Southern Brown Bandicoot Isoodon Obesulus Research Articles

Fox control and fire influence the occurrence of invasive predators and threatened native prey

AbstractIt can be challenging to distinguish management impacts from other population drivers, including ‘natural’ processes and co-occurring threats. However, disentangling processes is important, particularly when management may have unintended consequences, such as mesopredator release. We explored the effects of long-term, broadscale poison-baiting programs on the distribution of red foxes Vulpes vulpes (targeted invasive predator), feral cats Felis catus (unmanaged invasive competitor) and two of their threatened native prey in two fire-affected regions of south-eastern Australia. We synthesised data from 3667 camera-trap deployments at 1232 sites (172,052 trap-nights), combining experimental manipulation of foxes and fire with space-for-time approaches. Fox control effectiveness—in terms of decreased probability of fox occurrence and increased probability of prey occurrence—depended on the duration and intensity of the poison-baiting program. The effects of fox control on prey occurrence also varied between the two native prey species: fox control was strongly beneficial to the long-nosed potoroo Potorous tridactylus but had no measurable effect on southern brown bandicoot Isoodon obesulus occurrence. Feral cat occupancy tended to be higher in landscapes with long-term fox control, although we found no effect of fox-bait density on fine-scale cat occurrence. Time since fire (0–80 years) was associated with the occurrence of each study species, but its association with invasive predators also differed among vegetation types. Invasive predators and altered fire regimes are key, often overlapping, biodiversity threats. Our work highlights the importance of fine-scale monitoring and consideration of multiple drivers in distribution models to develop effective, tailored conservation strategies.

Selection, characteristics, and frequency of use of shelter sites by the Southern Brown Bandicoot Isoodon obesulus obesulus and the Southern Long-nosed Bandicoot Perameles nasuta in a post-fire landscape

ABSTRACT Dense ground cover and understory can be important as diurnal shelter for terrestrial mammals. Fire can lead to the short-term removal of much of this shelter. Here, we report on the shelter site selection of the Southern Brown Bandicoot Isoodon obesulus obesulus and Long-nosed Bandicoot Perameles nasuta eight months after a wildfire. We analysed the number of shelters, frequency of shelter use, nest size, and shelter site microhabitat. Southern Brown Bandicoots used significantly more shelters than Long-nosed Bandicoots. Both species preferred to use shelters with significantly lower levels of transmitted light than matched control areas. Within the burnt landscape, Southern Brown Bandicoots located their refuges under regrowth eucalypts, whereas Long-nosed Bandicoots showed no preference for any microhabitat. Southern Brown Bandicoots built nests significantly higher above ground than Long-nosed Bandicoots. Nests built in more dense and darker microhabitats were significantly taller than those built in more open habitats. Following fire, the Southern Brown Bandicoot required a more dense groundcover to conceal its taller nests and was able to take advantage of regenerating mallee eucalypts for shelter. Land managers need to be aware that hazard reduction burning in coastal woodland and heath will temporarily deprive Southern Brown Bandicoots of diurnal shelter sites and should, therefore, where practicable, retain patches of unburnt dense undergrowth to ensure a mosaic of different aged habitat and habitat structure.

Elucidating Patterns in the Occurrence of Threatened Ground-Dwelling Marsupials Using Camera-Traps.

Simple SummaryBeing able to effectively monitor the continued plight of highly vulnerable animals against management efforts over time is critical for their conservation. In south-eastern New South Wales, Australia, we used a camera trapping array to collect baseline information about patterns of occurrence of three threatened native ground-dwelling marsupials of conservation interest: the long-nosed bandicoot (Perameles nasuta), long-nosed potoroo (Potorous tridactylus) and southern brown bandicoot (Isoodon obesulus). Over a four-year period, detections of the two bandicoots were more erratic and less predictable than that of the potoroo, resulting in higher uncertainty about occupancy estimates and adequacy of sampling effort. The detection probability of each bandicoot species and that of the potoroo differed variously with structural complexity of vegetation. Detection probability of the southern brown bandicoot was highest where ground cover was most dense and shrub cover most open. The reverse pattern was found for the long-nosed bandicoot. Finally, the detection probability of the long-nosed potoroo was highest where ground and shrub cover was densest. Future camera trapping monitoring efforts need to take better account of these nuances and be flexible to including additional sampling for at least the two bandicoots. In short, when it comes to monitoring approach, one size doesn’t fit all.Establishing trends in endangered fauna against management efforts is a key but often challenging enterprise. Camera-traps offer a new and literal window into monitoring many different mammalian species. Getting it right demands seeking baseline information about how often target species interact with these devices, prior to setting a long-term monitoring strategy. We used a camera-trap array to collect detection data on three species of threatened ground-dwelling marsupials in south-eastern mainland Australia. Over a four-year period, occupancy estimates for two species of bandicoot (southern brown bandicoot Isoodon obesulus and long-nosed bandicoot Perameles nasuta) and a single species of rat-kangaroo (long-nosed potoroo Potorous tridatylus) were generated. These estimates were variously robust depending on visitation history, but nevertheless indicated persistence of these rare and otherwise under threat species. Detection probability for each species differed between study areas, type of management and with complexity of ground and shrub vegetation cover. The relationship between detection and vegetation structure dictated that survey effort was only robust where conditions were optimal for a given species. Outside of that further survey effort would be required to have confidence in survey outcome. In the future this would demand a different sampling strategy, be that through lengthening survey time or adding additional camera units at sites.

Life in linear habitats: the movement ecology of an endangered mammal in a peri‐urban landscape

AbstractAnimal movement can be significantly altered in human‐dominated landscapes such as urban and peri‐urban areas, where habitat is often fragmented and/or linear. Knowledge regarding how wildlife respond to anthropogenic change is vital for informing conservation efforts in such landscapes, including the design of nature reserves and wildlife corridors. To better understand how threatened species persist and behave within human‐dominated landscapes, we examined the home range and space use of the nationally endangered southern brown bandicoot Isoodon obesulus obesulus in peri‐urban Melbourne, Australia’s second‐largest city. Specifically, we examined whether: (1) bandicoots were confined to linear strips of remnant vegetation or also made use of the broader highly modified landscape matrix; (2) the configuration of the linear vegetated strips affected home range shape; and (3) home range area differed between bandicoots living in linear strips and those in larger remnant habitat patches. We found that: (1) 71% of adult males and 33% of adult females used the matrix, but non‐dispersing juveniles were entirely confined to the linear strips; males also travelled greater distances into the matrix (away from the vegetated strips) than females; (2) bandicoots had longer home ranges in narrower strips and males had longer home ranges than females; and (3) home range area for both sexes was smaller in linear strips than has been recorded in other studies in larger remnant habitats. Our study highlights the importance of retaining narrow, fragmented and modified vegetation to accommodate threatened biodiversity within human‐dominated landscapes, but suggests the surrounding matrix may also offer important resources for adaptable species, such as bandicoots. Supporting off‐reserve conservation of biodiversity in novel ecosystems is increasingly pertinent in our rapidly urbanizing world.

Factors affecting the use of fauna underpasses by bandicoots and bobtail lizards

AbstractThe construction of fauna underpasses is becoming increasingly common in road construction projects. However, factors that affect their use by native fauna in Australia are still largely unknown. We monitored 10 fauna underpasses for 13 months to determine factors affecting their use by southern brown bandicoots Isoodon obesulus fusciventer and western bobtail lizards Tiliqua rugosa rugosa. We trapped around each underpass five times to determine the size of the populations of these two species. Bandicoots and bobtail lizards were marked with passive implant transponders (PIT) and PIT readers and motion‐activated infrared cameras recorded the number of crossings and the number of individuals that used each underpass. For bandicoots the mean weekly frequency of use corrected for population size and the proportion of the marked population that used each underpass were modelled against factors hypothesized to impact underpass use using generalized linear models. These were underpass length, cross‐sectional area, vegetation cover at the entrances, presence or absence of logs and branches in the underpass (furniture), use by introduced predators and time since construction. Underpass length was negatively correlated with the frequency of use by bandicoots and time since construction was negatively correlated with the proportion of the population that used the underpasses. For western bobtail lizards none of the factors tested were strongly correlated with the frequency of use, or the proportion of the population that used the underpass. Based on these results, we recommend that the length of underpasses be kept to a minimum, possibly through the use of vegetated median strips allowing shorter underpasses to connect habitat on either side of the road. This would likely result in greater use than one long underpass spanning the entire width of the road.

Comparative diets of the chuditch, a threatened marsupial carnivore, in the northern and southern jarrah forests, Western Australia

The chuditch Dasyurus geoffroii was the largest carnivorous marsupial across most of its former range, from which it has largely disappeared. Published dietary information is unavailable from much of the species' current range, thus limiting our ability to manage the species or to assess its potential impacts on prey populations. Using analysis of scats, we describe and compare the diets of chuditch in the northern (NJF) and southern (SJF) jarrah forests, Western Australia. Mammals and invertebrates dominated the diet in both areas. However, reptiles and birds were also consumed frequently, confirming the chuditch as a generalist predator. A high proportion of large mammals in the diet suggests that it may also be a frequent scavenger. Although diet was broadly similar in both study areas, some differences were apparent. For example, chuditch in the SJF consumed more brushtail possums Trichosurus vulpecula hypoleucus and southern brown bandicoots Isoodon obesulus fusciventer. Seasonal variation in the diet was also apparent, with reptiles and invertebrates being consumed more frequently in the warmer months. A more detailed understanding of chuditch diet in different areas will be essential to assess likely interactions with introduced predators as well as with native prey. © 2010 The Authors. Journal of Zoology

Do cat restrictions lead to increased species diversity or abundance of small and medium-sized mammals in remnant urban bushland?

We took advantage of cat regulations enacted within differing subdivisions in the City of Armadale, Western Australia, to test the hypotheses that the species diversity (measured by the Shannon-Weiner index) and abundance of small and medium-sized mammals should be higher in native bushland within or adjacent to subdivisions where cats are restricted compared to similar areas where cats are not restricted. There were three different regimes of cat regulation: no-cat zone (strict prohibition of cat ownership applying in one site), compulsory belling of cats and night curfew at one site, and unregulated zones (free-roaming cats applying at two sites). Both sets of cat regulations were in place for approximately 10 years prior to our survey. We also measured structural and floristic features of the vegetation at each site that might influence the species diversity and abundance of small and medium-sized mammals independently or interactively with cat activity. No significant differences in species diversity were found across the sites and KTBA (known-to-be-alive) statistics for Brushtail Possums Trichosurus vulpecula and Southern Brown Bandicoots Isoodon obesulus, the two most abundant medium-sized mammals present, were similar across all sites. The smaller Mardo Antechinus flavipes, which could be regarded as the most susceptible to cat predation of all the native species trapped because of its size, was trapped mostly at an unregulated cat site. Total mammals trapped at the unregulated cat sites exceeded those caught at the two sites with restrictions, but these unregulated sites also had significantly denser vegetation and there was a borderline (p = 0.05) rank correlation between vegetation density and mammal captures across all sites. It appears that pet cats are not the major influence on the species diversity or abundance of small and medium-sized mammals at these sites and that vegetation characteristics may be more important.

Body temperature variation of free-ranging and captive southern brown bandicoots Isoodon obesulus (Marsupialia: Peramelidae)

To investigate patterns of thermoregulation in free-ranging and captive southern brown bandicoots Isoodon obesulus, we measured abdominal body temperature ( T b) of five free-ranging bandicoots over 42 days using implanted data loggers and T b of three captive bandicoots over 3 months using implanted temperature-sensitive radio transmitters. Bandicoots in the wild had a mean T b of 36.5±1.0 °C (range 33.4–39.8 °C) and showed a pronounced nychthemeral pattern with two distinct temperature phases. T b increased at 13:30±2.6 h each day and remained high for 10.65±2.07 h, suggesting a crepuscular and early evening activity pattern. Daily T b variation of I. obesulus would save considerable energy by reducing daytime thermoregulatory costs in the wild. Captive bandicoots had a similar mean body temperature (36.9±0.2°C) and range (33.0–39.9°C) as free-ranging bandicoots. However, the nychthemeral T b pattern of captive bandicoots was different from free-ranging bandicoots, with a less pronounced daily cycle and the nocturnal rise in T b occurring mainly at sunset and the daily decline occurring mainly at dawn.

Morphological and molecular characteristics of a species of Hepatozoon Miller, 1908 (Apicomplexa: Adeleorina) from the blood of Isoodon obesulus (Marsupialia: Peramelidae) in Western Australia

Examination of blood films as part of a study to assess the health status of the southern brown bandicoot Isoodon obesulus (Shaw) in Western Australia revealed the gamonts of a haemogregarine parasite in some samples, the first to be recognised in a bandicoot in this state. Light microscope morphological characteristics and partial sequence of the 18S rRNA gene were used to describe these organisms. Morphological characters did not differentiate the organism in the current study from previously reported Hepatozoon peramelis (Welsh & Dalyell, 1909). Phylogenetic analysis has not previously been reported for any species of Hepatozoon from Australian marsupials and consequently could not be used to confirm the identity of the organism in the current study as that described in the 1900s. If this organism is H. peramelis, then it has a wide distribution, being found in three species of bandicoot, in western and eastern Australia and the in island state of Tasmania.

Responses of four Critical Weight Range (CWR) marsupials to the odours of native and introduced predators

In Australia many critical weight range (CWR) species are threatened by predation from the introduced Red Fox Vulpes vulpes. Understanding how these prey species respond to native predators such as the Tiger Quoll Dasyurus maculatus, and comparing their responses to foxes is important in understanding why fox predation is such a problem. Many northern hemisphere mammalian species have developed responses to the odours of the main species which prey upon them. The situation in Australia remains unclear. We looked at the effect of scenting traps with the faeces of the Tiger Quoll and the Red Fox on the capture rates of four species of CWR marsupials, the Long-nosed Bandicoot Perameles nasuta, the Southern Brown Bandicoot Isoodon obesulus, the Northern Brown Bandicoot I. macrourus and the Common Brushtail Possum Trichosurus vulpecula. None of these species responded to fox odour. However despite low capture rates, Northern Brown Bandicoots and Common Brushtail Possums were captured significantly more often i...

Predation of southern brown bandicoots Isoodon obesulus by the European red fox Vulpes vulpes in south-east Victoria.

PREDATION by European red foxes (Vulpes vulpes) has been identified as at least partially responsible for local declines of populations of many small to medium-sized mammals in Australia and is listed as a ‘key threatening process’ under the Victorian Flora and Fauna Guarantee Act, 1988 and the Federal Environment Protection and Biodiversity Conservation Act, 1999. Foxes occur in large numbers throughout urban, suburban and rural areas where they opportunistically take carrion, small to medium-sized mammals, birds, insects and fruit (Menkhorst 1995; Marks and Bloomfield 1999). They also kill poultry and larger mammals such as macropod species and sheep (Menkhorst 1995). In many conservation areas, particularly in near-urban locations where fox densities are high, they are thought to pose a serious threat to biodiversity conservation (Menkhorst 1995; Friend et al. 2001; Mahon 2001).

Inheritance of geographic variation in body size, and countergradient variation in growth rates, in the southern brown bandicoot Isoodon obesulus.

The inheritance of geographic variation in body size in the southern brown bandicoot (Isoodon obesulus) was investigated through a common-environment crossbreeding experiment. The geographic variation in body size is related to habitat type, suggesting that it may be adaptive. Adults from two locations in Western Australia, Perth (large animals) and Albany (small animals), were collected and offspring from both hybrid and non-hybrid matings were reared under controlled conditions. All four variables examined (head length, pes length, ear length and body weight) were found to possess a large genetic component, supporting the interpretation that the geographic variation in size is adaptive. The three length variables initially showed additive genetic variation, although the variation in body weight displayed dominance. Genetically controlled differences in growth rate were also detected, with the smaller animals, found in the relatively poorer environment, possessing the faster intrinsic growth rate. Thus, not only does there appear to be adaptive divergence in initial body size, but the countergradient variation in growth rates provides additional evidence for adaptive divergence in this species.