Environmental relationships of the brush‐tailed rabbit‐rat, Conilurus penicillatus, and other small mammals on the Tiwi Islands, northern Australia

Abstract

Aim To describe the habitat characteristics and status of the brush-tailed rabbitrat, Conilurus penicillatus Gould, 1842, on the Tiwi Islands, northern Australia, as part of a broader programme aimed at the conservation management of this species. In addition, comparable environmental modelling is undertaken for other co-occurring small native mammals, including the black-footed tree-rat, Mesembriomys gouldii Gray, 1843, a taxonomically and ecologically related species. These objectives relate to the significance for mammal conservation of islands generally in Australia, and the recent intensification of plantation forestry on these previously little-disturbed islands.Location Melville and Bathurst islands (Tiwi Islands), respectively, Australia's second and fifth largest islands.Methods A systematic survey was conducted for mammals across Bathurst (115 sampled quadrats) and Melville Island (236 quadrats). A broad range of environmental variables was recorded for every quadrat. All quadrats were classified by their woody plant species composition. The relative occurrence of individual mammal species across the resulting vegetation groups was examined using Kruskal-Wallis anova. The habitat relationships of C. penicillatus and the most commonly recorded mammal species were described by generalized linear modelling, with separate models for each island, for both islands combined, for all habitats and for only those sites dominated by eucalypts.Results Twelve small mammal species (excluding bats, macropods and feral animals) were recorded in this study. The most notable feature of this survey was the lack of records of M. gouldii from Bathurst Island. In contrast, the proportion of quadrats with C. penicillatus was not significantly different between the two islands. There was no significant tendency for these two species to co-occur in quadrats on Melville Island more or less commonly than by chance. Conilurus penicillatus was most abundant in eucalypt forest while M. gouldii showed a weak association with eucalypt forests and woodlands and shrub land. The five most commonly recorded species showed highly idiosyncratic relationships with environmental variables, with this relationship showing some variation between the two islands. None showed any significant association with floristic variation within the extensive eucalypt forests, but most showed significant associations with tree height, basal area (especially of large trees), landscape position (distance to watercourse) and fire history.Main conclusions Conilurus penicillatus was most likely to occur in tall eucalypt forest away from watercourses. This habitat is now being targeted for clearance for the development of plantations of the exotic Acacia mangium. Seven of the 12 mammal species examined in this study (C. penicillatus, M. gouldii, Rattus tunneyi

Top‐down control of species distributions: feral cats driving the regional extinction of a threatened rodent in northern Australia

“…Species distribution modelling by Firth et al . () led to the suggestion that the persistence and ‘unusually high abundance’ of C. penicillatus on the Tiwi Islands may be related to more benign fire regimes. Frequent and/or intense fires reduce the survival of C. penicillatus and pose a significant threat to the long‐term persistence of this species (Firth et al ., ).…”

“…In 2015, small mammal surveys were conducted at 88 sites in savanna forest across Melville Island (Fig. ), 86 of which had previously been surveyed in 2000–2002 (see Firth et al ., ). The 2000–2002 surveys followed the now standardized protocol for live trapping in northern Australia, which involved a 50 m× 50 m quadrat with 20 Elliot traps (33 cm × 10 cm × 9 cm) spaced equidistantly around the perimeter and four cage traps (56 cm × 20 cm × 20 cm) located on each corner.…”

Priorities in policy and management when existing biodiversity stressors interact with climate-change

“…There are already many examples of revegetation using exotic species which now pose an invasive threat (e.g. Costa et al 2004;Firth et al 2006;Harwood et al 1997;Kotiluoto et al 2009;Ren et al 2009), and there are further examples of plans to spread exotic species in an attempt to sequester carbon (e.g. Velez and Del Valle 2007).…”

Interactions among threats affect conservation management outcomes: Livestock grazing removes the benefits of fire management for small mammals in Australian tropical savannas

“…If fire recurs frequently, key food plants are disadvantaged, F I G U R E 2 Mammal species richness with changes in prevalence of late fires at the large scale. The abundance of shelter sites such as hollow logs and tree hollows are also reduced by high intensity fire, especially if these fires recur frequently (Firth, Woinarski, Brennan, & Hempel, 2006;Williams, Cook, Gill, & Moore, 1999;Woolley, Murphy, Radford, Westaway, & Woinarski, 2018). Graphical summaries of data (regression and 95% confidence band) for the top-ranked model for stocked and destocked sites F I G U R E 3 Mammal abundance with changes in fire prevalence, stocking status and habitat.…”