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Rhyncholestes raphanurusChilean shrew opossum

By Andrew Moore

Geographic Range

Chilean shrew opossums have only been found in a small geographic range that covers southern Chile, Chiloe Island, and a small part of southern Argentina (approximately 40 degrees south latitude and 70 degrees west longitude). Captures of Rhyncholestes raphanurus occurred at elevations from sea level to 1135 m (Patterson and Gallardo, 1987). Only two specimens have been captured in Argentina. Once thought to be rare, it is possible that they are abundant in limited habitat types (Meserve et al, 1982). (Meserve, et al., 1982; Patterson and Gallardo, 1987)

Habitat

Chilean shrew opossums reside in temperate forest habitat. Favorable microclimates include wet areas of southern beech (Nothofagus species) forest with plenty of coarse woody debris and thick understory shrub cover. These marsupials are more frequently caught at elevations lower than 600 meters (Kelt and Martinez, 1989). (Kelt and Martinez, 1989)

  • Range elevation
    0 to 1135 m
    0.00 to 3723.75 ft

Physical Description

Chilean shrew opossums are small mammals. Their body size can range from 10 to 13 cm. Their ventral and dorsal portions are dark brown or gray. The tail is solid in color, with short, sparse hairs, and shorter than the head and body.Their shape is shrew-like and the ears are small and rounded (Redford et al, 1992). Determination of gender is through dental formula- males have a conical, single rooted upper canine and females have a double-rooted canine resembling a premolar (Patterson and Gallardo, 1987). (Patterson and Gallardo, 1987; Redford and Eisenberg, 1992)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    10 to 13 cm
    3.94 to 5.12 in

Reproduction

Little is known about caenolestid mating systems. The seemingly solitary behavior of Chilean shrew opossums (Kelt and Martinez, 1989), as well as random distribution of resources in their environment, suggests a polygynandrous (promiscuous) mating system. Other hypotheses include that they live in family groups which would suggest monogamous mating systems. Neither hypotheses have been tested. (Kelt and Martinez, 1989)

Few studies have been done on the reproductive cycle of Chilean shrew opossums. Females do not have a pouch and possess five to seven teats. Patterns of teat development suggest litters of 5 to 7 or greater (Patterson and Gallardo, 1987). There is evidence that females are capable of reproducing any time of the year, as lactating females have been captured in February, March, May, October, November and December (Nowak, 1999). Males are thought to be reproductively active all year. They possess a cleft penis and paired sperm (Patterson and Gallardo, 1987). (Nowak, 1999; Patterson and Gallardo, 1987)

  • Breeding interval
    Breeding intervals are unknown in Chilean shrew opossums.
  • Breeding season
    Chilean shrew opossums may breed throughout the year.
  • Range number of offspring
    5 to 7

Little is known about parental care in R. raphanurus. A mother with young has never been captured, suggesting they may use a nest to raise young. The trapping of an adult male, adult female and two juveniles in one trap in a short time period led to the hypothesis that R. raphanurus live in family groups, indicating that both male and female participate in care of young. This hypothesis has not yet been tested (Patterson and Gallardo, 1987). (Patterson and Gallardo, 1987)

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

Lifespan / Longevity

No data has been gathered on the life span of Chilean shrew opossums. Few trapped individuals have been recaptured, making it difficult to judge life span (Meserve et al, 1982). Because of their small body size, it is likely that they do not live more than a few years. (Meserve, et al., 1982)

Behavior

Chilean shrew opossums are usually caught at night, indicating they are nocturnal. They are often caught near burrows and under logs and appear to be semi-fossorial, foraging under leaf litter for insects. Lack of recapture indicates trap shyness, high post-capture mortality, or large home range (Kelt and Martinez, 1989). (Kelt and Martinez, 1989)

Home Range

Due to lack of recapture data or radio tracking, home range is not known for Chilean shrew opossums.

Communication and Perception

Little is known about the communication of Chilean shrew opossums or how they perceive their environment. They likely have poor eyesight due to nocturnal activity and small eyes. Vibrissae are used to sense insects and objects in the environment. Examination of their brains shows large olfactory bulbs, indicating an acute sense of smell (Patterson and Gallardo, 1987). (Patterson and Gallardo, 1987)

Food Habits

Chilean shrew opossums are semi-fossorial, foraging in the litter layer for soil invertebrates (54% of diet) and earthworms (7%). Another principle component of their diet is plant material and fungi (39%), and they are commonly baited into traps with rolled oats (Meserve et al, 1988). (Meserve, et al., 1988)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • Plant Foods
  • seeds, grains, and nuts
  • Other Foods
  • fungus

Predation

Little data has been gathered on predation on Chilean shrew opossums. Like most small mammals, they are likely a food base for nocturnal carnivores. Possible vertebrate predators include Buteo polyosoma, Elanus leucurus, Falco sparverius, Geranoaetus melanoleucus, Parabuteo unicinctus; Athene cunicularia, Bubo virginianus, Tyto alba, Dusicyon culpaeus (Lycalopex culpaeus), Philodryas chamissonis, and Tachymenis peruviana (Jaksie et al, 1980). (Jaksic, et al., 1980)

Chilean shrew opossums are small, cryptic, nocturnal animals and likely avoid most predation by being difficult to find. (Nowak, 1999)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Other than their consumption of insects, earthworms and plant material and fungi, little is known about the ecosystem roles of R. raphanurus.

Economic Importance for Humans

Economic Importance for Humans: Positive

Due to few studies, economic importance of Chilean shrew opossums is not known.

Economic Importance for Humans: Negative

Due to few studies, economic importance of Chilean shrew opossums is not known.

Conservation Status

Chilean shrew opossums were listed in 1994 by the IUCN (International Union for Conservation of Nature and Natural Resources) as vulnerable due to habitat loss and degradation.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Andrew Moore (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

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.

carnivore

an animal that mainly eats meat

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.

forest

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

insectivore

An animal that eats mainly insects or spiders.

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.

mycophage

an animal that mainly eats fungus

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sedentary

remains in the same area

sexual

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

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.

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

References

Chebez, C. 2000. "The marsupials of Argentina" (On-line). Accessed November 03, 2006 at http://www.cricyt.edu.ar/INSTITUTOS/iadiza/ojeda/MARSUPIALES.htm.

Jaksic, F., H. Greene, J. Yanez. 1980. The guild structure of a community of predatory vertebrates in central Chile. Oecologia, 49: 21-28.

Kelt, D., D. Martinez. 1989. Notes on distribution and ecology of two marsupials endemic to the Valvidian forests of southern South America. Journal of Mammalogy, 70: 220-224.

Meserve, P., B. Lang, B. Patterson. 1988. Trophic relations of small mammals in a Chilean Temperate Forest. Journal of Mammalogy, 69: 721-730.

Meserve, P., R. Murua, O. Lopetegui, J. Rau. 1982. Observations on the Small Mammal Fauna of a Primary Temperate Rain Forest in Southern Chile. Journal of Mammalogy, 63: 315-317.

Nowak, R. 1999. Mammals of the World. Baltimore, Maryland: John Hokpkins University Press.

Patterson, B., M. Gallardo. 1987. Mammalian Species- Rhyncholestes raphanurus. American Society of Mammalogists, 286: 1-5.

Patterson, B., P. Meserve, B. Lang. 1990. Quantitative habitat associations of small mammals along an elevational transect in temperate rainforests of Chile. Journal of Mammalogy, 71: 620-623.

Redford, K., J. Eisenberg. 1992. Mammals of the Neotropics- The Southern Cone. Chicago, Illinois: University of Chicago Press.

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