Sminthopsis youngsoni, McKenzie & Archer, 1982

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 : 348

74.

Lesser Hairy-footed Dunnart

Sminthopsis youngsoni

French: Dunnart de Youngson / German: Wiisten-SchmalfuRbeutelmaus / Spanish: Raton marsupial pequefo de pies peludos

Other common names: Desert Dunnart

Taxonomy. Sminthopsis youngsoni McKenzie & Archer, 1982 ,

Edgar Ranges , 18° 50” S, 123° 05° E, Western Australia, Australia.

Numerous morphological and genetic studies have examined relationships among the Sminthopsinae . However, confusion remains among even generic-level placements within the group. Genetic phylogenies have consistently failed to support monophyly of the genus Sminthopsis with respect to Antechinomys and Ningaui . In recent research, there were three deeply divergent clades of Sminthopsis . The first clade supported S. longicaudata as sister to Antechinomys laniger . The second clade was composed of the traditional morphologically based Macroura Group: five Sminthopsis comprised a strongly supported clade that included S. crassicaudata , S. indi, S. macroura , S. douglasi , and S. virginiae . This clade of five dunnarts was a poorly supported sister to the three Ningaui species. 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 comprising the Murina supergroup). This large dunnart clade contained a clade including genetically distinct S. psammophila , S. youngsoni , and S. hirtipes . S. youngsoni was described based on specimens from the Great Sandy Desert by N. L. McKenzie and M. Archer, in 1982, just a year after Archer’s rigorous review of the genus Sminthopsis . Monotypic.

Distribution. C & W Australia, ranging through the subtropical arid regions of Western Australia, S Northern Territory, SW Queensland, and extreme N South Australia.

Descriptive notes. Head-body 6.6-7.1 cm,tail 6:2—6-8 cm; weight 8-5-12 g. Fur ofthe Lesser Hairy-footed Dunnart is brownish-yellow above and white below. Basal one-half of tail is typically slightly swollen. It is smaller than the similar Greater Hairy-footed Dunnart (S. hirtipes ), with a proportionally shorter tail, hindfeet, and ears in relation to body length. The Greater Hairy-footed Dunnart and the Lesser Hairy-footed Dunnart are distinguished from other dunnarts by their relatively broad feet, with granular footpads and soles covered in fine, silvery hairs. These hairs in the Lesser Hairy-footed Dunnart are short and sparse compared with those of the Greater Hairyfooted Dunnart.

Habitat. Various plant communities associated with reddish desert sand plains, sand dunes, and interdune swales, including open shrublands of Acacia (Fabaceae) , Thryptomene (Myrtaceae) , Grevillea (Proteaceae) , or Melaleuca (Myrtaceae) , often with sparse Owenia (Meliaceae) , Casuarina (Casuarinaceae) , or Eucalyptus (Myrtaceae) trees, over spinifex (7riodia spp., Poaceae ) hummock grasslands. In some places, these species are mixed with tussock or cane grasses such as Eragrostis sp. and Zygochloa sp. (both Poaceae ). One field study suggested that the strong positive association of capture rate of the Lesser Hairy-footed Dunnart with spinifex cover reflected the importance of spinifex in providing protection cover to foraging individuals. Exceptfor an early peak in capture rates of Lesser Hairy-footed Dunnarts in 1990 during a study when spinifex cover was low (5-6%), increasing capture rates since 1994 were associated with spinifex cover of more than 20%. Other observations suggested that although Lesser Hairy-footed Dunnarts forage indiscriminately with respect to habitat and predation risk, individuals nevertheless typically traveled within 1-2 m of spinifex hummocks; they flee into hummocks rapidly if disturbed.

Food and Feeding. There is no information available for this species.

Breeding. Young Lesser Hairy-footed Dunnarts are evidently born in spring. Pregnant females have been recorded in September; females with 5-6 pouch young have been caught in September—January. Independent juveniles have been captured in November-February. In April-June, populations typically include numerous subadults. In one long-term field study in the Simpson Desert, reproduction of Lesser Hairy-footed Dunnarts was strongly seasonal and confined largely to spring and summer. Indeed, with the exception of a single female recorded lactating in early August 1991, pouch development generally began in August each year. In most years of the study, lactation in females ceased by December; however, on three occasions, two lactating females were captured in March 1990, February 1998, and March 1999. Interestingly, two of these late-breeding females had been recorded with pouch young in spring the previous year; thus, they were raising their second litters for the season. No females were known to breed in the season of their birth because all matured at ¢.8 months of age. All females except one had six nipples; one had five nipples. Sixteen of 20 females with pouch young had a full complement ofsix young, two had five young, one had four, and one had three young. Sex ratio of pouch young in six litters was roughly equal. Young in five litters were toe-clipped in their mothers’ pouch; subsequently, one juvenile female was recorded on the same transect where her mother had been captured, and a juvenile male was recorded on an adjacent grid ¢.600 m away. Male Lesser Hairy-footed Dunnarts began to exhibit swollen cloacae and increased sternal gland activity in August each year and would evert their penis during handling. Mean scrotal width increased from autumn through winter, peaked in September, and then typically declined. Researchers concluded that males probably achieved reproductive age at more than eight months, with a body weight of more than 7-5 g and a scrotal width of more than 6 mm. Pulses of newly weaned Lesser Hairy-footed Dunnarts, some weighing as little as 2-2 g, entered the trappable population in November-December each year. Notably, young individuals were predominant in autumn populations and primarily responsible for higher capture rates in this season. Mostlikely, females would benefit from producing two litters in all years to maximize fitness, but they are prevented from doing so in some years because of inadequate food or other resources. As for many dasyurids, predictable onset of reproduction of the Lesser Hairy-footed Dunnart in winter and spring is likely timed to permit exploitation of invertebrate pulses in spring and summer.

Activity patterns. Lesser-Hairy-footed Dunnarts shelter in burrows by day, often those dug by spiders or dragon (agamid) lizards.

Movements, Home range and Social organization. In one comprehensive ten-year field study carried out on Ethabuka Station on the north-eastern edge of the Simpson Desert, western Queensland, an impressive 555 Lesser Hairy-footed Dunnarts were captured 713 times, giving a recapture success of 22:2%; more males (412) were captured than females (297). Peak rates of capture of an almost unprecedented (for Smanthopsis) 6-8 animals/ 100 trap nights occurred in 1990 and 1998. A prolonged period of lower captures was observed in 1991-1994. Capture rates were usually highest in autumn (March-May) and winter (June-August) and lower in spring (September— November). Capture rates of both sexes were equal in autumn, spring, and summer (December-February), but males were captured at a higher rate than females in winter. Astonishingly, the Lesser Hairy-footed Dunnart has been recorded moving up to 12 km at Ethabuka Station.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Lesser Hairy-footed Dunnart has a wide distribution, presumably has a large overall population, and occurs in a number of protected areas. It is apparently common in suitable habitat. There is no evidence of wide-scale population declines, and the Lesser Hairyfooted Dunnart is readily captured in pitfall traps. Relatively recent discovery of the Lesser Hairy-footed Dunnart probably reflects inappropriate collecting techniques used in the past. Predation from introduced domestic and feral cats and frequent, large-scale fires are localized threats, as they are for the majority of dasyurids. The Lesser Hairy-footed Dunnart has been recorded in protected areas including Karlamilyi National Park (= Rudall River National Park) in Western Australia and Uluru-Kata Tjuta National Park in Northern Territory.

Bibliography. Archer (1981a), Baverstock et al. (1984), Blacket, Adams et al. (2001), Blacket, Cooper et al.

(2006), Cole & Gibson (1991), Dickman et al. (2001), Haythornthwaite (2005), Krajewski et al. (2012), Letnic (2002), Masters (1993), McFarland (1992), McKenzie & Archer (1982), McKenzie & Cole (2008), McKenzie & Dickman (2008b).

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)

Distribution. C & W Australia, ranging through the subtropical arid regions of Western Australia, S Northern Territory, SW Queensland, and extreme N South Australia.