Rhyncholestes raphanurus, Osgood, 1924

Russell A. Mittermeier & Don E. Wilson, 2015, Caenolestidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 188-197 : 196-197

7.

Long-nosed Shrew-opossum

Rhyncholestes raphanurus

French: Cénoleste du Chili / German: Langnasen-Opossummaus / Spanish: Ratén marsupial trompudo

Other common names: Chilean Caenolestid, Chilean Shrew-opossum, Fat-tailed Caenolestid, Long-nosed Caenolestid

Taxonomy. Rhyncholestes raphanurus Osgood, 1924 , “ mouth of Rio Inio , south end of Chiloé Island ,” Los Lagos Region, Chile.

The subspecies continentalis was originally described as a distinct species on the basis of height of the secondary cusp on canine teeth of females. Two subspecies recognized.

Subspecies and Distribution.

R. r. raphanurus Osgood, 1924 — Chiloé 1,

S Chile.

R. r. continentalis Bublitz, 1987 — SC Chile mainland (Los Lagos) and adjacent Argentina (Nahuel Huapi National Park).

Descriptive notes. Head-body 9.7-12.8 cm, tail 6:5.8-8 cm, hindfoot 1.9-2.4 cm; weight 23-30 g, but up to 36-40 g. Male LLong-nosed Shrew-opossums tend to be somewhat larger than females. Long-nosed Shrew-opossums are characterized by having a very long rostrum, open palate, double infraorbital foramen, subequally bifid lateral upperincisors, and sexually dimorphic upper canines, which are single rooted and caniniform in males and double-rooted and premolariform in females. Unlike other shrew-opossums, but like some other marsupials living in highly seasonal environments such as the fat-tailed mouse opossums (7hylamys spp.), the Patagonian Opossum (Lestodelphys hall), and the Monito del Monte (Dromiciops gliroides), the tail of the Long-nosed Shrew-opossum swells seasonally with fat stores, from 4-5 mm in proximal diameter during summer to 9-11 mm in early winter. The specific epithet raphanurus (“radish tail”) refers to this seasonal accumulation of fat in the tail. Females were thought to have four inguinal and one abdominal mammae, but three abdominal mammae are present in some, the odd one invariably on the ventral midline. Longnosed Shrew-opossums are host to a large commensal rove beetle, Chilamblyopinus piceus, and the fleas Barreropsylla excelsa, Cleopsylla vidua, Plocopsylla athena, and Plocopsylla diana.

Habitat. Appears restricted to temperate rainforest habitats, with Nothofagus (Nothofagaceae) as the overstory dominant and a dense understory of Chusquea (Poaceae) , Podocarpus and Saxegothaea (both Podocarpaceae ). Predictive models of the distribution of the Long-nosed Shrew-opossum have strong contributions from precipitation and precipitation-related variables. It is captured mainly on moist ground, at the bases of trees, alongside moss-covered logs, and in dense cover. It has also been recorded in or near disturbed areas and has been captured in isolated forest remnants in regions dominated by agriculture and grazing. The Long-nosed Shrew-opossum occurs from sea level on Chiloé Island to an elevation of 1135 m along the slopes of the Osorno Volcano (La Picada, Los Lagos Region, Chile).

Food and Feeding. At La Picada, the diet of Long-nosed Shrew-opossums consisted of invertebrates (55%) and vegetation and fungi (40%); annelid worms accounted for 8% of all food ingested. One individual caged with a newly captured Abrothrix sp. (a mouse also native to Valdivian forests) made no attempt to prey on it, as would species of Caenolestes in similar circumstances.

Breeding. Female L.ong-nosed Shrew-opossums are reproductively active during austral summer; lactating or pregnant females have been recorded in December—March and in May, October, and November. No young have ever been found attached to nipples of lactating females, raising the prospect that they use a nest to rear offspring. Male Long-nosed Shrew-opossums appear to be sexually active throughout the year and have been noted with well-developed testes in February, March, and May.

Activity patterns. At La Picada, all but one capture of Long-nosed Shrew-opossums took place at night, suggesting that they are strongly nocturnal. Caudalfat storage has been associated with seasonal activity patterns and extended torpor in other marsupials, but Long-nosed Shrew-opossums have been captured during winter on snowpack. Year-round activity and an evident inability to arouse from hypothermia suggest that they do not rely on hibernation or torpor to any great extent. Long-nosed Shrewopossums do not thrive in captivity and attempts to maintain them in cages on varied diets have failed after only a day or two.

Movements, Home range and Social organization. In four years oflive trapping at La Picada, only two of 36 released LLong-nosed Shrew-opossums were recaptured. Successive captures of adults and juveniles in the same trap did suggest that they might live in family groups. Casual observations of newly captured individuals suggest the Longnosed Shrew-opossum may be slower,less agile, and morestrictly terrestrial than other shrew-opossums.

Status and Conservation. Classified as Near Threatened on The IUCN Red List. The Long-nosed Shrew-opossum has a localized geographical distribution and is strongly associated with intact Nothofagus forests, a habitat type that is being heavily exploited. Although the Long-nosed Shrew-opossum has been recorded from remnant forests in agricultural landscapes, it does not inhabit naturally disturbed areas (e.g. bamboochoked landslides), even those alongside primary forests where it is relative abundant. An ongoing population decline is inferred from habitat loss due to logging activities and the paucity of new occurrence records (the last new distribution record, from 1997, was a shrew-opossum taken by a raptor). The Long-nosed Shrew-opossum can be considered a diagnostic element of the Valdivian biogeographic province. Like the cricetid rodents Pearson’s Long-clawed Mouse (Pearsonomys annectens) and Sanborn’s Soft-haired Mouse (Abrothrix sanborni), itis found only in the center of the larger Valdivian ecoregion. Further information is needed on distribution, area of occupancy, and effects of threats on populations of the Long-nosed Shrew-opossum, because it may be more threatened than currently suspected. The Long-nosed Shrew-opossum may qualify for Threatened status under IUCN’s population decline criteria (criterion A).

Bibliography. Ashe & Timm (1988), Beaucournu & Gallardo (1991), Beaucournu & Kelt (1990), Birney, Sikes et al. (1996), Bublitz (1987), Flores et al. (2007), Gallardo & Patterson (1987), Iriarte (2008), Kelt (2000), Kelt & Martinez (1989), Mann (1978), Martin (2007, 2011), Meserve, Kelt & Martinez (1991), Meserve, Lang & Patterson (1988), Meserve, Murua et al. (1982), Monjeau, Bonino & Saba (1994), Monjeau, Sikes et al. (1997), Osgood (1924), Patterson (2007b), Patterson & Gallardo (1987), Patterson et al. (1989, 1990), Pine et al. (1979), Tamayo et al. (1987).

Figures

1. Gray-bellied Shrew-opossum (Caenolestes caniventer), 2. Condor Shrew-opossum (Caenolestes condorensis), 3. Blackish Shrew-opossum (Caenolestes convelatus), 4. Dusky Shrew-opossum (Caenolestes fuliginosus), 5. Sangay Shrew-opossum (Caenolestes sangay), 6. Incan Shrew-opossum (Lestoros inca), 7. Long-nosed Shrew-opossum (Rhyncholestes raphanurus)

Subspecies and Distribution. R. r. raphanurus Osgood, 1924 — Chiloé 1, S Chile. R. r. continentalis Bublitz, 1987 — SC Chile mainland (Los Lagos) and adjacent Argentina (Nahuel Huapi National Park).