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Caenolestes fuliginosussilky shrew opossum

By Leila Siciliano Martina

Geographic Range

Silky shrew opossums (Caenolestes fuliginosus) are found in central Ecuador, Columbia and northwestern Venezuela. Among other members of the genus Caenolestes, silky shrew opossums are found at higher elevations within the Andes Mountains. (Albuja V and Patterson, 1996; Boado, 2013; Lunde and Pacheco, 2003; Patterson, et al., 2008; Timm and Patterson, 2008)

Habitat

Silky shrew opossums are found at relatively high elevations from 1,400 to 4,300 m, however, the majority of trapped individuals have been found below 2,400 m. This species can be found in cloud forests, alpine tundra and upper montane forests. They are often found in the thick canopy in cool, moist environments, often with frequent rainfall. Silky shrew opossums may be excluded from areas with appropriate habitat due to their competition with wandering small-eared shrews, small mammals that fill a similar niche. (Albuja V and Patterson, 1996; Boado, 2013; Hunsaker II, 1977; Patterson, et al., 2008; Timm and Patterson, 2008; Tirira, 2010)

  • Range elevation
    1,400 to 4,300 m
    to ft

Physical Description

Silky shrew opossums are marsupials that are somewhat shrew-like in appearance and have elongated faces. Their glossy pelage is dark brown or dark gray and as their name suggests, their fur is very silky. The tips of their fur show a lighter color, with little counter-shading. There is little difference in coloration between their dorsal and ventral pelage. Compared to other members of their genus, silky shrew opossums have a relatively delicate build; these animals are smaller and have fragile skulls. Their head to body length ranges between 229 to 237 mm, including a dark brown tail that ranges between 107 to 113 mm. Their tails are semi-prehensile, and assist in climbing, although they cannot be used to solely support the animal’s weight. Their hind feet are relatively short, ranging from 20 to 21 mm in length. On average, these animals weigh between 34 to 39 grams. (Albuja V and Patterson, 1996; Boado, 2013; Hunsaker II, 1977; Kirsch and Waller, 1979; Timm and Patterson, 2008)

In general, members of family Caenolestidae can be distinguished from other marsupial groups by their unique dentition. Their lower middle incisors are large and have a forward slope; likewise, they have a reduced number of incisors. The dental formula for genus Caenolestes is: I 4/3, C 1/1, P 3/3, M 4/4, 46 teeth total. Shrew opossums have short robust limbs, each containing 5 digits; their middle 3 digits are shorter than the outside two. 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. (Boado, 2013; Lee and Cockburn, 1985; O'Connell, 2006; Osgood and Herrick, 1921; Tirira, 2007)

Common shrew opossums (Caenolestes obscurus), a close relative of silky 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)

  • Range mass
    34 to 39 g
    1.20 to 1.37 oz
  • Range length
    229 to 237 mm
    9.02 to 9.33 in

Reproduction

There is currently no information available regarding the mating systems of silky shrew opossums.

Female silky 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 trapped female had been discovered 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. Trapping practices have revealed at least 4 lactating silky shrew opossums in August. (Kirsch and Waller, 1979; O'Connell, 2006; Osgood and Herrick, 1921; Timm and Patterson, 2008; 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.

There is currently no information available regarding the parental investment of silky shrew opossums.

Lifespan/Longevity

There is currently no information available regarding the lifespan of silky 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. (Boado, 2013; Hunsaker II, 1977; O'Connell, 2006; Patterson and Solari, 2008; Timm and Patterson, 2008; Tirira, 2007; Tirira, 2010)

Home Range

There is currently no information available regarding the home range size of silky shrew opossums.

Communication and Perception

Members of family Caenolestidae have poor eyesight with very small eyes. Shrew opossums have tactile whiskers; their unusual lip flaps have the hypothesized function of clearing debris from these sensitive vibrissae, but they may merely function as a method of preventing the ingestion of unwanted debris. 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)

Food Habits

Members of genus Caenolestes are opportunistic feeders. Their stomach contents indicate that they are primarily insectivores, but they will also eat vertebrates and vegetation. Ingested invertebrates include beetles, flies, scarabs, crickets and grasshoppers, butterflies and butterfly larvae, centipedes, 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 Jr, 1984; Boado, 2013; Hunsaker II, 1977; Patterson and Solari, 2008; Timm and Patterson, 2008; Tirira, 2007; Tirira, 2010)

  • Animal Foods
  • mammals
  • insects
  • terrestrial non-insect arthropods
  • terrestrial worms
  • Plant Foods
  • leaves
  • fruit

Predation

There is currently little information regarding the predation of silky 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). (Lucherini, et al., 2009)

Ecosystem Roles

Silky 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. In addition, silky shrew opossums are often infested with fleas, chiggers, mites and lice. (Barkley and Whitaker Jr, 1984; Bochkov and O'Connor, 2009; Lee and Cockburn, 1985; Patterson and Solari, 2008; Timm and Patterson, 2008; Timm and Price, 1988; Tirira, 2007; VanZolini and Guimaraes, 1955)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

There are no known positive impacts of silky shrew opossums on human populations. This is partially because there has been very little interaction between our species. Silky shrew opossums are found in areas that are often inaccessible for humans. (Kirsch and Waller, 1979)

Economic Importance for Humans: Negative

There are no known negative impacts of silky shrew opossums on human populations.

Conservation Status

Silky shrew opossums are currently listed as a species of least concern according to the IUCN Red List of Threatened Species. This species is rarely seen by humans, but that is likely due to their human-inaccessible habitat and not a reflection of their population size. These animals likely have a large population and range; there are currently no immediate threats to this species. (Kirsch and Waller, 1979; Patterson, et al., 2008)

Other Comments

There are currently 3 recognized subspecies of silky shrew opossums, they include C.f. centralis, C.f. fuliginosus and C.f. obscurus. (Timm and Patterson, 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.

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.

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

omnivore

an animal that mainly eats all kinds of things, including plants and animals

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.

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

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

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.

References

Albuja V, 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 Jr. 1984. Confirmation of Caenolestes in Peru with information on diet. Journal of Mammalogy, 65:2: 328-330.

Boado, C. 2013. "Caenolestes fuliginosus" (On-line). Mammals of Ecuador. Accessed June 01, 2013 at http://zoologia.puce.edu.ec/vertebrados/mamiferos/FichaEspecie.aspx?ID=2060.

Bochkov, A., B. O'Connor. 2009. A new mite genus Caenolestomyobia Gen. Nov. (Acariformes: Myobiidae) from marsupials of the genus Caenolestes (Paucituberculata: Caenolestidae). Proceedings of the Zoological Institute, 313:4: 379-396.

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

Hunsaker II, D. 1977. The biology of marsupials. New York: Elsevier Science.

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. Cambridge: The Brown Reference Group.

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

Patterson, B., M. Gomez-Laverde, C. Delgado. 2008. "Caenolestes fuliginosus" (On-line). IUCN Red List of Threatened Species. Accessed June 01, 2013 at www.iucnredlist.org.

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

Timm, R., B. Patterson. 2008. Genus Caenolestes. Pp. 120-124 in A Gardner, ed. Mammals of South America: marsupials, xenarthrans, shrews, and bats, Vol. 1. Chicago: University of Chicago Press.

Timm, R., R. Price. 1988. A new Cummingsia (Mallophaga: Trimenoponidae) from a Peruvian mouse-opossum (Marsupialia). Journal of the Kansas Entomological Society, 61:1: 76-79.

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

Tirira, D. 2010. "Raton marsupial sedoso" (On-line). Mamiferos del Ecuador. Accessed June 01, 2013 at http://www.mamiferosdelecuador.com/diversidad/paucituberculata/caenolestidae/186-caenolestes-fuliginosus-tomes-1863.html.

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.

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