718.

Australian Bush Rat

Rattus fuscipes

French: Rat de brousse / German: Australische SchwarzfulRratte / Spanish: Rata peluda de Australia Other common names: Allied Rat, Bush Rat; Western Swamp Rat (fuscipes), Southern Bush Rat (assimilis)

Taxonomy. Mus fuscipes Waterhouse, 1839,

“Australia, King George’s Sound.” Restricted by J. M. Taylor and B. E. Horner in 1973 to “ ‘Little Grove’ on Princess Royal Harbour, approx. 4 mi [= 6 km] south of Mount Melville, Albany, Western Australia, Australia.”

Rattus fuscipes is sister to all other Australian Rattus except R. leucopus, which is basal to this clade. Each of the recognized subspecies is morphologically and genetically distinct; although they can interbreed, they might may represent distinct species (especially coracius) with further research. Rattus f. assimilis might represent multiple subspecies. Four subspecies recognized, but subspecific taxonomy requires reassessment.

Subspecies and Distribution.

R.c.fuscipesWaterhouse,1839—SWWesternAustraliaaswellasvariousoffshoreIs .

R.c.asstmilisGould,1858—EVictoriaandSEQueenslandandsomeoffshoreIs .

R.c.coraciusThomas,1923—NEQueensland,includingHinchinbrook I.

R. c. greyi Gray, 1841 — SE South Australia and SW Victoria as well as various offshore Is including Kangaroo I.

Descriptive notes. Head-body 100-205 mm, tail 100-195 mm, ear 18-25 mm, hindfoot 30-40 mm; weight 50-225 g. The Australian Bush Rat is medium-sized and highly variable, with males larger than females. Pelage is soft and dense, with coarser black guard hairs throughout. Dorsum is gray-brown to reddish brown and blends into ventral pelage. Hairs are gray and translucent basally. Some island populations have lighter and redder dorsum, while populations in more humid regions are darker. Venter is light gray to buffy cream. Feet are light colored on mainland and dusky on Kangaroo Island and in western Australia. Ears are rounded, sparsely haired, and similar in color to dorsum; vibrissae are relatively short. Tail is ¢.100% of head-body length, nearly naked, and variably in color, ranging from brown to gray to blackish occasionally. Skull is elongated and relatively flat. Subspecies assimilis and coracius are larger; grey: and fuscipes are c.10-20% shorter and 30-40% lighter. In winter at high elevations and southern regions, body fat increases, weight decreases, and fur becomes more dense. Subspecies coracius tends to be more reddish brown dorsally and white ventrally, has lighter feet, and commonly has white blaze between ears; fuscipes generally is browner dorsally and gray ventrally, has darker feet, and lacks blaze between ears. Many species of cestodes (e.g. Bertiella, Choanotaenia, and Taenia), nematodes (e.g. Angiostrongylus, Contracaecum, Dipetalonema, Gongylonema, Paraustrostrongylus, Syphacia, and Trichosomoides), trematodes (e.g. Brachylecithum and Neodiplostomum), chiggers (e.g. Ascoschoengastia, Schoutedenichia, and Trombicula), ticks (e.g. Ixodes and Haemaphysalis), lice (Hoplopleura), fleas (e.g. Acanthopsylla, Bibikovana, Stephanocircus, and Xenopsylla), protozoans (e.g. Haemobartonella, Toxoplasma, and Trypanosoma), bacteria (e.g. Brucella, Leptospira, and Streptobacillus), and a staphylinid beetle ( Myotyphlus) have been recorded from the Australian Bush Rat—the most of any Australian rodent. There are five pairs of mammae: two pectoral and three abdominal (specimens from northern New South Wales have only one pectoral pair). Chromosomal complement is 2n = 38, FN = 60.

Habitat. Subalpine woodland, coastal scrub, coastal heath, eucalyptus forest, and tropical moist forest from sea level to elevations of 2210 m. Northern populations of Australian Bush Rats are found in more forested habitats, and southern populations are confined to drier regions. They rely on dense understory for shelter and cover from predators while foraging at night.

Food and Feeding. The Australian Bush Rat is selectively omnivorous, being highly insectivorous and herbivorous. In winter, diets mostly contain fungi, fibrous stems, leaves, and specific grasses and lilies. In summer, diet mostly contains insects, fruit, and seeds. The species is highly dependent on fungal mycorrhizae and leaf litter insects, which makes them highly susceptible to bush fires that can almost completely eliminate these foods for extended periods of time. Food is hoarded, and waterlogged items are occasionally retrieved, most commonly in times of food depravation.

Breeding. Australian Bush Rats reproduce year-round, but breeding is rare in winter, especially in southern parts of the distribution. Estrous cycles range from 4-5 (assimalis, with proestrus of 10-14 hours) to 5-3 (coracius, with proestrus of 24 hours). Postpartum estrus occurs c.41 hours after birth and lasts less than 24 hours. Females give birth by tucking their hindfeet under their body, tail to one side and forefeet used for support, and licking each young as it comes out. A male might be present during births, and in one instance, he helped with cleaning young and ate placenta, which is normally done by the female. Postpartum females are aggressive and can kill the male during postpartum heat. Gestation lasts 22-24 days (mean 22-8) and can be extended to 28-32 days by delayed implantation during lactation. Litters have 1-7 young in captivity and 1-8 young in the wild (mean four and five, respectively). Ovulation rates are higher in fuscipes and grey: (6-4-8-4) and lower in assimilis and coracius (4-9-5-4), with corresponding larger and smaller litter sizes. Young are born with eyes closed, pink and hairless, weighing c.4 g, and ¢.56 mm long. They have hair at c.12 days and walk at c.15 days; eyes do not open until 20 days old. They are probably weaned a little after opening their eyes at c.20-25 days. They become completely independentafter 4-5 weeks and are capable of reproducing in the wild at c.4 months; some individuals born in spring can breed before winter. Subadults disperse after they become able to. Males generally disperse much farther (762 m) than females (213 m) in Victoria, but in Queensland, they both reportedly traveled 365 m. They usually live ¢.12 months in the wild but up to 16 months in captivity.

Activity patterns. The Australian Bush Rat is nocturnal, generally foraging and moving around at night. Their peak activity pattern is bimodal, just after sunset and just before sunrise, although this can change with weather conditions. In Queensland, males moved (average c.183 m) around at night further than females (127 m). Movement of males during major breeding months was significantly farther than ofjuveniles and females. During fires, Australian Bush Rats are known to hide in their burrows, and after fires, they hide in ash because there is no vegetation for cover. Exploratory activity increases in summer. The Australian Bush Rat is terrestrial, although it will occasionally climb trees to reach food. Nests are made in burrows, and individuals will take refuge in hollow logs and rock crevices. Pathways connect various burrows, but they usually are inconspicuous except where vegetation is thick. Nest consists of main tunnel that descends 30-45 cm below the surface to nest chamber c.15 cm in diameter and lined with grass and other fibrous vegetation.

Movements, Home range and Social organization. Australian Bush Rats occur at densities of ¢.10 ind/ha, and highest densities occur in tropical forests. Females expand or retain their home ranges in spring; males vastly expand their home ranges or disperse. Female home ranges thus do not overlap, but male home ranges overlap multiple adjacent female home ranges. Australian Bush Rats can be rather aggressive toward conspecifics and are not gregarious. They make various sounds accompanying aggressive displays and non-aggressive behaviors, which include squeals, ultrasonic pipping, ultrasonic whistle, and coughing. On silent encounters, individuals might sniff each other, occasionally stretching their bodies. Copulation always occurs at night, is generally accompanied by allogrooming, and can occur (not always with ejaculation) even when a female is not in heat. Because their life span is short, near complete die offs of breeding individuals of the previous year can occur. During fires, populations decrease, and food availability also affects population size.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Australian Bush Rat has a relatively wide distribution and is common through most ofits distribution. It occurs in many protected areas. It is highly sensitive to habitat destruction, alteration, and degradation and is probably threatened by logging and mismanaged fire regimes and bushfires. It is considered an economic pest in cane fields.

Bibliography. Lindenmayer et al. (2005), Menkhorst & Knight (2010), Menkhorst et al. (2016), Musser & Carleton (2005), Peakall et al. (2006), Rowe et al. (2011), Stewart (1979), Taylor & Calaby (1988a), Taylor & Horner (1973), Tory et al. (1997), Van Dyck & Strahan (2008), Warneke (1971), Wood (1971).