Caenolestes caniventer

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.

• Biogeographic Regions
• neotropical neotropical
  • native native

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.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• mountains mountains

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.

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.

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.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

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.

• Key Behaviors
• terricolous
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• solitary solitary

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.

• Communication Channels
• tactile tactile
• acoustic acoustic

• Perception Channels
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• mammals
• carrion 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.

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 ).

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.

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.

Additional Links

Encyclopedia of Life

Contributors

Leila Siciliano Martina (author), Texas State University.

References

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