Caenolestes caniventergray-bellied shrew opossum

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Geographic Range

Gray-bellied shrew opossums (Caenolestes caniventer) are found in central Ecuador and northwestern Peru, primarily on the Pacific slopes of the Andes Mountains. Individuals have been trapped in Ecuador in the following locations: El Oro Province, near Mount Cayambe and Molleturo. (Albuja and Patterson, 1996; Barnett, 1991; Patterson and Solari, 2008)

Habitat

Gray-bellied shrew opossums reside in subtropical and montane forests of the Andes Slopes at elevations above 1,500 meters. These animals prefer cool wet areas and create channels under root systems along streams in wet grasslands. (Albuja and Patterson, 1996; Barnett, 1991; Patterson and Solari, 2008; Tate, 1931; Timm and Patterson, 2008)

  • Range elevation
    1,500 (low) m
    (low) ft

Physical Description

Gray-bellied shrew opossums are marsupials, they are somewhat shrew-like in appearance, with elongated faces. They can be distinguished from their close relative, silky shrew opossums (Caenolestes fuliginosus), by the coarse thickness of their brownish-black fur. Their fur is relatively long, about 10 mm in length and is occasionally tipped in white. Their under-fur has a grayish-white hue and they commonly have dark spots on their chest. Gray-bellied shrew opossums have an average total body length of 256 mm, including a tail length of 127 mm and weigh about 40 grams. (Lunde and Pacheco, 2003; Osgood and Herrick, 1921; Tirira, 2007)

In general, members of family Caenolestidae can be distinguished from other marsupial groups by their unique dentition. They have a reduced number of incisors and their lower middle incisors are large and have a forward slope. The dental formula for genus Caenolestes is: I 4/3, C 1/1, P 3/3, M 4/4, 46 teeth total. Their tail is long, about as long as their body, and appears rat-like and hairless, although it is covered in white fur. While their tail is not prehensile, it is used for support while they climb. Shrew opossums have short robust limbs, each containing 5 digits; their middle 3 digits are shorter than the outside 2. Their humeri are extremely heavy; in comparison, their femurs are relatively slender. Members of family Caenolestidae have unusual lip flaps, they may function as a method of preventing debris from interfering with their whiskers or they may help prevent ingestion of unwanted debris. Similar to other marsupials, Caenolestid females have 2 uteri and 2 vaginas. Members of genus Caenolestes lack a pouch but do have 4 mammae, 2 on either side of their abdomen. These animals show sexual dimorphism, with adult males larger than adult females. (Lee and Cockburn, 1985; O'Connell, 2006; Osgood and Herrick, 1921; Tirira, 2007)

Common shrew opossums (Caenolestes obscurus), a close relative of gray-bellied shrew opossums, show evidence of a low metabolic rate, based on their body temperature (35.4° C), their body weight (about 40 g), their cool habitat and their thick fur coat. This species shows no evidence of entering torpor. (McNab, 1978)

  • Sexual Dimorphism
  • male larger
  • Average mass
    40 g
    1.41 oz
  • Average length
    256 (including the tail) mm
    in

Reproduction

There is currently little information available regarding the mating system of gray-bellied shrew opossums.

Female gray-bellied shrew opossums lack a marsupium; however, immature individuals may have an undeveloped fold of skin that they lose before reaching maturity. Females have 4 mammae available for their young to nurse. Evidence suggests that Caenolestid females have the same number of ova as mammae, unlike family Didelphidae. In support of that notion, a female was found pregnant with 3 embryos, 2 in the right uterus and 1 in the left. These animals likely have one annual breeding season from February to August. Likewise, there was a confirmed report of a pregnant female trapped in the month of September. (O'Connell, 2006; Osgood and Herrick, 1921; Tirira, 2007; Tyndale-Biscoe and Renfree, 1987)

  • Breeding interval
    Members of family Caenolestidae likely breed once per year.
  • Breeding season
    The breeding season of family Caenolestidae is likely between February and August.

No information is currently available regarding this species.

Lifespan/Longevity

There is currently no information on the longevity of gray-bellied shrew opossums.

Behavior

Members of genus Caenolestes are solitary; they are primarily active during the early evening and at night. They are terrestrial, but they are also adept climbers. During the day, these animals stay in tunnels under tree roots. When they are active, they travel through paths in dense vegetation. (O'Connell, 2006; Patterson and Solari, 2008; Timm and Patterson, 2008; Tirira, 2007)

Home Range

Little is known about the home range size of this species.

Communication and Perception

Members of family Caenolestidae have very small eyes and poor eyesight. Their unusual lip flaps have the hypothesized function of clearing debris from their sensitive vibrissae, but they may merely function as a method of preventing the ingestion of unwanted debris. Their somewhat primitive brains have enlarged olfactory bulbs, which could indicate an enhanced sense of smell. When they are startled they attempt to hide and they hiss when cornered. Caenolestids are not noted for frequent production of sound, however, captive individuals may make several sounds including whistles, bird-like screams, rat-like squeaks and drawing air through their incisors. (Hume, 1982; Kirsch and Waller, 1979; O'Connell, 2006; Vaughan, et al., 2011)

Food Habits

Members of genus Caenolestes are opportunistic feeders. Their stomach contents indicate that they are primarily insectivorous. Ingested invertebrates include beetles, crickets, butterfly larvae, centipedes, grasshoppers, spiders, and earthworms. A smaller proportion of their diet is composed of vegetation, fruit and small vertebrates including juvenile mice. They forage for food in moss and leaf litter. When they find a food item, they manipulate and consume it with their forepaws, from a semi-seated position. As Caenolestids shear their food with their incisors, they produce a clicking sound. (Barkley and Whitaker, 1984; Patterson and Solari, 2008; Timm and Patterson, 2008; Tirira, 2007)

  • Animal Foods
  • mammals
  • carrion
  • terrestrial worms
  • Plant Foods
  • leaves
  • fruit

Predation

There is currently little information regarding the predation of gray-bellied shrew opossums. However, there are several carnivores known to inhabit a similar range and prey upon small mammals, such predators include Andean Mountain cats (Leopardus jacobita), pampas cats (Leopardus colocolo), culpeo foxes (Lycalopex culpaeus) and cougars (puma concolor), among others. (Lucherini, et al., 2009)

Ecosystem Roles

Gray-bellied shrew opossums have an insectivorous diet. Likewise, Caenolestids are often plagued by lice of the genus Cummingsia. Interestingly, Australian marsupials are also affected by similar lice, related to the family level. Caenolestids may also become infested with South American hard ticks (Ixodes jonesae). (Barkley and Whitaker, 1984; Lee and Cockburn, 1985; Patterson and Solari, 2008; Tirira, 2007; VanZolini and Guimaraes, 1955)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Due to the human-inaccessible habitat of gray-bellied shrew opossums, there has been very little study of these animals. Likewise, there has been very little interaction between human and shrew opossum populations. They may, however, serve as a control of insect populations. (Kirsch and Waller, 1979; Patterson and Solari, 2008)

Economic Importance for Humans: Negative

There are no known negative impacts of gray-bellied shrew opossums on human populations.

Conservation Status

Gray-bellied shrew opossums are currently listed as a near threatened species on the IUCN Red List, with a declining population. This species is particularly vulnerable to habitat loss due to timber sales and the conversion of land to agriculture. This species may not be rare within its habitat; however, it is difficult to ascertain because its range is largely inaccessible to humans. (Kirsch and Waller, 1979; Patterson and Solari, 2008)

Contributors

Leila Siciliano Martina (author), Animal Diversity Web Staff.

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

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

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

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.

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

seasonal breeding

breeding is confined to a particular season

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.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Albuja, L., B. Patterson. 1996. A new species of northern shrew-opossum (Paucituberculata: Caenolestidae) from the Cordillera del Condor, Ecuador. Journal of Mammalogy, 77:1: 41-53.

Barkley, L., J. Whitaker. 1984. Confirmation of Caenolestes in Peru with information on diet. Journal of Mammalogy, 65:2: 328-330.

Barnett, A. 1991. Records of the grey-bellied shrew opossum, Caenolestes caniventer and Tate's shrew opossum, Caenolestes tatei (Caenolestidae, Marsupialia), from Ecuadorian montane forests. Mammalia, 55:3: 443-445.

Hume, I. 1982. Digestive physiology and nutrition of marsupials. Cambridge: Cambridge University Press.

Kirsch, J., P. Waller. 1979. Notes on the trapping and behavior of the Caenolestidae (Marsupialia). Journal of Mammalogy, 60:2: 390-395.

Lee, A., A. Cockburn. 1985. Evolutionary ecology of marsupials. Cambridge: Cambridge University Press.

Lucherini, M., J. Reppucci, R. Walker, M. Villalba, A. Wurstten, G. Gallardo, A. Iriarte, R. Villalobos, P. Perovic. 2009. Activity pattern segregation of carnivores in the high Andes. Journal of Mammalogy, 90:6: 1404-1409.

Lunde, D., V. Pacheco. 2003. Shrew Opossums (Paucituberculata:Caenolestes) from the Huancamba region of east Andean Peru. Mammal Study, 28: 145-148.

McNab, B. 1978. The comparative energetics of Neotropical marsupials. Journal of Comparative Physiology, 125: 115-128.

O'Connell, M. 2006. Shrew opossums of the high Andes. Pp. 812 in D MacDonald, S Norris, eds. The Encyclopedia of Mammals, Vol. 1, 1 Edition. London: The Brown Reference Group.

Osgood, W., C. Herrick. 1921. A monographic study of the American marsupial, Caenolestes. Chicago: The University of Chicago.

Patterson, B., S. Solari. 2008. "Caenolestes caniventer" (On-line). The IUCN Red List of Threatened Species. Accessed May 17, 2013 at http://www.iucnredlist.org/.

Tate, G. 1931. Random observations on habits of South American mammals. Journal of Mammalogy, 12:3: 248-256.

Timm, R., B. Patterson. 2008. Genus Caenolestes. Pp. 120-124 in A Gardner, ed. Mammals of South America: Volume 1- Marsupials, Xenarthrans, Shrews, and Bats, Vol. 1. Chicago: University of Chicago Press.

Tirira, D. 2007. Mamiferos del Ecuador: Guia de campo. Ecuado: Ediciones Murcielago Blanco.

Tyndale-Biscoe, H., M. Renfree. 1987. Reproductive physiology of marsupials. Cambridge: Cambridge University Press.

VanZolini, P., L. Guimaraes. 1955. South American land mammals and their lice. Evolution, 9:3: 345-347.

Vaughan, T., J. Ryan, N. Czaplewski. 2011. Mammalogy. Sudbury, Massachusetts: Jones and Bartlett Publishing.