Sminthopsis crassicaudata (Gould, 1844)

Russell A. Mittermeier & Don E. Wilson, 2015, Dasyuridae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 232-348 : 337-338

60.

Fat-tailed Dunnart

Sminthopsis crassicaudata

French: Dunnart a grosse queue / German: Dickschwanz-SchmalfuRbeutelmaus / Spanish: Raton marsupial de cola gruesa

Other common names: Fat-tailed Marsupial Mouse

Taxonomy. Phascogale crassicaudata Gould, 1844 ,

Williams River , Western Australia, Australia.

A recent extensive genetic phylogeny of the Sminthopsinae failed to support monophyly of the genus Sminthopsis with respect to Antechinomys and Ningaui . Researchers resolved three deeply divergent clades of Sminthopsis ; in the first clade, S. longicaudata was sister to A. laniger . The second clade was composed of the traditional morphologically based Macroura Group: five Sminthopsis comprised a strongly supported clade, which included S. crassicaudata , S. bindi , S. macroura , S. douglasi , and S. virgimiae. This clade of five dunnarts was a poorly supported sister to the three species of Ningaui (N. nidei, N. timealeyi , and N. yvonneae). The combined clade of five Sminthopsis and three Ningaui was positioned as a poorly supported sister to a well-supported clade containing the remaining species of Sminthopsis (13 species in the Murina Group). Genetically, S. crassicaudata is strongly positioned within the Macroura Group as sister to a clade containing S. bindi , S. macroura , S. douglasi , and S. virginiae . Two forms have been recognized in recent genetic analyses: one in south-eastern Australia and the other in central and western regions. Two subspecies have been described on the strength of morphology, crassicaudata and centralis, but importantly the morphological classification does not reflect distribution of the major genetic subdivisions. Studies of mtDNA and allozymes (protein electrophoresis) of more than a decade ago have shown two genetic groups: one restricted to south-eastern Australia (Victoria and south-eastern South Australia) and the other in the remainder of the distribution (South Australia, western New South Wales, western Queensland, southern Northern Territory, and southern Western Australia). This finding implies that populations’ genetic boundaries do not concord with distributions of nominate crassicaudata and centralis based on morphology. Several morphological characters, such as tail length, ear length, and dorsal fur color and reflectance, previously used to distinguish morphological subspecies, show clinal variation from north to south; this has led some authors to question their subspecific distinctions. More taxonomic work is required to clarify intraspecific relationships. Two subspecies recognized.

Subspecies and Distribution.

S.c.erassicaudataGould,1844—lessaridareasofWesternAustralia,Queensland,SouthAustralia,NewSouthWales,andVictoria.

S. c. centralis Thomas, 1902 — arid C Australia.

Descriptive notes. Head—body 6-9 cm, tail 4-7 cm; weight 10-20 g. The Fat-tailed Dunnart is immediately recognizable by its large ears and eyes and by a swollen tail that is much shorter than that of the Stripe-faced Dunnart (S. macroura ). Throughout its distribution, the Fat-tailed Dunnart shows considerable variation in external morphology, including coat color, body size, ear length, and tail length. Tail length is slightly shorter than head-body length in northern populations but markedly less than head-body length in southern populations. Interdigital (between toes) pads of hindfoot have uniformly fine granules but tend toward development of midline rows ofslightly enlarged granules in northern populations.

Habitat. Variety of habitats, including open woodland, low saltbush ( Atriplex spp. ) and bluebush ( Maireana spp. ) shrublands, tussock and spinifex (7riodia spp., Poaceae ) grasslands on clay or sandy soils, gibber (desert pavement) plain, and farmlands in southern regions. Distribution of Fat-tailed Dunnarts extends from relatively moist regions near the southern coast of Australia through the arid inland to inhospitable plains of the Lake Eyre Basin.

Food and Feeding. The Fat-tailed Dunnart will use cover of night to forage on the ground in bare open areas. Generally speaking, insects and other invertebrates form the bulk of the diet, with juicy prey such as cockroaches and spiders being preferred during drought periods and energy-rich beetles at other times. Small vertebrates are taken only rarely and appear to be hunted using both sight and sound. Because enough water is obtained from these foods, the Fat-tailed Dunnart does not need to drink. Characteristically, fat tails function as an extra energy reserve that tends to be depleted during winter. A recent study examined diets of Fat-tailed Dunnarts at a site in western New South Wales. Twenty-four fecal samples from eight Fat-tailed Dunnarts contained eight invertebrate taxa. Spiders ( Araneae ) were the main prey, comprising 53% of invertebrates consumed. Hymenoptera (mainly ants) and Orthoptera (mainly crickets) were also heavily preyed on. Beetles ( Coleoptera ) were an important prey taxon (24%). Cockroaches (Blattodea) made up less than 1% of the prey. One fecal sample contained mammalian hair, but this was presumably the result of grooming.

Breeding. Female Fat-tailed Dunnarts give birth to 8-10 young; an average of five young survive until weaning at c.10 weeks. Breeding takes place in July-February. The female has a well-developed pouch containing 8-10 teats. Sufficient young are usually born to occupy all teats. Individuals reared in the laboratory may attain sexual maturity at c.5 months of age, but there is no evidence of breeding this early in the wild. In an experiment conducted in captivity, female estrus was detected by the presence of epithelial cells in urine on eight occasions between late July and mid-November. Spermatozoa were seen in urine of females on four occasions. Two female Fat-tailed Dunnarts copulated under shelters with one of the younger males in August. Seven litters of 1-8 young ensued, but the three females that produced large litters in August failed to rear their young to weaning. Young were progressively lost between 35 and 47 daysin individual litters. The female with a single young in Septemberlost it within three days. She produced a second litter of four, but it too was lost within six days; she again was in estrus in mid-November but failed to produce a third litter. Two female Fat-tailed Dunnarts produced second litters in October and were still rearing them when the experiment ended in November. Young in one litter were then 45 days old, and those in the otherlitter were 30 days old. In wild-caught females, estrus was not detected before late September or early October and then in only two of the three surviving females. Epithelial cells were seen in urine of both females and spermatozoa in one. Both of these wild-caught females produced litters of nine young in October.

Activity patterns. Fat-tailed Dunnarts are nocturnal. They avoid temperature extremes by sheltering in nests of grass or other dried plant material constructed beneath logs or rocks; in arid regions, they shelter within deep cracks in the soil. In autumn and winter, groups of Fat-tailed Dunnarts will frequently huddle together in communal nests throughout the day, conserving energy by sharing body heat. When food becomes hard to find, individuals regularly enter torpor. One captive study showed that when Fat-tailed Dunnarts were offered unpredictable levels of daily food, frequency of daily torpor and length of bouts increased compared with individuals offered food ad libitum.

Movements, Home range and Social organization. No long-term bonds are formed between parents or among mother and young. The Fat-tailed Dunnart typically nests alone during the breeding period (August—-March), but up to 70% of individuals share nests in groups of 2-8 individuals during the non-breeding period (April-July). These nest-sharing groups are not permanent; they appear to be random aggregations of individuals. Most nest-sharing during the breeding period involves pairs consisting of a male with an estrous female. Males and females have large, overlapping home ranges during breeding and non-breeding periods. Males appear to move their nest sites more frequently than females. Home ranges of individuals are spatially unstable; they are perhaps most accurately described as “drifting” home ranges. The only individuals that become territorial are breeding females; in such cases, females will defend only a small area around their nests. Males do not appear to defend their home ranges at all. A recent study examined home range and movements of Fat-tailed Dunnarts in western New South Wales. They chose resting sites within a relatively small nesting range; however, there could be several spatially discrete nesting ranges within individuals’ larger home ranges. Over several days and weeks, these nesting ranges are used with high site fidelity because individuals frequently reuse specific resting sites within this area. Yet, how often an individual returns to previous nesting ranges and what factors cause it to shift locations are unknown.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Fattailed Dunnart has a wide distribution, presumably has a large overall population, occurs in a number of protected areas,is tolerant of habitat modification, and does not face any major conservation threats. Fat-tailed Dunnarts appear to be common, even in degraded and agricultural areas. Populations in moister parts ofits distribution are relatively stable, but in arid regions, densities appear to fluctuate according to rainfall and consequent supply of invertebrate prey. In stark contrast to most other dasyurids, the Fat-tailed Dunnart has probably actually increased in distribution following clearing of land by European settlers. This is because it has a preference for open grasslands and low shrublands; thus, it has been able to inhabit farmlands after modification of forests and scrub in south-eastern and south-western Australia. Fat-tailed Dunnarts may be exposed to 1080 poison during baiting of Dingoes (Canis lupus dingo) with fresh meat baits. In one study, a group of species of Sminthopsis was conditioned to feed freely on meat in the laboratory, but when they were offered meat poisoned with 1080, their intake became significantly reduced, and they vomited. Some of these individuals refused to eat meat altogether even when a choice of poisoned and non-poisoned meat was presented to them. Fewer individuals died after eating poisoned meat than expected from the median lethal dose (LLD50) estimated by a standard technique of oral dosing with 1080 in water. Loss of appetite and aversion to taste and smell of meat containing 1080 were proposed as possible reasons for low intake of poisoned meat.

Bibliography. Archer (1981a), Baverstock et al. (1984), Blacket, Adams et al. (2001), Blacket, Cooper et al. (2006), Burbidge, Robinson, Ellis et al. (2008), Cooper, S.J.B. et al. (2000), Krajewski et al. (2012), Morton (1978a, 1978b, 1978c), Morton & Dickman (2008a), Munn et al. (2010), Read (1984a, 1987c), Sinclair & Bird (1984), Thomas (1888b), Warneke et al. (2012), Woolley & Watson (1984).

Figures

56. Kangaroo Island Dunnart (Sminthopsis aitken), 57. Chestnut Dunnart (Sminthopsis archer), 58. Kakadu Dunnart (Sminthopsis bindi), 59. Butler's Dunnart (Sminthopsis butleri), 60. Fat-tailed Dunnart (Smunthopsis crassicaudata), 61. Little Long-tailed Dunnart (Sminthopsis dolichura), 62. Julia Creek Dunnart (Smunthopsis douglasi), 63. Gilbert's Dunnart (Sminthopsis gilbert), 64. White-tailed Dunnart (Sminthopsis granulipes), 65. Grey-bellied Dunnart (Sminthopsis griseoventer), 66. Greater Hairy-footed Dunnart (Smunthopsis hirtipes), 67. White-footed Dunnart (Sminthopsis leucopus), 68. Greater Long-tailed Dunnart (Sminthopsis longicaudata), 69. Stripe-faced Dunnart (Sminthopsis macroura), 70. Common Dunnart (Sminthopsis murina), 71. Ooldea Dunnart (Sminthopsis ooldea), 72. Sandhill Dunnart (Sminthopsis psammophila), 73. Red-cheeked Dunnart (Sminthopsis virginiae), 74. Lesser Hairy-footed Dunnart (Sminthopsis youngsoni)

Subspecies and Distribution. S.c.erassicaudataGould,1844—lessaridareasofWesternAustralia,Queensland,SouthAustralia,NewSouthWales,andVictoria. S. c. centralis Thomas, 1902 — arid C Australia.