331.

Brush-tailed Rabbit Rat

Conilurus penicillatus

French: Conilure a pinceau / German: Blrstenschwanz-Kaninchenratte / Spanish: Rata conejo de cola de cepillo

Other common names: Brush-tailed Conilurus, Brush-tailed Tree Rat, Rabbit-eared Tree Rat

Taxonomy. Mus penicillatus Gould, 1842,

“Port Essington” (Port Essington District, Cobourg Peninsula, Northern Territory, Australia).

Long-established genus name Conilurus W. Ogilby, 1838 is an emendation of Conylurus W. Ogilby, 1837. J. A. Mahoney and B. J. Richardson in 1988 recommended that the earlier name be treated as an unused senior synonym. Molecular evidence places Australo-Papuan genus Conilurus

close to Mesembriomys and Leporillus, both of which are exclusively Australian in distribution; closest molecular affinity is to Mesembriomys, and this is supported by morphological similarities that include brush-like tail and presence of a seventh cusp (t7) on each first upper molar. There are two synonyms of typical penicillatus: Hapalotis melanura, a junior objective synonym proposed for Gould’s specimen from Port Essington; and Hapalotis hemileucura, based on a series of poorly localized specimens from somewhere in “interior of Australia from the north-west coast of Australia to Moreton Bay [south-east Queensland].” Type series of hemileucura has been surmised to come from Victoria River region of Northern Territory, but cranial features and external dimensions fall outside range of geographic variation observed in the nominate penicillatus . Further genetic investigation is recommended. Two regional populations, each described as full species,are listed here as subspecies, following recent usage; their degree of distinctness should be further tested by genetic methods. Genus Conilurus contains two other, extinct species: C. albipes of SE Australia survived until early 1860s; and C. capricornensis of north-east Queensland, not recorded historically but represented by skeletal remains of probable late Holocene from caves. Three subspecies recognized.

Subspecies and Distribution.

C.p.penicillatusGould,1842—coastalareasoftheKimberleyregionofWesternAustralia,NorthernTerritory,andNWQueensland,Australia;alsorecordedfromvariousIsincludingInglis(EnglishCompanyIs),GrooteEylandt,SirEdwardPellewGroupIs,andBentinck.

C.p.melibiusThomas,1921—MelvilleandBathurstIs,TiwiIs,NorthernTerritory,Australia.

C. p. rand: Tate & Archbold, 1938 — known only from the vicinity of Morehead, Trans Fly region, S New Guinea; current status uncertain.

Descriptive notes. Head-body 152-195 mm, tail 170-215 mm, ear 25-30 mm, hindfoot 36-48 mm; weight 110-170 g. Males average slightly heavier than females and have slightly longer hindfeet. The Brush-tailed Rabbit Rat is a moderately large arboreal murine with unusually large eyes and distinctive, brushy tail; fur on upperparts is moderately long and shaggy, mildly rough to touch. Overall fur color on back and head is grayish brown, strongly brindled owing to presence of numerous black-tipped guard hairs that are longest and most numerous along mid-back and on rump; fur on nape and shoulders often with strong orange tints. Flanks are slightly paler and grade into paler hues of underparts, fur on which varies from white to cream to pale tan, usually with short medium-gray bases; many individuals have dark gray chest patch, often T-shaped, and some also have patches of pure white fur along midline. Palefur of underparts extends onto inner surfaces of limbs and throat and to throat and lower cheek. Head is broad and deep, with relatively short snout; eyes large, with narrow ring of short black hairs; top of snout dark but vibrissal pads pale gray; vibrissae dark gray to black, relatively thin but long, extending back to shoulders; ears moderately large but rounded, with gray skin and covering of fine silvery hairs. Fur on lower forelimb and forefeet white,fur on hindfeet white only from ankle; forefeetwith four strong curved claws, all finely pointed, inner digit with nail; hindfeet elongate and with unpigmented skin and six, moderately large plantar pads including an elongate post-hallucal pad, and strong but curved claws on all digits. Tail is long (100-126% of head-body length), tail scales flat and weakly overlapping, 11-12 rows per cm at mid-tail, each scale with three hairs; basal 10% oftail is gray and thinly furred, remainder with more heavily pigmented scales and increasingly elongate hairs, creating distinct brush that projects well past end oftail vertebrae. Hairs on tail are black to tip among individuals from Cobourg Peninsula and areas farther east, but variably all black or white-tipped in other populations, most frequently so in Kimberley region of Western Australia (42% white-tipped) and on Bathurst and Melville Islands (subspecies melibius, 40%), and less so in Arnhem Land region ofnorth-west Northern Territory (27%); tail tip is white in at least one individual from Papua New Guinea. Mammae two on each side, one postaxillary and two inguinal. Adult males with testes of above-average mass compared with other Murinae. Cranium is robust, with proportionally large molars, moderately large auditory bullae, and strongly arched dorsal profile. Karyotype with 2n = 28, including 21 pairs of telocentric autosomes in a graded series, and two small metacentric pairs. Identical autosomal complements are recorded in species of Mesembriomys and Leggadina, and in some Melomys species, and this is interpreted as an ancestral arrangement for Australian Hydromyini . X chromosome is a large acrocentric; Y chromosome not reported. Spermatozoa with moderately long tail (116 pm), and relatively short (7 pm) sperm head that is broad basally, with narrow apical hook and two accessory ventral hooks. Glans penis, as described by W. Z. Lidicker and P. V. Brylski in 1987, has robust baculum with broad, notched base, a large dorsal papilla and an outer crater rim that is completely papillate; it closely resembles condition in the Black-footed Tree Rat ( Mesembriomys gouldii). New Guinea subspecies randi is larger overall and has longer hindfeet than all Australian samples except poorly localized type series of hemileucura (which may come from an otherwise unsampled region); these samples also possess somewhat larger molars than other populations. Tiwi Island subspecies melibius has proportionally shorter hindfeet and ears, and fur on underparts is creamy brown and lacks gray bases to hairs.

Habitat. Preferred habitat of the Brush-tailed Rabbit Rat across its Australian range is eucalypt tall open forest, but locally it is also recorded from stunted eucalypt woodlands, from groves of she-oak ( Casuarina equisetifolia, Casuarinaceae) growing along coastal strandlines, and from margins of monsoon forest;it is commonly associated with pandan palms ( Pandanus, Pandanaceae). On Tiwi Islands, subspecies melibius shows strong preference for lowland terrain with taller open eucalypt forest with mixed shrub and grass cover, and is less abundant in drier upland areas; it isabsent from all parts where native forests have been replaced by plantations of exotic black wattle ( Acacia mangium, Fabaceae). In Morehead area of Papua New Guinea subspecies randi has been recorded in tall mixed savanna.

Food and Feeding. A study offecal pellet contents from three localities, two on mainland of Northern Territory and one in Tiwi Islands, found the Brush-tailed Rabbit Rat to be primarily granivorous, with grass seeds in 58-74% of scats, leaves in 19-26%, plant stems in 6-13%, and insects in 1-5%; seeds were primarily of grasses, with perennial grass Alloteropsis semialata ( Poaceae) most important. A less extensive study of samples from Mitchell Plateau, in Kimberley region of Western Australia, also found seeds and leaf material in majority of scats, but invertebrate remains more abundant, with arthropods in 38% and termites in 13%. Stomachs of “a couple of animals” examined on Cobourg Peninsula in 1965 contained “green vegetable matter.” Intestinal cecum of the Brush-tailed Rabbit Rat is moderately large, suggestive of high leafy vegetal intake for at least part of each year.

Breeding. Studies on Cobourg Peninsula found breeding activity in July-August 1965 but none in February to early March 1966. Three pregnant females each carried two embryos. Studies on laboratory colonies of the Brush-tailed Rabbit Rat confirmed litter sizes of 1-4 (modally three) and documented a gestation period averaging 36 days in non-lactating females but up to 48 days when a litter is being suckled. Newborn young are large and develop rapidly, being well furred after one week of growth, and with open eyes at ¢.10-12 days, at which point they make loud distress calls when separated from the mother; for first ten days or more oflife young may be more or less permanently attached to the mother’s teats, after which they presumably remain in a nest while she forages; young were weaned at 20-21 days, when they weigh 35-40g; near-maximum weightis attained by about three months, and females are sexually mature at this time. Compared with other Australian members of Hydromyini, development of young Brush-tailed Rabbit Rats is particularly precocious, and onset of sexual maturity is also very rapid. Overall, the reproductive pattern suggests an opportunistic species with capacity rapidly to increase its population density under favorable conditions; on other hand, some wild individuals have survived into their third year, which suggests that such opportunities may not come around every year. Dens are usually in fallen logs or in tree hollows in eucalypts, bloodwood trees ( Corymbia, Myrtaceae), or she-oaks, with strong preference for rough-barked trees. In radio-tracking study by R. Firth, many individuals used more than one den site within a single tracking period of 4-17 days. They are also known to shelter in crowns of Pandanus palms.

Activity patterns. Nocturnal; this species’ proportionally large eyes suggest high visual acuity. Carpet pythons (Morelia spilotes) and a carnivorous marsupial, the Northern Quoll ( Dasyurus hallucatus), are its principal predators, but in the past it was also hunted by indigenous Australians. Granivorous diet of Brush-tailed Rabbit Rats implies that they spend considerable proportion of their time on ground, but field observations more typically involve animals that are climbing in treesof Pandanus palmsor, if they are on the ground, are close to treesand rapidly ascend when startled.

Movements, Home range and Social organization. Firth conducted radio-tracking studies at three sites in Northern Territory in 2000-2002, following 61 individuals. Mean home range size for all individuals pooled was estimated at 0-79 + 0-09 ha (using minimum convex polygon method, MCG) or 0-97 + 0-12 ha (using a fixed kernel method). Home ranges (MCG) were higher for males (1-1 + 0-15) than for females (0-45 + 0-06 ha), with no significant seasonal or inter-site contrasts. The tail brush is apparently erectile, and is expanded when an individual is excited or interested. D. Thomson, who maintained several wild-caught Brush-tailed Rabbit Rats in Northern Territory in 1940s, reported several vocalizations,including a “chirruping sound” uttered almost constantly by a ten-day old young and a “rasping, growling cry” made through the night by an adult. In the laboratory, males, females, and young will share a nest. This suggests that social bonding and tolerance are features of this species’ behavior, but there are no field observations suggesting any kind of regular social interaction apart from courtship, mating, and perhaps the rearingof young.

Status and Conservation. Classified as Vulnerable on The IUCN Red List. Confirmed recent records on Australian mainland are from Cobourg Peninsula and Kakadu National Park (Northern Territory) and from Mitchell Plateau and Prince Regent National Park (Kimberly region of Western Australia). In Kakadu National Park, where the Brush-tailed Rabbit Rat was formerly widespread and abundant, it appears now to be restricted to one small area. It has fared somewhat better on at least some offshore islands, with post-2000 records from Groote Eylandt and from both Melville and Bathurst Islands in Tiwi group, but a recent survey of Melville Island found evidence of significant recent decline. On Centre Island in Sir Edward Pellew Group, Northern Territory, a population first located in 1966 was not refound during numerous recent surveys. The two records from Papua New Guinea date from 1936 and 1972-1973, and recent survey work by S. Hamilton failed to detect the species in habitat similar to that around the two prior localities. Small number of historical records and recent specimens collected from surfaces of caves indicate that original range of the Brush-tailed Rabbit Rat extended across monsoonal tropics of Australia from Barkly Tableland in hinterland of Gulf of Carpenteria in the east to Dampier Land peninsula in the west. This area received very little early biological exploration, yet during early historical period the Brush-tailed Rabbit Rat was observed to be common in several locations within its range. This situation prevailed in at least some areas up to 1960s or later, after which the species appears to have undergone declines over a large area. Since monsoonal tropics of Australia support only low human populations and preserve continuous tracts of superficially intact natural habitats over very large areas, the cause of decline ofthis species and of many other species of native mammalis perplexing. Many potentially contributing factors have been nominated, and all may be involved, including habitat degradation caused by semiferal cattle, feral pigs, and feral water buffalo, predation by introduced animals (mainly feral domestic cats), and possibly novel wildlife diseases. Nevertheless, evidence increasingly points to changes in firing regimes as primary and most pervasive cause of the declines. Prior to European settlement, indigenous Australian people occupied every part of this landscape and they used small-scale, low-intensity fires to maintain a productive mosaic of vegetation communities at diverse successional stages. Through the past 100 years, increasingly large areas ofthe tropical landscape have been effectively depopulated, landowners congregating into more urban communities, and former regime of sporadic, low-intensity fires has been replaced by tendency for catastrophic, high-intensity dry-season fires that destroy fallen timber stocks, kill mature trees, and both change and homogenize the vegetation communities and render them far less suitable for the Brush-tailed Rabbit Rat. Somewhat paradoxically, complete cessation of burning is thought unlikely to restore populations of this murine,as it leads to a denser understory and a reduction of grasses that represent the species’ principal food. Recent study by H. Davies and coworkers on Melville Island produced compelling evidence that predation by feral cats is also a major contributor to decline of local populations of the Brush-tailed Rabbit Rat. Long-term survival ofthis species may rely on intensive landscape management to restore habitat heterogeneity, perhaps coupled with feral-cat control, and captive breeding and release programs.

Bibliography. Baverstock, Watts, Gelder & Jahnke (1983), Baverstock, Watts & Hogarth (1977), Breed (1997), Breed & Sarafis (1979), Breed & Taylor (2000), Burbidge & Woinarski (2016), Calaby & Keith (1974), Cramb & Hocknull (2010), Davies et al. (2017), Dickman et al. (2000), Firth, Brook et al. (2010), Firth, Jefferys et al. (2005), Firth, Woinarski, Brennan & Hempel (2006), Firth, Woinarski & Noske (2006), Flannery (1995b), Ford (2006), Gould (1842, 1858), Gray (1843), Kemper & Firth (2008), Kemper & Schmitt (1992), Lawes et al. (2015), Lidicker & Brylski (1987), Mahoney & Richardson (1988), Morris (2000), Morton (1992), Musser & Carleton (2005), Ogilby (1837 1838a), Start et al. (2007), Tate (1951), Tate & Archbold (1938), Thomas (1921j), Waithman (1979), Watts & Aslin (1981), Watts et al. (1992), Woinarski (2000), Woinarski et al. (2001).