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Chestnut Tree Mouse

Pogonomys macrourus

French: Pogonomys a longue queue / German: Kastanienbraune Greifschwanzratte / Spanish: Raton arboricola de castano

Other common names: Chestnut Pogonomys, Prehensile-tailed Mouse, Soft-haired Tree Mouse, Tree Mouse

Taxonomy. Mus (Pogonomys) macrourus Milne-Edwards, 1877,

Amberbaki, Arfak Mountains, Vogelkop, Province of Papua, West Papua (= Irian Jaya), New Guinea.

Although more studies of the relationships within Hydromyini are needed, Pogonomys was found in S. J. Steppan and J. J. Schenk’s 2017 analysis to form a genetic clade with Hyomys (to which it is sister taxon), Chiruromys, Macruromys, Lorentzimys, and Anisomys, although with relatively low

support. P. macrourus as currently defined almost certainly represents a species complex. The Australian populations have been treated by most Australian authorities as a distinct species under the name mollipilosus, although this name is represented by a New Guinea specimen of uncertain taxonomic affinities (included in P. macrourus by some, and treated as distinct species by others). The name mollipilosus is included here under P. macrourus, although it may represent a distinct taxon. North Australian populations thus do not have an applicable name, although they are almost certainly a distinct species. There is also a possibly undescribed species in Foja Mountains. P. macrourus, as well as the whole genus,is in need of revision. Tentatively treated as monotypic.

Distribution. Throughout various mountainous areas of New Guinea, Yapen I, New Britain I, and extreme NE Australia (NE Queensland: Iron Range, and from Shiptons Flat to Koombooloomba).

Descriptive notes. New Guinea: head-body 92-150 mm, tail 126-187 mm, ear 11-15-5 mm, hindfoot 19-1-22-5 mm; weight 28-60 g. Australia: head—body 120-165 mm, tail 160-208 mm, ear 14-16 mm, hindfoot 22-27 mm; weight 42-83 g. The Chestnut Tree Mouse is a small to mid-sized species of Pogonomys with pelage soft and dense. Dorsal pelage is reddish brown in New Guinea and grayish brown in Australia, all populations with distinctive and thin dark eye-ring; ventral pelage is pure white and sharply demarcated from dorsal pelage. Feet are pinkish, sparsely furred dorsally, broad and short. Ears are small, dark around edges, and rounded; vibrissae relatively long. Tail is long (c.130% of head—body length), prehensile, thin, naked, and gray brown in color, commonly blotched with white in at least Australian populations. Skull is short and broad. Various species of cestode and nematode (Odilia, Pogonomystrongylus, etc.), as well as some fleas, have been recorded from New Guinea populations of this species. There are three pairs of mammae, one pectoral and two inguinal. Chromosomal complement for New Guinea populations is 2n = 46, FN = 42.

Habitat. Tropical moist primary and secondary forest in New Guinea and recorded in rainforests and monsoonal forests in Australia.

Food and Feeding. Chestnut Tree Mice are known to feed only on fruits and leaves, being strictly herbivorous. All information regarding feeding habits of this species is from Australia. Fruits of red-leaved figs ( Ficus congesta, Moraceae), Rhodomyrtus trineura (Myrtaceae), Amoora ferruginea ( Meliaceae), Pandanus monticola (Pandanaceae), bananas, and wild tobacco bush ( Solanum mauritianum, Solanaceae) are eaten, as well as leaves of yellow passionfruit vine ( Passiflora edulis flavicarpa, Passifloraceae). Some fruits are carried elsewhere for consumption (figs, tobacco bush, Rhodomyrtus), while others, because of their size, are eaten without being taken off the plant ( Pandanus and bananas). The outer surfaces of Pandanus fruits and bananas are bitten off and discarded to allow access to the inner fruit. Leaves of passionfruit vine are bitten offat the stalk and held in the forefeet when eaten, although the mouse may not completely finish them, dropping them on ground under the plant, where they will litter the floor (a useful clue for locating the animals). Chestnut Tree Mice generally forage alone, but up to three individuals have been seen eating together from a passionfruit.

Breeding. In New Guinea, breeding generally occurs in October—January and litter size is usually 2-3. In Telefomin area a female with two nearly independent young was captured in July, while a female with a single young was captured in Arfak Mountains in October. Reproductive activity of Australian populations is less known, but a female with two embryos was captured in September in Ordon Creek and two females (not breeding) were captured in July and February in Lake Barrine and Kuranda, respectively. Males with scrotal testes were captured during June-September, indicating that they were able to breed.

Activity patterns. The Chestnut Tree Mouse is strictly nocturnal. During day it rests in burrows on the ground, and in Australia has been reported to emerge at around 21:50 h. This species is arboreal and forages in trees, rarely coming to ground. Nests are built in burrows on ground, with nest chamber packed with leaves, usually with an escape hole hidden under leaves.

Movements, Home range and Social organization. Males are probably solitary, but 3-5 individuals (usually females) usually share a burrow, and up to 15 have been taken from a single burrow in New Guinea. In Australia, they move between trees and shrubs over pathways apparently used regularly, relying on their body weight to lower branches in order to bridge gaps. When disturbed, the tree mouse may hide among dense

leaves, as observed in a Pandanus in Australia, but it may also just continue moving throughout understory. Chestnut Tree Mice use the prehensile tail as support when moving through understory, grasping on sticks and twigs by curling the tail around them in a corkscrew pattern.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Chestnut Tree Mouse has a wide but scattered distribution, and is considered common but hard to see because of its arboreal nature. It is potentially found in various protected areas throughout New Guinea, and in Australia is found in the Wet Tropics World Heritage Area. It is apparently hunted for food in New Guinea. Although the Chestnut Tree Mouse is well known in Australia, there is a need for further research into the species in New Guinea, and into the taxonomy of the speciesitself, in order fully to understand its natural history and evolution, and any potential threats to it.

Bibliography. Breed & Aplin (1995), Dennis & Menzies (1979), Dwyer (1975), Flannery (1995a, 1995b), Hastriter & Easton (2013), Jackson & Groves (2015), Leary, Singadan, Menzies, Wright, Aplin & Helgen (2016), Musser & Carleton (2005), Smales (2014), Steppan & Schenk (2017).