674.

Chilean Climbing Mouse

Irenomys tarsalis

French: Irenomys du Chili / German: Chile-Ratte / Spanish: Ratén trepador de Chile

Other common names: Chilean Tree Rat, Large-footed Irenomys

Taxonomy. Mus tarsalis Philippi, 1900, near La Union, Fundo San Juan, Los Rios, Chile. Validity of an island race, longicaudatus restricted to Isla Melinka in southern Chile needs to be compared taxonomically to I. tarsalis . Monotypic.

Distribution. C & S Chile and adjacent Argentina.

Descriptive notes. Head-body 108-130 mm, tail 162-196 mm, ear 20-25 mm, hindfoot 28-32 mm; weight 30-67 g. Males and females are of the same weight. The Chilean Climbing Mouse is medium-sized, with tail ¢.150% longer than head-body length. Pelage is thick and soft. Ears are of medium length and densely haired. Eyes are large. Forefeet and hindfeet are large and broad. Heel is only sparsely furred. Dorsum is grayish cinnamon rufous, streaked with fine dusky lines. Underparts are plumbeous, heavily washed with pinkish cinnamon buff. Ears are brownish black, occasionally with indistinct subauricular white spot. Forefeet and hindfeet are whitish; toes are white. Tail 1s unicolored blackish brown, conspicuously clothed with short hairs, and ends in a short (c.5 mm) pencil of hairs. Chromosomal complement is 2n = 64 and FN = 98.

Habitat. Dense Nothofagus (Nothofagaceae) forest with thick stands of Chusquea (Poaceae) bamboo and more rarely ecotone and xeric environments of transition from temperate Nothofagus rainforest to steppe. Also collected in shrubby habitats in and in the more arid fringes of cypress trees ( Austrocedrus chilensis, Cupressaceae) and in exotic Pinus contorta ( Pinaceae) plantations.

Food and Feeding. The Chilean Climbing Mouse east seeds,fruit, and plant parts but also minor proportions of fungi and insects. A captive individual ate rolled oats, apple, and tender bamboo shoots but refused carrot, bamboo blossoms, bread, and grubs.

Breeding. The Chilean Climbing Mouse breeds in spring, but reproduction can extend to late summer or early autumn. Litters have 3-6 young. A nest occupied by a female with three young was located inside the hollow of a living lenga beech ( Nothofagus pumilio); its nest was placed 2 m aboveground and inside an oval hollow, with two openings on the upper part and opposite of the main cavity entrance; and it was built with a few feathers and lichens, dry and fine grass, pieces of small sticks, and scraped material from inside the trunk.

Activity patterns. The Chilean Climbing Mouse is nocturnal. It is frequently captured in traps placed along logs, at bases of trees, or in hollows formed by surface roots and boulders covered by lichens and mosses. It was the second most common mammal observed in arboreal stratum with camera traps.

Movements, Home range and Social organization. Chilean Climbing Mice climb well, sometimes jumping a few centimeters from one branch to another, or they can hold on with hindfeet and reach across gaps with extended front feet. Tendency to nest in trees supports the notion of an ancient association between Chilean Climbing Mice and Nothofagus forest. This connection could be reflected in its ability to climb at high speed, mainly favored by turgent palmar and plantar pads and long strong tail, with prehensile capacity. Densities in a coihue ( Nothofagus dombeyi) forest varied from 1-4 ind/ha in November to 5-1 ind/ha in May.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Chilean Climbing Mouse has been considered rare or uncommon, a view probably resulting from low capture success when traps are placed on the ground.

Bibliography. Amico & Aizen (2000), Formoso & Sanchez (2014), Garcia et al. (2011), Honorato et al. (2016), Kelt (1993, 1994, 1996), Kelt et al. (2008), Mann (1978), Martin (2010), Meserve et al. (1988), Monjeau et al. (1997), Ojeda et al. (2004), Osgood (1943a), Pardinas, Patterson et al. (2016a), Patterson etal. (1989, 1990), Pearson (1983, 1995), Pearson & Pearson (1982), Philippi (1900), Saavedra & Simonetti (2000), Silva (2005), Teta & Pardinas (2015a), Thomas (1919a).