Rhyncholestes raphanurus
Chilean shrew opossum

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)

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)

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)

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)

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)

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)

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)

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

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)

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)

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)

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

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

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

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.