Dasycercus Blythi Research Articles

An investigation into the utility of eastern barn owl pellet content as a tool to monitor small mammal diversity in an arid ecosystem

AbstractConsidering several logistical limitations associated with live trapping in arid environments, owl pellet analysis provides a potentially useful alternative to estimate small mammal diversity. Owl pellet analysis has been used to estimate local small mammal diversity under the assumption that the method can reliably reflect the composition of local small mammal assemblages. However, the validity of owl pellet contents for use in ecological assessments has not been established. Thus, the present study aimed to determine the potential for eastern barn owl (Tyto delicatula) pellet analysis to improve the monitoring of small mammals in arid Australia. We analysed two ecological datasets from Pilungah Reserve on the northern boundary of the Simpson Desert in central Australia to assess their effectiveness for detecting expected small mammal species: 250 owl pellets collected from a known roosting site and 5 years of small mammal records from historical, long‐term trapping surveys. Species composition and detection probability of mammals varied depending on the method used. Owl pellet analysis returned higher species richness overall, while traditional trapping methods indicated a higher probability of detecting certain mammal species (e.g., the wongai ningaui Ningaui ridei, brush‐tailed mulgara Dasycercus blythi and the hairy‐footed dunnart Sminthopsis hirtipes). Importantly, analysis of owl pellets revealed two mammal species that had never been detected at the study site (dusky hopping mouse Notomys fuscus and Carpentarian false antechinus Pseudantechinus cf. mimulus). We suggest that owl pellet analysis could be particularly valuable when used as a precursor or in concert with traditional trapping to monitor and assist in the conservation of small mammal species in arid environments.

Taxonomic review of the genus Dasycercus (Dasyuromorphia: Dasyuridae) using modern and subfossil material; and the description of three new species

The genus Dasycercus (Dasyuridae: Dasyuromorphia) has a long and ongoing history of taxonomic uncertainty. Currently two species are recognized: Dasycercus cristicauda and Dasycercus blythi, with the previously named Dasycercus hillieri considered a junior synonym of D. cristicauda. This investigation integrates modern, historical and subfossil material from across Australia to provide the most comprehensive review of the genus to date. Cranial and dental morphological characters that enable phylogenetic and morphometric analysis of taxa are established. Linear discriminant analysis (LDA) and principal component analysis (PCA) of craniodental measurements, including from the type specimens of named taxa (D. cristicauda, D. hillieri and D. blythi), are used to assess the validity of each taxon. The results confirm the validity of D. cristicauda and D. blythi as species, but also reconfirm the validity of D. hillieri. As a result, much of the modern ‘D. cristicauda’ material is reassigned to D. hillieri. Three new taxa are proposed: Dasycercus woolleyae sp. nov., Dasycercus archeri sp. nov. and Dasycercus marlowi sp. nov. These six Dasycercus species are distributed across Australia’s arid zone and beyond. Based on prior investigations and the results of this taxonomic review, it is likely that only D. hillieri and D. blythi are extant. The identification of four likely extinct taxa marks the first recorded instance of modern extinction within the family Dasyuridae.Jake Newman-Martin [jake.newman-martin@student.curtin.edu.au], School of Earth and Planetary Sciences, Curtin University Kent St, Bentley, WA, 6102 Australia;Kenny J. Travouillon [Kenny.Travouillon@museum.wa.gov.au], Western Australian Museum, Collections and Research, Locked Bag 49, Welshpool DC, WA, 6986 Australia;Natalie Warburton [N.Warburton@murdoch.edu.au], Harry Butler Institute, Murdoch University, 90 South Street, Murdoch Western Australia 6150 Australia;Milo Barham [Milo.Barham@curtin.edu.au], School of Earth and Planetary Sciences, Curtin University Kent St, Bentley, WA, 6102 Australia;Alison J. Blyth [Alison.Blyth@curtin.edu.au], School of Earth and Planetary Sciences, Curtin University Kent St, Bentley, WA, 6102 Australia.

Population size, morphometrics and movement patterns of the brush-tailed mulgara (Dasycercus blythi): is predation by mammalian predators having an effect?

Worldwide predation by feral cats has caused severe declines in many animal species. Prior to extinction, threatening processes typically alter species behaviour, habitat use, survival and reproductive rates. By monitoring these parameters, we may be able to determine if feral cats are a significant threatening process to a species prior to extinction. We aimed to test whether feral cats are negatively affecting the population size, morphometrics and movement patterns of mulgaras (Dasycercus blythi) on the Matuwa Indigenous Protected Area, in the arid rangelands of Western Australia. We hypothesised that mulgaras, which inhabit a cat-free environment, would have a larger home range and denser population, and be in better condition than those that inhabited an adjacent area with a suppressed density of feral cats. We trapped (n = 64), and radio-tracked (n = 19) mulgara inside and outside an 1100 ha cat-free fenced enclosure on five occasions in 2012. Treatment (i.e. inside or outside the cat-free enclosure) was a significant variable for explaining variation in mulgara density. There was no significant difference in morphometrics or the home ranges of mulgara between the sexes or treatments. Head length, pes length and weight, as well as tail width and length, were significantly different between sexes and over time, suggesting that seasonal variation influences mulgara populations more than low levels of cat predation.

Class Conflict: Diffuse Competition between Mammalian and Reptilian Predators

(1) Diffuse competition affects per capita rates of population increase among species that exploit similar resources, and thus can be an important structuring force in ecological communities. Diffuse competition has traditionally been studied within taxonomically similar groups, although distantly related intraguild species are likely also to compete to some degree. (2) We assessed diffuse competition between mammalian and reptilian predators at sites in central Australia over 24 years. Specifically, we investigated the effect of dasyurid marsupial abundance on the diet breadth of three groups of lizards (nocturnal dietary generalists, diurnal dietary generalists and dietary specialists). (3) Nocturnal generalist lizards had progressively narrower diets as dasyurid abundance increased. The diet breadth of diurnal generalist lizards was unaffected by overall dasyurid abundance, but was restricted by that of the largest dasyurid species (Dasycercus blythi). Ant- and termite-specialist lizards were unaffected by dasyurid abundance. (4) Diffuse competition, mediated by interference, between dasyurids and nocturnal generalist lizards appears to have strong effects on these lizards, and is the first such between-class interaction to be described. Diffuse interactions may be widespread in natural communities, and merit further investigation among other disparate taxon groups that occur in the same ecological guilds.

Habitat use by the brush-tailed mulgara (Dasycercus blythi)

One of the largest remaining marsupial predators to persist across the Australian arid zone, despite increasing pressures, is the brush-tailed mulgara (Dasycercus blythi). Although D. blythi populations have declined since European settlement, they are currently considered stable, persisting in small, low-density isolated populations during periods of low rainfall. The main threat to the species is currently thought to be large introduced and feral predators. Through spool and line tracking, we examined how the species utilises its surroundings in relation to access to food resources and exposure to predators during a low-rainfall period. We found that D. blythi uses the open space between vegetation, a microhabitat that is known to support important prey species. We found that some individuals experiencing greater physiological demands consistently used resource-rich patches (such as termite mounds). We also identified the repeated use of great desert skink (Liopholis kintorei) burrows, which may provide access to prey items (such as young skinks), protection from predators and/or thermoregulation benefits. This study shows that D. blythi utilises several components in the landscape to increase access to reliable food resources and shows little active selection for areas that provide protection from predators.

Greater bilby burrows: important structures for a range of species in an arid environment

Greater bilbies (Macrotis lagotis) have been described as ecosystem engineers and their burrows are significant structures across an often featureless and harsh arid landscape. Remote cameras were deployed at bilby burrows to determine whether bilby burrows were important structures for other species. Cameras detected two mammal species, brush-tailed mulgara (Dasycercus blythi) and spinifex hopping mice (Notomys alexis), permanently occupying bilby burrows, and a further two species, short-beaked echidnas (Tachyglossus aculeatus acanthion) and sand goannas (Varanus gouldii), regularly using bilby burrows for shelter. An additional suite of 16 mammal, bird, reptile, amphibian and invertebrate species were detected interacting with bilby burrows. There was no difference in the number of species using disused or occupied bilby burrows, indicating that even disused bilby burrows are important structures for other species. We show that bilby burrows are used by a range of species and are analogous to the traditional, mostly North American, and commonly provided text book examples of the gopher tortoise and kangaroo rat. The disappearance of bilbies across at least 80% of their former range and thus the disappearance of their burrows as important structural resources in a harsh, arid environment may have had important consequences for a range of species.

Activity patterns and torpor in two free-ranging carnivorous marsupials in arid Australia in relation to precipitation, reproduction, and ground cover

It is generally assumed that in unpredictable environments, the use of daily torpor and its interaction with daily activity are largely dependent on environmental thermal conditions and resource availability. Using temperature telemetry, we compared the thermal biology and activity patterns of 2 species of mulgaras (Dasycercus blythi and D. cristicauda) at 3 sites of different habitat types in central Australia. The work compared a dry period with a wet period (resource pulse). The most obvious functional difference among populations was observed in the timing of the onset of activity, which began significantly earlier in dense unburned spinifex (on average 17.7 min before sunset) than in burned spinifex (4.6 min after sunset) or on gibber plains (21.8 min after sunset). However, although the seasonal expression of torpor differed significantly between males and females, torpor use as well as seasonal timing was similar among sites and periods despite differences in rainfall and habitat. It appears that predominantly reproductive activity governed torpor depth and duration in all measured populations and both species. Our data suggest that while the timing of activity is modulated by the amount of vegetation cover and thus protection from diurnal predators, torpor expression and winter reproduction in mulgaras are functionally linked and surprisingly more or less independent of apparent resource availability. Consequently, in mulgaras, daily torpor does not seem to be employed in response to immediate energy shortage but more likely to allow reallocation of energy and nutrients towards reproduction.

Why is the marsupial kaluta, Dasykaluta rosamondae, diurnally active in winter: Foraging advantages or predator avoidance in arid northern Australia?

The majority of animals have a specific activity rhythm over the 24 h daily cycle such that they can be categorised as either diurnal or nocturnal. This stability creates interest in understanding species that can invert their activity rhythm. The kaluta, Dasykaluta rosamondae, a small dasyurid marsupial endemic to northern arid Australia, is one such species. In contrast to most other dasyurid species and in fact most small mammals, the kaluta is almost exclusively diurnal in winter. To assess the potential benefits of diurnal activity we examined the diet and assessed potential predators and competitors. We identified 33 food categories including four classes of invertebrates, three classes of vertebrates and plant material. Diet was dominated by Coleoptera (beetles, 26.7% volume) and Formicidae (ants, 25.0% volume). We found no evidence that the prey base of kalutas differed as a consequence of diurnal activity. Likewise, diurnal foraging was probably not driven by competition. A likely explanation of diurnal activity in winter in this species is that it both allows temporal separation in activity from a significant predator, the brush-tailed mulgara, Dasycercus blythi, and reduces thermoregulatory foraging costs.

Cross‐cultural systematic biological surveys in Australia’s Western Desert

Summary We describe small‐scale biological surveys conducted by a collaboration of biologists and Traditional Owners designed to build scientific knowledge of the biota in remote desert regions of Western Australia. Importantly, while science driven (including systematic survey methods), the project also incorporated Indigenous Ecological Knowledge (IEK). In doing so, it has assisted with cross‐generational transfer and preliminary documentation of IEK in this region. Here, we describe a case study of surveys conducted with the Pila Nguru (Spinifex People) in the Spinifex Native Title Determined Area of the Great Victoria Desert. A total of 185 native plant species were recorded (representing 37 families and 94 genera). Only one individual of a weed species was recorded. Three plant species are new to science; Grevillea ilkurlka ms. Dicrastylis sp. ‘Ilkurlka’ and Gnephosis sp., with the first two of these species of conservation interest. The survey recorded 148 species of vertebrates; 72 birds, 21 mammals (of which six were introduced), 54 reptiles and one frog. Many animal names used by the Spinifex People were documented. The following animals that are of conservation interest were recorded: Itjarri‐itjarri (Southern Marsupial Mole, Notoryctes typhlops), Nganamarra (Malleefowl, Leipoa ocellata), Murrtja (Brush‐tailed Mulgara, Dasycercus blythi), and Princess Parrot (Polytelis alexandrae). We concur with previous authors that biological surveys, when cross‐cultural, can not only build scientific knowledge, but contribute to broader social goals of assisting Aboriginal people with cross‐generational transfer and documenting of IEK.

Population dynamics of Dasycercus blythi (Marsupialia: Dasyuridae) in central Australia: how does the mulgara persist?

Context Central Australia has been a graveyard for native mammals, with many small and medium-sized species becoming extinct or persisting in reduced geographical ranges in this region since the advent of European settlement. Species in the critical weight range (35–5500 g) have been affected most dramatically. Aims We compared the dynamics of two geographically distant populations of a medium-sized surviving desert mammal, the brush-tailed mulgara (Dasycercus blythi, ~100 g), and tested the hypothesis that this species’ persistence can be explained by its demographic plasticity. Methods Paired sampling grids, each 31.5 ha, were set up in the Tanami Desert on the northern edge of the species’ geographical range and near Uluru Kata Tjuta National Park (UKTNP) on the southern boundary. Animals were live-trapped every 3 months between 1992 and 1995, and estimates made of population size, residency, reproduction, bodyweight and tail width; the latter was used as an index of condition. Key results The UKTNP site supported a larger population of D. blythi than did the Tanami Desert site. In both areas, the population fluctuated annually, declining during the breeding season (June to October) and increasing again following the influx of juveniles in spring. Females had one litter per year, with a median and maximum litter size of six; births in the Tanami occurred in July, at least a month earlier than they did at UKTNP. Bodyweights and tail widths peaked before breeding and then declined until spring, with animals retaining better body condition in the Tanami than at UKTNP. In both regions, individuals were resident for 1–2 years; daughters remained near their mother’s home range but males moved to other areas. Conclusions The results provided little support for our initial expectation that populations of D. blythi would behave differently in disparate parts of the species’ geographical range, and suggested instead that this mulgara exhibits a predictable life history, with limited demographic flexibility. Implications The persistence of D. blythi in central Australia is most likely a result of its striking flexibility in use of food resources, its ability to enter torpor and to tolerate large declines in bodyweight and condition, and its propensity to dig deep burrows. We suggest that these attributes buffer mulgaras from the impacts of introduced predators that have contributed to extinctions of other medium-sized marsupials, and from climatic and resource uncertainties that shape the dynamics of many smaller desert mammals.

Spatial dynamics of small mammals in central Australian desert habitats: the role of drought refugia

Populations of small mammals often fluctuate dramatically in arid environments, persisting at very low density during drought and erupting briefly but dramatically after rain. We selected 3 species that exhibit such boom and bust dynamics in spinifex grassland in the Simpson Desert, central Australia, and asked how they survive prolonged dry periods when they are scarce or absent from the trapping record. We postulated that animals persist by retreating to small patches of open woodland that are embedded within the grassland matrix and predicted that these patches would provide more food and shelter for small mammals than the surrounding grassland during dry periods but not at other times. We also predicted that capture rates and activity of the study species would be higher, and risk of predation lower, in the woodland than in the grassland during drought, and that after heavy rain the rate of return of small mammals to spinifex grassland would be correlated with proximity to patches of woodland. Sampling provided partial support for these predictions. Some food resources (seeds) were more abundant in woodland patches irrespective of environmental conditions, but others (invertebrates) showed no clear pattern; shelter resources were mostly invariant between habitats and times. Of the 3 study species, only the sandy inland mouse (Pseudomys hermannsburgensis) behaved largely as we had anticipated, but even this species was not confined to woodland during droughts. Both the spinifex hopping-mouse (Notomys alexis) and brush-tailed mulgara (Dasycercus blythi) continued to use grassland more than woodland during drought and nondrought periods, although N. alexis showed a tendency to increase its activity in woodland during dry conditions. Trappability remained relatively constant among species, habitats, and times, indicating that the temporal patterns of habitat use we uncovered were real and not artifacts of changes in animal behavior or susceptibility to capture. We conclude that woodland patches contribute importantly to the persistence of P. hermannsburgensis during droughts, whereas N. alexis and D. blythi either use other unidentified refugia at such times or occur at such low densities in grassland habitat that their chances of being captured are very small.

Habitat use, population dynamics and species identification of mulgara, Dasycercus blythi and D. cristicauda, in a zone of sympatry in central Australia

Dasycercus cristicauda and Dasycercus blythi are significant mesopredators in arid Australia and both species are threatened nationally. We investigated size dimorphism, habitat use, and population dynamics of sympatric populations during a low rainfall period in central Australia and examined congruence between morphological and molecular methods of species identification. Our molecular analyses confirmed the presence of two Dasycercus species in sympatry and showed that the descriptions of Woolley (2005) allowed confident identification of the two species in the field. We captured 23 D. cristicauda and 55 D. blythi over 39 months on 20 monitoring plots and another 49 survey sites stratified across five habitat types within a 7000 km2 area. Both species showed sexual dimorphism in body mass with males being significantly heavier. The species typically occupied non-overlapping habitat; D. cristicauda was restricted to sandridges (n = 4 sites) with an understorey dominated by spinifex (Triodia), whereas D. blythi occupied sand plain and gibber plain, the latter being a new habitat for the species. Capture rate of D. cristicauda peaked in autumn-winter 2008 and winter 2009. D. blythi exhibited similar variability with peaks in winter 2009 and summer-autumn 2010. We consider that the relatively low abundance of each species during low rainfall periods makes them vulnerable to predation by feral house cats and European red foxes.

Vertebrate diet decreases winter torpor use in a desert marsupial

One of the energetic benefits of daily torpor over prolonged hibernation is that it enables animals to regularly forage and, therefore, replenish food reserves between bouts of torpor. However, little is known about the diet of predators undergoing torpor or whether differences in prey composition among individuals influence torpor characteristics. Here, we test the hypothesis that prey composition affects winter torpor use and patterns of a population of carnivorous marsupial, the brush-tailed mulgara (Dasycercus blythi), in the Great Sandy Desert, Australia. Mulgaras in the study population captured a wide range of prey including vertebrates (mammals, reptiles, birds), seven insect orders, spiders and centipedes. The proportion of vertebrates in the diet was negatively correlated with both frequency of torpor use and maximum bout duration. This variation in torpor use with diet can be explained by the higher energetic content of vertebrates as well as their larger size. Even assuming uniform intake of prey biomass among individuals, those that subsisted on an invertebrate-dominated diet during winter apparently suffered energetic shortages as a result of the scarcity of invertebrate taxa with high energy content (such as insect larvae). Our study is the first to demonstrate a link between diet composition and daily torpor use in a free-ranging mammal.

Thermal Biology, Torpor, and Activity in Free‐Living Mulgaras in Arid Zone Australia during the Winter Reproductive Season

Little is known about the energy conservation strategies of free-ranging marsupials living in resource-poor Australian deserts. We studied activity patterns and torpor of free-living mulgaras (Dasycercus blythi) in arid central Australia during the winter of 2006. Mulgaras are small (approximately 75 g), nocturnal, insectivorous marsupials, with a patchy distribution in hummock grasslands. Mulgaras (six males, three females) were implanted intraperitoneally with temperature-sensitive transmitters and monitored for 6-55 d. Temperature profiles for different microhabitats and the thermal properties of soil and a number of burrows were also measured. Air temperature ranged from -3 degrees C at night to 30 degrees C during the day. Although burrows buffered temperature extremes, the thermal diffusivity of the sandy soil was high, and many burrows were shallow. Hence, soil and burrow temperatures averaged about 15 degrees C. The activity of mulgaras was often restricted to a few hours after sunset, before they retired into their burrows. Mulgaras employed torpor frequently, often entering torpor during the night and arousing around midday, with arousals occurring later on cooler days. Shallow burrows allowed cooling below mean T(soil). Consequently, body temperatures as low as 10.8 degrees C were observed. The longest torpor bout was 20.8 h. Torpor patterns changed seasonally and differed between males and females. From June to August, females entered torpor almost daily despite mating and gestation, but from the end of the gestation period onward, they remained normothermic. In contrast, males showed only shallow and short torpor during the mating season, but from mid-July, a transition to more frequent and deeper torpor resembling that of females was observed. Apparently, in both sexes, the reproductive effort entails energetic costs, but torpor, as an energy-saving mechanism, and reproduction are not exclusive in mulgaras. In a resource-poor environment during the least productive part of the year, frequent torpor seems to provide the means to compensate for the increased energetic costs associated with reproduction.

Spatial ecology of the mulgara in arid Australia: impact of fire history on home range size and burrow use

AbstractKnowledge about the spatial ecology of small mammals in relation to fire history in arid zones in general and Australia in particular is limited. Here, we report data on the spatial ecology of the brush‐tailed mulgara Dasycercus blythi in the hummock grasslands of Uluru – Kata Tjuta National Park during winter 2006, the beginning of the breeding season for this species. About 73% of the study area had been burnt in 2002 and spinifex cover was sparse. Mulgaras Marsupialia: Dasyuridae (six males and three females) were implanted with radio‐transmitters and monitored daily for between 6 and 55 days. All mulgaras appeared to use defined home ranges, which overlapped extensively with those of several neighbours. Spatial overlap occurred between as well as within sexes. On average, males (25.5 ha) occupied significantly larger home ranges than females (10.8 ha). Mulgaras used a number of burrows within home ranges and several were used by more than one individual. Moreover, occasionally, two individuals used the same burrow simultaneously. Home ranges and burrows encompassed both mature spinifex Triodia basedowii and open regrowth areas and mulgaras did not exhibit a significant preference for either habitat type. However, three males were killed by introduced‐predators and they all lived predominantly in the open regrowth area. We conclude that mulgaras do not select the dense cover of mature spinifex habitat, and might be subjected to increased risk from introduced predators, especially following fire.

Studies on the crest-tailed mulgara Dasycercus cristicauda and the brush-tailed mulgara Dasycercus blythi (Marsupialia: Dasyuridae).

Two genetically distinct Dasycercus are correctly named D. cristicauda (crest-tailed mulgara) and D. blythi (brush-tailed mulgara). Some publications reporting observations have mistakenly referred to D. cristicauda when the animal was really D. blythi. Based on the source of the material I document the species on which the observations were made in all publications known to me.

The species of Dasycercus Peters, 1875 (Marsupialia: Dasyuridae)

Woolley, P.A. 2005. The species of Dasycercus Peters, 1875 (Marsupialia: Dasyuridae). Memoirs of Museum Victoria 62(2): 213–221. Two species of Dasycercus (mulgaras) are recognised. They can be distinguished by the form of the tail, the number of upper premolar teeth in each jaw and, in the female, by the number of nipples in the pouch. Dasycercus blythi has a non-crested tail, two upper premolars (and a diastema between P 2 and M 1 ) and six nipples; D. cristicauda has a crested tail, three upper premolars (the third very small and sometimes present on one side only) and eight nipples. Both species have a wide geographic range in the arid zone of Australia, and overlapping distributions. The identity of specimens previously referred to D. cristicauda in the W. B. Spencer collection of Museum Victoria has been reassessed and both species found to be represented.