number of offspring
    4.53
  • Average number of offspring
    4.5
    AnAge
  • Average age at sexual or reproductive maturity (female)
    2 months
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    61 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    3 months

Females nurse and care for their young until they are weaned. They leave the young in their grass or fur-lined nests, providing little else in the way of protection. Males do not invest in the care of their young. (Pardinas and Galliari, 2001)

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

Lifespan/Longevity

The average lifespan of Reithrodon auritus in the wild is 3.7 months with a maximum longevity in the wild of about 15 months. One captive bunny rat lived for 5.5 years. Lifespan is limited by predation from owls. (Pardinas and Galliari, 2001)

  • Range lifespan
    Status: captivity
    5.5 (high) years
  • Average lifespan
    Status: wild
    3.7 months
  • Average lifespan
    Status: captivity
    5.5 years
    AnAge

Behavior

Bunny rats are primarily social mammals, but can also be solitary depending on population densities. They are both diurnal and nocturnal, depending on the weather conditions. They construct burrows that go vertically into the turf and are from 4 to 7 cm in diameter. In their burrows they construct nests made of fine, dry grasses or wool in areas where they co-occur with sheep. (Nowak, 1999; Pardinas and Galliari, 2001)

Home Range

Home ranges have not been reported. (Pardinas and Galliari, 2001)

Communication and Perception

Little is known about specific forms of communication in bunny rats. Like other mammals, they are likely to use chemical communication to convey reproductive state.

Food Habits

Reithrodon auritus mainly feeds on grasses and other plants with tuberous rhizomes and roots. The stomach contents of bunny rats in southeastern Buenos Aires province showed that their diet consisted only of plant material, mostly grasses. Lolium multiflorum and Poa species made up 74% of stomach content dry weight. The variety of grasses in stomach contents was less than the variety of grasses available, suggesting that they may specialize on only a few types of grasses. Bunny rats in captivity eat their own body mass of green vegetation every night. (Pardinas and Galliari, 2001; Scaglia, et al., 1982)

  • Plant Foods
  • leaves
  • roots and tubers

Predation

Reithrodon auritus are main prey items throughout their range for great horned owls (Bubo virginianus), common barn owls (Tyto alba), other owl species, and buzzard-eagles. It is suggested that Patagonian opossums (Lestodelphys halli) are predators because they have been captured in the same trapline as Reithrodon auritus. Humans may eat bunny rats as well. Bunny rats don't seem to respond to noises, even as close as 2 meters away. Their cryptic coloration and escape to burrows may help protect them from predation somewhat. (Pardinas and Galliari, 2001)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Bunny rats are host to many ectoparasites. In Buenos Aires Province they are home to an endoparasite called Stilestrongylus aureus. They are also an important prey source for owls and small mammalian carnivores. (Pardinas and Galliari, 2001)

Bunny rats use burrows constructed by other species, including tuco-tucos (Ctenomys) and armadillos (Dasypodidae). They may inhabit these tunnels along with other rodent species, including long-haired grass mice (Abrothrix longipilis) and long-tailed pygmy rice rats (Oligoryzomys longicaudatus). (Pardinas and Galliari, 2001)

  • Ecosystem Impact
  • disperses seeds
Mutualist Species
Commensal/Parasitic Species

Economic Importance for Humans: Positive

Bunny rats are important members of their native ecosystems.

Economic Importance for Humans: Negative

Bunny rats have become pests in some areas because they consume such large quantities of grasses. At high population densities they can deteriorate pasture quality for cattle. (Pardinas and Galliari, 2001)

  • Negative Impacts
  • crop pest

Conservation Status

Reithrodon auritus populations are protected in some national parks and reserves but are not threatened or endangered. They are listed under lower risk and sublisted as a least concern on the IUCN redlist.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Nicholas Johnson (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

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.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

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.

diurnal
  1. active during the day, 2. lasting for one day.
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.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

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

polygynous

having more than one female as a mate at one time

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

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.

solitary

lives alone

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 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.

year-round breeding

breeding takes place throughout the year

young precocial

young are relatively well-developed when born

References

Nowak, R. 1999. Coney Rat. Pp. 1409 and 1410 in Walker's Mammals of the World, Vol. 2, 6 Edition. Baltimore, MD: John Hopkins University Press.

Pardinas, U., C. Galliari. 2001. Reithrodon auritus. Mammalian Species, American Society of Mammalogists, No. 664: 1-8.

Scaglia, O., C. Velazquez, M. Cauhepe. 1982. Plant composition of coney rat's (Reithrodon auritus) diet. Acta Theriologica, Vol. 27, no. 13-24: 350-353.

Wilson, D., D. Reeder. 1993. Coney Rat. Pp. 740 in Mammal Species of the World, Vol. 3, 2nd Edition. Washington, D.C.: Smithsonian Institution Presss.