Pests are often viewed as having consistently strong and negative effects on biodiversity values and agricultural productivity, especially if they have been introduced from elsewhere. However, pests do not necessarily have just negative impacts, and there is evidence that in some situations their effects can be beneficial. The positive effects of pests arise when they become deeply embedded in ecological communities and are involved in webs of direct and indirect interactions with other species. In this paper, I first outline the concepts of direct and indirect interactions, and then describe two case studies that illustrate how these interactions develop between pests and native animals. In the first case study, house mice ( Mus domesticus ) introduced to Boullanger Island in Western Australia have direct effects on a small dasyurid marsupial ( Sminthopsis griseoventer boullangerensis ), but also exert indirect negative and indirect positive effects on four species of insular skinks. In the second case study, high levels of activity of domestic house cats ( Felis catus ) in suburban bushland in Sydney are associated with reduced richness of bird species. However, high cat activity also appears to depress the rate of egg predation in above-ground bird nests, apparently by suppressing the activities of small egg predators such as rats. In these and other examples, control of the putative pest would have unintended negative consequences on some native species, making decisions about management more difficult. I propose a preliminary framework to predict the likelihood of indirect interactions occurring at different times after a pest has been introduced, at different places, and at different pest densities, and use this to suggest options for management of the pest species.

We reviewed published, quantitative studies examining the effects of exotic plants in native vegetation on the species richness and abundance of birds and mammals. We asked whether the incursion of exotic plants into native vegetation has led to consistent declines, increases or no changes in bird and mammal species richness and abundance. Bird species richness and abundance tended not to be lower in sites with exotic plants (exotic sites) compared with sites without exotic plants (native sites). However, there are some reported cases of declines in richness, and declines and increases in abundance of birds in exotic sites. While there is not enough evidence to generate broad patterns in relation to species richness of mammals in exotic sites, abundances of individual mammal species demonstrated idiosyncratic responses (either increases, decreases, or no changes) to the incursion of exotic plants. Any differences observed in species richness and abundance of birds and mammals between exotic and native sites are probably due to habitat modifications by exotic plants resulting in changes to vegetation that is important for foraging, protection, and reproduction of the vertebrates. Importantly, our review found no published, quantitative evidence that the incursion of exotic plants into native vegetation leads to the over-abundance of any bird or mammal species. Nevertheless, the results of our review must be viewed as preliminary findings: there is still much to be done to untangle the complex ecological effects of exotic plants on birds and mammals in native vegetation.

Censuses were taken of three common species of small mammals at forest sites in four regions in the Australian Capital Territory and New South Wales. Numbers of Agile Antechinus Antechinus agilis were best predicted by indices of abundance of tree hollows and invertebrate food resources, whereas numbers of Brown Antechinus Antechinus stuartii were associated most consistently with tree hollows and then numbers of logs and coexisting Bush Rats Rattus fuscipes . Rats were not associated consistently with any single habitat components, but generally favoured sites of high vegetation density with litter or logs providing ground-level cover. Rattus fuscipes was the only species to show a difference in abundance between forest types, being 2.6 times more numerous in tall open-forest than open-forest in one study area. Radio-tracking confirmed that the habitat components most strongly associated with the local abundance of A. stuartii and R. fuscipes were used as day time shelters by each species. Because the three study species are common in forest environments in eastern Australia, they are not considered important from perspectives of conservation or management. However, in local areas where common species reach high numbers, they will be more important in controlling energy, nutrient and resource flows than rare species, and are more likely to be involved in interaction webs and co-evolutionary relationships with suites of other species. The tree hollows, logs and other habitat components associated with high local abundances of our common study species are also components required by many less common and threatened species of vertebrates. In view of these observations, we suggest that ‘hot spots’ of common species may act as uniquely important indices of local resource and species richness, and thus of local forest quality. An exciting and profitable line of research would be to compare the performance of a ‘common species index’ with more traditional measures of forest quality such as presence of threatened species, species richness or structure-based indicators.

As specified by the NSW Threatened Species Conservation Act 1995 , the Scientific Committee is responsible for listing threatened species, populations, ecological communities and key threatening processes in schedules of the Act, as well as for several review and advisory tasks. In this paper, I outline the composition, structure and functioning of the NSW Scientific Committee during its first seven years of operation (1996-2002), and then describe the Committee's approach in evaluating five nominations of different entities for listing. Each generated debate about different aspects of the listing process, the amount and quality of information required for the Scientific Committee to be able to make a determination, and about how criteria for listing different entities in the Act should be interpreted. From the debates, the Committee was able to develop robust and effective protocols for review of nominations and assessment of status. These protocols allowed the Scientific Committee to process some 600 nominations for listing and delisting of species, populations, communities and key threatening processes during its first seven years of operation, and should continue to assist the Committee to function in future.

Macro- and microhabitat relationships were analysed within a lizard community from the Simpson Desert, Queensland, Australia. Three macrohabitat categories (dune crest, side and swale) and six microhabitat variables (soil hardness and five ground cover estimates) were investigated. Most captures of lizards (46%) and 25 of 36 species were found on dune crests, with four species being restricted almost exclusively to crests. Proportions of captures were less on dune sides and swales (28 and 26% respectively) than on crests, but 25 and 28 species respectively occurred in these habitats. At the microhabitat level the variables most frequently associated with abundance of different species of lizard were soil hardness and cover of spinifex Triodia basedowii . Microhabitat associations reflect selection by individuals for local sites that provide specific shelter, foraging or thermoregulation requirements, but firm conclusions are difficult to draw due to auto-correlation between microhabitat variables and limited knowledge of the autecology of most species. We conclude that differences in habitat provide an important axis for species separation among desert lizards, and that local species diversity is enhanced by dune topography.

An assemblage of frogs was monitored for 23 months in an arid sand dune habitat in southwestern Queensland. Three species were present, Notaden nichollsi, Neobatrachus centralis and Cyclorana australis. N. nichollsi was the most abundant species making up 77.0 per cent of all captures, followed by N. centralis (18.2%) and C. australis (4.8%). All three species were active on the surface only after rain and while water was present in the claypans. During periods of activity, frogs were the dominant terrestrial vertebrates in the area both in terms of numbers and biomass. Large frogs captured during rain were found near the crests of the dunes, while juveniles were captured two to three weeks after rain in the swales. The numbers of N. nichollsi captured were positively correlated with the ranked distance to the nearest claypan. All three species had markedly different diets, and the dietary composition differed from that of available invertebrates. Termites were a major component of the diet of both N. nichollsi and N. centralis, although no termites were present on the surface during the study. We suggest that frogs are an important, but largely over looked, element of the Australian desert fauna.

The importance of trees as nesting and foraging sites was investigated for 12 species of small, native, ground-dwelling mammals in 13 forests in southeastern and southwestern Australia. At least half of all observed foraging occurred on tree surfaces or hollows, loose bark, logs or leaf litter; limited observations were made of foraging on open ground or among shrubs or rocks. Most observations (86%) of above-ground foraging were in large, mature trees with complex branching systems. In forests dominated by ribbon gum Eucalyptus viminalis , the suitability of trees as foraging substrates for insectivorous mammals changed seasonally with the peeling of bark; in spring the trees harboured rich populations of invertebrates under the detaching bark, but after bark peeling in summer, invertebrates migrated to the bases of the trees or the ground. Nest and shelter sites occurred mostly in hollows in mature or senescent trees, in logs or leaf litter. These findings suggest that the requirements of several species of terrestrial mammals are best met by large, mature trees and a complex ground layer that includes logs and leaf litter. Some management recommendations are that: 1. logging cycles be extended to allow hollow formation; 2. areas with large or diverse populations of ground-dwelling species be set aside or only selectively logged; 3. control burning be minimized to allow retention of nest and foraging sites; 4. logged areas be widely separated within forests to maintain structural diversity; and 5. research be initiated to determine the long-term effects of different forestry operations on the numbers and diversity of ground-dwelling mammals.