Showing papers in "Wildlife Research in 2001"

Kullback-Leibler information as a basis for strong inference in ecological studies

Abstract: We describe an information-theoretic paradigm for analysis of ecological data, based on Kullback–Leibler information, that is an extension of likelihood theory and avoids the pitfalls of null hypothesis testing. Information-theoretic approaches emphasise a deliberate focus on the a priori science in developing a set of multiple working hypotheses or models. Simple methods then allow these hypotheses (models) to be ranked from best to worst and scaled to reflect a strength of evidence using the likelihood of each model (gi), given the data and the models in the set (i.e. L(gi | data)). In addition, a variance component due to model-selection uncertainty is included in estimates of precision. There are many cases where formal inference can be based on all the models in the a priori set and this multi-model inference represents a powerful, new approach to valid inference. Finally, we strongly recommend inferences based on a priori considerations be carefully separated from those resulting from some form of data dredging. An example is given for questions related to age- and sex-dependent rates of tag loss in elephant seals (Mirounga leonina).

A review of methods to estimate the abundance of terrestrial carnivores using field signs and observation

Abstract: This paper reviews field methods for estimating and monitoring the abundance of terrestrial carnivores that do not involve capture. Effective methods of monitoring abundance are important tools for the management and conservation of many species. The development of methods for carnivores presents particular challenges, as they are often secretive and widely dispersed. Nevertheless, a variety of approaches based on direct observations and quantification of field signs have been employed. These techniques are described in relation to carnivore ecology and resource implications, and the advantages and deficiencies of each are discussed with reference to case studies. Estindasvore G.ls J W033 Ga J. Rlah

Population dynamics, diet and aspects of the biology of feral cats and foxes in arid South Australia

Abstract: Average cat and fox densities at Roxby Downs, in northern South Australia, of 0.8 and 0.6 km–2 respectively, determined through spotlight counts over a 10-year period, probably considerably underestimate true densities. Peak rabbit populations coincided with high fox numbers, which probably suppressed cat densities. Cat abundance peaked when fox numbers were low but rabbit numbers were relatively high. When abundant, rabbits were the principal prey of both cats and foxes. Declines in rabbits numbers coincided with dramatic declines in fox numbers. By contrast, declines in cat populations were less marked, presumably because they could more effectively switch to hunting a wide range of native vertebrates. Sand-dwelling lizards, house mice and common small passerines were the most abundant non-rabbit, vertebrate prey taken by cats. We estimate that annual cat predation accounted for approximately 700 reptiles, 150 birds and 50 native mammals per square kilometre, whereas foxes consumed on average 290 reptiles per square kilometre and few native mammals and birds in the Roxby Downs region each year. Male cats and foxes were heavier than females. Feral cats typically weighed less than 4.0 kg, and cats weighing less than 2.5 kg typically preyed on more native vertebrates than did larger cats. Male and female cats were both typically tabby coloured, but a higher proportion of males were ginger in colour. Peak cat breeding coincided with rabbit and bird breeding and increased reptile activity during spring.

Population dynamics of three species of dasyurid marsupials in arid central Australia: a 10-year study

Abstract: This study investigated the population dynamics of three species of dasyurid marsupials in sand ridge habitat of the Simpson Desert, western Queensland, over a 10-year period between March 1990 and December 1999. The lesser hairy-footed dunnart (Sminthopsis youngsoni), was captured most consistently over the period of study, followed by the wongai ningaui (Ningaui ridei), and the mulgara (Dasycercus cristicauda). Rates of recapture were low (4.5–22.2%), probably because individuals of each species are very mobile. All species bred in late winter or early spring when animals were aged at least 8–10 months, and independent juveniles first appeared usually in summer. S. youngsoni reared a second litter in late spring or early summer in 3 of the 10 years studied, when the availability of food was likely to have been high; neither N. ridei nor D. cristicauda were known to attempt a second litter within a season. To explore factors that might influence population dynamics, we compared capture rates of each species with measures of rainfall, temperature, vegetation cover, abundance of predators [feral cats (Felis catus), red foxes (Vulpes vulpes), and goannas (Varanus spp.)], dragons, other dasyurids and indices of food abundance. The abundance of S. youngsoni appeared to depend primarily on the cover of spinifex 7–9 months earlier, that of D. cristicauda was related most strongly to rainfall 7–9 months earlier, while that of N. ridei was related to minimum temperature lagged by 1–3 months. While the dynamics of other arid-zone mammals are driven demonstrably by interactions between rainfall, resource availability and predation, our findings suggest that dasyurids have limited flexibility in their life histories and are influenced more subtly and by factors such as facilitation that are just beginning to become apparent.

Effects of tropical rainforest roads on small mammals: inhibition of crossing movements

Abstract: Along a narrow, unsealed road through rainforest in north-eastern Queensland, movements of small mammals were examined to determine whether the road would inhibit road crossings, thereby causing linear barrier effects. Crossings of a 12- or 20-m-wide road clearing by Melomys cervinipes were severely inhibited, crossing inhibition of Rattus sp. was less severe, while crossings by Uromys caudimaculatus were unaffected. This differential effect was attributed to species differences in size, mobility and behaviour. Baiting on only one side of the road increased crossing rates for all species. During the breeding season, crossings of 20-m clearings by Rattus sp. were almost completely inhibited and were significantly fewer than crossings of 12-m clearings. Clearing width had little effect on crossing rate outside the breeding season. Seasonal dispersal of juvenile and breeding animals appeared to explain this discrepancy in clearing-width effects. Rattus sp. were significantly less likely to cross a road where there was no vegetative cover at the entrance to a road culvert than where there was cover at both culvert entrances. Linear barrier effects for small mammals may be mitigated by narrower road-clearing widths, by replanting of grassy road verges resulting in increased cover at culvert entrances and canopy closure above the road, and by providing more faunal underpasses.

The distribution and abundance of ground-dwelling mammals in relation to time since wildfire and vegetation structure in south-eastern Australia

Abstract: Vegetation undergoes a natural succession after wildfire. Following an initial flush of vegetation, when light and other resources become limiting, the stand structure rapidly reaches a maximum. As a result, vegetation structure does not form an even distribution over the landscape, but rather a patchwork pattern. The position and characteristics of a patch of habitat in the landscape may be critical in determining the faunal composition. In this paper a sequence of ‘habitat complexity scores’ (which describe vegetation structure independently of plant species) collected over 20 years following a wildfire was utilised to estimate vegetation structure in relation to time since fire. This information was compared with data collected over the same period on medium-sized and large grounddwelling mammals to examine the response of mammals to changes in vegetation structure. Models are presented of the response of ground-dwelling mammals to time since wildfire and to changes in habitat complexity scores, with predictions up to 25 years after wildfire.

The ecology of an Australian reptile icon: how do blue-tongued lizards (Tiliqua scincoides) survive in suburbia?

Abstract: Although most species of large reptiles in the Sydney region are now restricted to remnant bushland, the blue-tongued lizard (Tiliqua scincoides) remains abundant. How has this large, slow-moving reptile managed to persist in the suburbs? We implanted radio-transmitters into 17 adult blue-tongued lizards and tracked them for six months (October 1998 to March 1999). Radio-tracked animals utilised 5–17 suburban backyards, but each lizard spent most of its time in a few ‘core’ areas near 2–7 shelter sites. Males had larger home ranges than females (mean of 12700 v. 5100 m 2 ) and moved further between shelter sites. Gravid females (mean home range 1000 m 2 ) were more sedentary. Lizards used corridors of dense vegetation to move between retreat sites, and actively avoided crossing roads. In sunny weather, lizards typically basked close to their overnight shelter for 1–4 h each morning until they obtained body temperatures of approximately 32°C. They maintained high body temperatures while moving about in the afternoon. In combination, the following ecological factors may facilitate persistence of blue-tongued lizards at our suburban study sites. (i) The most important subgroup of the population in terms of conservation are gravid females, which are highly sedentary and, thus, less likely to encounter the dangers of suburbia. (ii) The more ‘expendable’ males move about much more, but mostly in times and places that involve minimal risk from humans and their domestic pets. (iii) Lizards show strong site fidelity, spending up to 70% of their time in ‘safe’ locations; importantly, they avoid roads. (iv) Blue-tongued lizards readily utilise ‘artificial’ shelter sites and the commensal prey species (e.g. snails) found in most gardens. (v) These lizards can grow rapidly, mature early, and produce large litters. Because blue-tongued lizards have a long life span (over 30 years in captivity), populations of adults may persist for many years in the absence of recruitment.

Seasonal changes in the diet, food availability and food preference of the greater bilby (Macrotis lagotis) in south-western Queensland

Abstract: Diet and food availability of the greater bilby (Macrotis lagotis), was examined at two sites and over two summer and two winter seasons in Astrebla Downs National Park in south-western Queensland. The presence of both invertebrate and plant material in almost all faecal pellets (99.6% and 98.5%, respectively) indicated that bilbies in south-western Queensland are omnivorous. The plant component of the bilby diet consisted predominantly of Dactyloctenium radulans seeds (frequency of occurrence: 94.4%). The major invertebrate prey items were Isop-tera (termites, 73.1%) and Formicidae (ants, 77.6%). The frequency of occurrence of invertebrates in faecal pellets was higher during summer than winter, but the frequency of occurrence of plants was relatively constant regardless of season. Within the invertebrate categories, Isoptera and Acrididae (grasshoppers) displayed the greatest seasonal difference, with a significantly higher proportion of both categories in the diet during summer than winter at both study sites. The availability of invertebrate prey items also varied with season, and for most taxa, frequency of oc-currence was significantly higher in summer than winter. In contrast, the frequency of occurrence of seeds and bulbs (Cyperus bulbosus) varied only slightly with season. Seasonal changes in food availability were reflected by variation in dietary composition; however, relative proportions of some dietary items differed from their proportional availability. Therefore, bilbies were considered to be qualitatively opportunistic; selecting more invertebrates when their apparent availability increased, but continually exploiting the available seeds and bulbs. Additionally, although bilbies appeared to have some preferences for particular food items, several food items were selected almost randomly, and therefore bilbies were also considered to be dietary generalists. Such an opportunistic feeding strategy is advantageous to an arid-zone species as it permits the continuous exploitation of food resources that are unpredictable in their availability both spatially and temporally.

Seasonal use of savanna landscapes by the Gouldian finch, Erythrura gouldiae, in the Yinberrie Hills area, Northern Territory

Abstract: The diet, attributes of feeding sites and patterns of seasonal movements of a population of the Gouldian finch, Erythrura gouldiae, were studied in the Yinberrie Hills area north of Katherine in the Northern Territory. In the dry season (April–November) Gouldian finches foraged mostly on burnt ground and fed on exposed seed of annual grasses, especially seed of spear-grass, Sorghum spp. In the wet season (December–March) Gouldian finches fed on seed of a sequence of perennial grass species, including Themeda triandra, Alloteropsis semialata, Chrysopogon fallax and Heteropogon triticeus. Gouldian finches undertake regular seasonal shifts in habitat, from breeding areas in hill woodland in the dry season to adjacent lowlands throughout much of the wet season, in response to seasonal changes in food availability. There is an annual pulse in abundance of fallen seed in the early dry season that is depleted to near zero levels by germination of annual grasses early in the wet season. Thereafter, finches depend on seed from other sources, principally ripe and ripening seed of perennial grasses. Observations over three successive wet seasons suggest that Gouldian finches track seed resources provided by seeding perennial grasses over an extensive area of lowland grassy woodland adjacent to the breeding area, favouring small patches of grassy woodland for brief periods until seed fall. There were subtle differences between years in the types of resources used. Management of Gouldian finch populations will entail protection and management of the full range of grassland habitats used throughout the annual cycle, and will require predictive knowledge of the causes of patterning of seed resources and probably an ability to exert control over the timing and extent of fires in fire-prone seasonal savanna landscapes.

Review of the effects of organophosphorus and carbamate insecticides on vertebrates. Are there implications for locust management in Australia

Abstract: The Australian Plague Locust Commission uses the organophosphorus insecticide fenitrothion to control locust population increases across 2000000 km2 of eastern Australia. Although the impact of fenitrothion on non-target invertebrates has been studied, effects on vertebrates are largely unquantified. Lethal and sublethal impacts on vertebrates are a consequence of the use of organophosphorus and carbamate insecticides. Information detailing the effects of exposure on free-living animals, particularly for herpetofauna, is lacking. This paper reviews literature concerned with the impacts of organophosphorus and carbamate insecticides on terrestrial vertebrates and highlights the need for continued research into the effects of these chemicals, especially in Australia.

Diet of New Zealand sea lions (Phocarctos hookeri) at the Auckland Islands

Abstract: Scat and regurgitate samples (n = 206) from New Zealand sea lions (Phocarctos hookeri) were collected at the Auckland Islands between December 1994 and February 1997. Most (82%) samples were collected during three summer seasons while the remainder (18%) were collected during a single winter season. Thirty-three taxa were identified from 3523 prey items. The six most abundant prey species accounted for 90% of all prey items. The two most numerically abundant prey species, octopus (Enteroctopus zelandicus) and opalfish (Hemerocoetes species) made up almost 50% of total prey items. Other important prey species included lobster krill (Munida gregaria), hoki (Macruronus novaezelandiae), oblique-banded rattail (Coelorhynchus aspercephalus), and salps (Pyrosoma atlanticum). New Zealand fur seals (Arctocephalus forsteri) and seabirds were also identified in samples. New Zealand sea lions are generalist feeders utilising a wide variety of prey items, with fish comprising the most common taxa (59%) numerically and both cephalopods (21%) and crustacea (15%) forming lesser, but still important, parts of the diet. Prey taxa identified indicate that New Zealand sea lions are utilising a wide variety of benthic, demersal and pelagic species ranging from the inter-tidal zone to waters deeper than 300 m. New Zealand sea lions at the Auckland Islands target different prey species to New Zealand sea lions at other locations although they have broadly consistent prey types, with fish as the major taxa. There is only a small overlap of New Zealand sea lion prey species with commercially targeted species on the Auckland Islands Shelf in the months sampled.

Ecological correlates of folivore abundance in north Queensland rainforests

Abstract: The ecological factors controlling the distribution and abundance of the folivorous marsupials endemic to the rainforests of northern Australia are not understood. In this study, we surveyed folivore abundance at 40 sites stratified by altitude and geology in rainforests of the Atherton Tableland, north Queensland. All five species of folivore that inhabit the study area were more abundant in highland (800–1200 m) than in upland (400–800 m) forests. Allowing for the effects of altitude, four species of folivore were more abundant in forests on nutrient-rich basalts than in forests on nutrient-poor acid igneous or metamorphic rocks. The abundance of two folivore species also varied inversely with rainfall. Altitudinal variation in folivore abundance in the study area has been attributed to habitat destruction, Aboriginal hunting, the distribution of host plants and climate; however, none of these hypotheses has been tested. Variation in folivore abundance with geology is plausibly explained as a response to the nutritional quality of foliage. Foliage quality may also explain the inverse relationship between two of the folivores and rainfall. The results of this study show that only a relatively small proportion of north Queensland rainforests support abundant populations of the endemic folivorous marsupials.

A comparison of population estimates and abundance indices for house mice inhabiting beech forests in New Zealand

Abstract: Populations of house mice were sampled on nine grids in Fiordland National Park between May and November 1999, using live-capture and footprint-tracking tunnel methods Trapped mice were removed from three grids (approximately 324 ha each), and marked and released on the other six Density estimates were obtained using recapture data from the grids where mice were released (Mh (jackknife) model from program CAPTURE), and rate-of-capture data from grids where mice were removed (Mbh (removal) CAPTURE model) Density estimates were used to evaluate the performance of 4 indices of mouse abundance by contrasting R2-values of their regression on estimated mouse density Indices evaluated were: minimum number of individuals known to be alive (MNA) (total number of individual mice caught over the course of a trapping session), one-night trap catch (number of mice caught on first night of each trapping session expressed as captures per 100 trap-nights), three-night trap catch (same index estimated from number of mice caught over the first three nights), and tracking-tunnel index (proportion of nine tunnels that had mouse tracks) While MNA, one-night trap catch, and three-night trap catch were all significantly correlated with estimated density, MNA was most strongly correlated, with R2 varying between 067 to 087 depending on whether 3, 4 or 5 nights’ capture data were used Variation in tracking-tunnel index was unrelated to mouse density on our grids

Dietary overlap between the burrowing bettong (Bettongia lesueur) and the European rabbit (Oryctolagus cuniculus) in semi-arid coastal Western Australia

Abstract: The diets of burrowing bettongs and European rabbits were studied on Heirisson Prong at Shark Bay, Western Australia, over two winters (1996 and 1997) and two summers (1996/97 and 1997/98). This was during a period when the rabbit population was increasing to high levels and projected foliage cover was decreasing, presenting environmental conditions likely to exacerbate competition. The diets of bettongs and rabbits were significantly different in both winter and summer. The mean overlap in diets shifted from 43% in winter to 56% in summer. Bettongs were able to vary their diet in response to environmental conditions while rabbits perished in large numbers during the second summer. The winter diet of bettongs included hypogeal fungi (19-23%), fruit and forbs; their summer diet included seed, stem, and the foliage of shrubs. Grasses dominated the winter diet of rabbits; forbs, 'other shrub species', and browse from shrubs were included also. In summer, rabbits ate mainly roots (30-35%), browse and stems from shrub species. Bettongs ate food items that rabbits did not, and were better able to use common resources. The lack of significant dietary overlap between rabbits and bettongs suggests minimal competition at times of potentially limited food resources. These results suggest that rabbits alone are unlikely to have brought about the mainland extinction of bettongs.

The effect of habitat type and seasonal conditions on fauna in two areas of the Tanami Desert

Abstract: Australian deserts are characterised by highly patterned plant productivity and an extremely unpredictable climate. The Tanami Desert in central Australia is dominated by vast sandplains interspersed with more productive habitats such as palaeodrainage lines. During 1996 and 1997 fauna surveys were conducted in two areas of the Tanami Desert to investigate the relative importance of palaeodrainage habitat for fauna under different seasonal conditions. The two areas were at latitudes separated by approximately 400 km, and during the study period the northern study area (Tennant) received considerably more rainfall than the southern study area (Kintore). The species richness and abundance of a range of taxonomic groups were compared between the two study areas and between palaeodrainage habitat and adjacent sandplain habitat. The only significant difference between habitats was that small reptiles were more abundant in sandplain than palaeodrainage habitat. Overall, bilbies, bustards and macropods were significantly more abundant at Tennant than Kintore, but significantly more small mammals were captured at Kintore. In both habitats and areas, capture rates, track counts and species richness of reptiles varied significantly with season. The biomass of invertebrates captured also showed significant temporal fluctuations. Burrowing frogs were active only after rain, and birds showed significant fluctuations in abundance and species richness associated with rainfall. The abundance of small mammals did not vary significantly during this study. Overall, local seasonal conditions were generally more important determinants of the abundance of fauna in the spinifex grasslands of central Australia than was habitat type.

Stability of nest range, home range and movement of the northern bettong (Bettongia tropica) following moderate-intensity fire in a tropical woodland, north-eastern Queensland

Abstract: Nest use, home-range characteristics and nightly movements by the northern bettong (Bettongia tropica) were examined before and after a low- to moderate-intensity fire in sclerophyll woodland in north-eastern Australia using radio-telemetry. In all, 23 animals were radio-tracked at three-month intervals between February 1995 and May 1996. During November 1995 a low-intensity experimental fire burned the entire home range of most animals. The northern bettong appeared fairly catholic in choice of nest site, with a variety of nest locations and nesting materials used. Prior to the fire, nests were generally located in areas of dense cover, such as the skirts of grass trees (46%) or grass close to a log (29%). After fire removed most ground cover in the nesting areas of most animals, bettongs used remaining shelter such as boulder piles (45%), recently fallen trees (8%) and patches of unburnt vegetation (21%). Nest areas (10.1 ha) of males were significantly larger than those of females (5.4 ha). Home ranges of both sexes were large (59 ha) and most ranges lacked distinct core areas, suggesting that bettongs used all parts of their home ranges equally. High mean rates of nightly movement by the northern bettong indicated that large distances were moved within home ranges during nightly foraging. No significant fire-related changes were detected in home-range size, home-range location, nest-area location or mean rates of nightly movement, suggesting that the northern bettong is well adapted to the low- and medium-intensity fires that characterise its habitat.

Home-range use by the brush-tailed phascogale (Phascogale tapoatafa) (Marsupialia) in high-quality, spatially limited habitat

Abstract: Nine phascogales (7 females, 2 males) were radio-tracked between March and July 1999 to investigate the spatial organisation of this species in spatially limited habitat near Euroa, Victoria. In this area, approximately 3.6% of the original woodland vegetation remains after 150 years of agricultural clearing. Most wooded habitat is confined to narrow linear strips along roads and streams. However, these remnants are on fertile soils and, because they have not experienced intensive harvesting, the density of large old trees is over 10 times that found in nearby State Forests and Parks. Female phascogales were monitored for 13–38 days over periods of 5–15 weeks. The size of home ranges of females was 2.3–8.0 ha, and averaged 5.0 ha. This value is one-eighth the mean home-range size previously recorded for the species in contiguous forest in Victoria. All individuals used multiple nest trees, with nests generally located in trees >80 cm diameter at breast height. Although fragmented and spatially limited, the stands of large old trees on productive soils near Euroa provide a network of well connected, high-quality habitat for phascogales. The relatively dense population of phascogales in these remnants suggests that prior to agricultural clearing and timber harvesting, phascogales may have been much more common in Victoria than at present.

Effects of fragmented habitat and fire on the distribution and ecology of the swamp antechinus (Antechinus minimus maritimus) in the eastern Otways, Victoria

Abstract: This study investigated the distribution, habitat and population dynamics of the swamp antechinus (Antechinus minimus maritimus) in the eastern Otway Ranges. The species has a restricted, disjunct distribution and has been recorded at 25 sites between 1969 and 1999. All sites were located within 7 km of the coast, occurred at altitudes up to 80 m above sea level and within 10 m of a gully. Analysis of landscape site variables identified sun index as being significant in determination of the probability of occurrence of A. minimus. The presence of A. minimus is negatively associated with sun index, occuring at sites that have a southerly aspect and gentle slope. A. minimus was located in a range of structural vegetation including Open Forest, Low Woodland, Shrubland and Hummock Grassland and a number of floristic groups, some characterised by high frequencies of sclerophyll shrubs, others by high frequencies of Pteridium esculentum, hummock grasses and herbaceous species. A. minimus occurs in fragmented, small populations with maximum population densities of 1.1–18 ha–1. Populations at inland sites became extinct after the 1983 wildfire which burnt 41 000 ha. These sites have not been recolonised since, while on the coast the species did not re-establish until 1993–97. One population that is restricted to a narrow coastal strip of habitat is characterised by high levels of transient animals. The species is subject to extinction in the region due to habitat fragmentation, coastal developments and fire. Management actions to secure the present populations and ensure long-term survival of the species in the area are required and include implementation of appropriate fire regimes, prevention of habitat fragmentation, revegetation of habitat, and establishment of corridor habitat.

An assessment of the accuracy and reliability of hair identification of south-east Australian mammals

Abstract: The aim of this experiment was to quantify the accuracy and reliability of identifying mammals from hair samples, using two highly skilled practitioners. Hair samples were collected from 37 mammal species occurring in south-eastern Australia. This material was divided into 252 samples, which were then used in a blind test to determine the accuracy of the technique. The taxa were then grouped into reliability categories based on the accuracy and consistency of the practitioner’s identifications. In all, 23 taxa, including 19 species, were regarded as being reliably identified from hair analysis. Identification of the remaining 18 species involved at least some level of error. Several factors influenced the accuracy of identifications in this study, principally (1) the need to identify samples to species level wherever possible, rather than not making an identification, and (2) the diverse range of species used (from across Victoria) and the lack of collection locality. Target species have been grouped into reliability categories, as a guide to aid evaluation of field-derived data. We emphasise the need for practitioners to gain considerable personal experience of the technique, the diagnostic characteristics used to identify hair of different species and intra-specific variation, in order to maximise the reliability of identification results.

Pythons in the pergola: the ecology of 'nuisance' carpet pythons (Morelia spilota) from suburban habitats in south-eastern Queensland

Abstract: Carpet pythons (Morelia spilota) are large (to >4 m, 11 kg) non-venomous snakes that are widely distributed across mainland Australia. In many parts of their range, viable populations persist even in highly disturbed urban and suburban habitats. Over a six-year period, we collected 258 'nuisance' pythons from two cities (Brisbane and Ipswich) in south-eastern Queensland. Most of these snakes were reported by members of the general public, often after the snakes had consumed domestic pets or cage-birds. We provide data on seasonal activity patterns, body sizes, sexual size dimorphism, reproduction and food habits of these snakes. Snakes were active and fed year-round, primarily on domestic and commensal birds and mammals. Dietary composition shifted with body size: one small snake consumed a lizard, intermediate-sized snakes took mostly mice, rats and parrots, and large snakes fed on larger items such as cats, brushtail possums and poultry. Adult male pythons engaged in combat bouts during the breeding season, and (perhaps as an adaptation to enhance success in such bouts) grew larger and were more heavy-bodied than conspecific females.

Trapping and demographics of feral cats (Felis catus) in central New South Wales

Abstract: A total of 76 feral cats (Felis catus) (29 individuals; 47 recaptures) was trapped during 6027 trap-nights using both cage and leg-hold traps from November 1994 to August 1996 at Lake Burrendong in central New South Wales. No significant difference was found in the relative capture efficiency between cage and leg-hold traps (P > 0.05). Overall capture efficiency was 1.3 cats per 100 trap-nights, although this varied seasonally, being higher in late autumn and early winter. Most cats were caught with rabbit as bait, and visual and olfactory lures added to baits did not appear to increase capture efficiency, although the power of the test was limited. Most captured cats were adult males weighing 4.37 0.14 kg; these were larger than the females (3.34 0.06 kg). Litters, comprising 2–5 kittens, were born between September and March.

Diet of a large carnivorous lizard, Varanus varius

Abstract: The diet of a population of lace monitors, Varanus varius, at Lake Burrendong was examined over the spring, summer and autumn seasons. Carrion dominated the diet; it was eaten consistently in all seasons by all the monitors and was generally supplemented by live mammalian kills and invertebrates. Nestling birds and rabbits as well as bird and reptile eggs were eaten mainly during the flush periods of the spring and early summer. The data reported here agree with other reports for the genus Varanus: that they are generalist carnivorous predators and scavengers.

Edge effects on the distribution and abundance of birds in a southern Victorian forest

Abstract: An important consequence of habitat fragmentation for wildlife communities is the effect of an increase in the ratio of habitat edge to interior. This study compares the bird communities at forest/farmland edges and in forest interior at Bunyip State Park, Victoria. Overall, there was a significantly higher number of bird species and individuals in forest edge than in forest interior sites. The greater diversity of species at edge sites appeared to be due to an increase in forest-edge specialists, as opposed to an influx of open-country species. Four bird species: the white-throated treecreeper (Cormobates leucophaeus), the superb fairy-wren (Malurus cyaneus), the grey shrike-thrush (Colluricincla harmonica) and the grey fantail (Rhipidura fuliginosa) were significantly more abundant in edge sites. There were no species that were significantly more abundant in interior sites. Differences between the bird communities in edge and interior sites were attributed to increased foraging opportunities in the open country adjacent to forest edges.

Factors affecting pitfall capture rates of small ground vertebrates in arid South Australia. II. Optimum pitfall trapping effort

Abstract: Pitfall trapping is widely used for sampling small terrestrial vertebrates. This study investigated the influence of trapping period, number of trap sites and drift fences on the capture rates of small vertebrates in order to ascertain optimum pitfall trapping efficiency. Capture rates at fenced pits were five times higher than at unfenced pits. Our study indicates that one fenced site established in chenopod shrubland in the Olympic Dam region and trapped for four nights yielded less than one third of the local chenopod shrubland reptile inventory. Capture rates of reptiles at Olympic Dam in arid South Australia were significantly higher on the first three nights of trapping than on the seven subsequent nights. The most efficient number of trap nights for maximising the number of reptile species captured was five nights. Trapping only a single pitfall site per habitat type for 5 nights captured approximately 30% of the reptile species in that habitat compared with 55%, 65% and 73% for three, five and ten sites respectively. Typically, approximately 70% of the reptile species in chenopod shrubland were captured by trapping 5 sites for 7 nights, a method recommended for thorough surveys of species present in chenopod shrublands. Captures of mammals were more variable than those of reptiles and, as a result, sampling of mammal species benefited from more trapping nights than did sampling of reptiles. New mammal species continued to be recorded at a high rate for 8 nights and even 10 sites trapped for 10 nights typically yielded only 60–80% of the species present in chenopod shrubland. Standard 4-night trapping periods adopted by most surveys will fail to detect many rare species, or those that are difficult to trap. Repeated 7-night trapping sessions for up to 21 nights are recommended for surveys where more accurate species inventories are required.

Factors affecting pitfall capture rates of small ground vertebrates in arid South Australia. I. The influence of weather and moon phase on capture rates of reptiles

Abstract: The effect of temperature, humidity, cloud cover, wind and rainfall on capture rates of small reptiles in pitfall traps was assessed in the South Australian arid zone. Capture rates increased significantly with increased ambient temperature. Captures of diurnal reptiles were highest when the minimum temperature was greater than 26°C, while captures of nocturnal reptiles peaked when maximum temperatures exceeded 34°C. Dark nights, particularly those with cloud cover, yielded higher captures of nocturnal reptiles than moonlit or cloudless nights. Representative sampling periods to record a wide range of reptile species should extend for at least 8 days, which is the modal period of a major change in daily temperature during the summer months.

Breeding biology, reproductive success and survival of blue-breasted fairy-wrens in fragmented habitat in the Western Australian wheatbelt

Abstract: We studied blue-breasted fairy-wrens, Malurus pulcherrimus, over a 6-year period in 17 differently sized remnants in a highly fragmented agricultural landscape at Wyalkatchem, Western Australia. The wrens lived in groups of 2–5 adults, comprising one breeding female, her consort and up to three helpers (usually adult male offspring). Groups lived in permanent year-round territories averaging 2.2 ha. Data from 536 nests indicated that breeding extends from August to December in good seasons but from August to October in years of drought. Overall, the average clutch size was 2.91 (median 3), although in the driest year of the study it was 2.31 (median 2). Individual nest success was low, with a mean of 1.02 fledglings produced per clutch. However, the wrens made 1.87 nesting attempts per year, thereby raising the annual reproductive output to 1.63 fledglings per group and 0.49 potential breeders per group. There was a positive relationship between nest predation and remnant size and no difference in the predation rate of nests in the largest remnant depending on how far they were located from the edge of the remnant. Nest parasitism by Horsfield"s bronze-cuckoo, Chrysococcyx basalis, was also positively related to remnant size. Consequently, annual reproductive success was higher in the 13 small remnants (2.16 fledglings per group per year), compared with 3 medium-sized remnants (1.94) and the largest remnant (1.32). Annual adult survival was 63.9% for breeding females and 67.2% for senior males. Survival was positively related to remnant size for adults, but not for fledglings. The annual survival of adults in small remnants was 54.5%, compared with 64.9% in medium-sized remnants and 68.6% in the largest remnant. It is suggested that, in order to conserve sedentary species living in fragmented habitats, we should try to retain the whole range of patch sizes that remain, even if some (or most) of the vegetation mosaic has been removed and even if some remnants are extremely small.

A simple model for ferret population dynamics and control in semi-arid New Zealand habitats

Abstract: Introduced ferrets (Mustela furo) in New Zealand are subject to population control to reduce their threat to native fauna and the incidence of bovine tuberculosis (Tb) in livestock. To help in evaluating control options and to contribute to a multi-species model for Tb dynamics, a simple Ricker model was developed for ferret population dynamics in a semi-arid environment. The model was based on two data sets and suggested an intrinsic rate of increase for ferrets of 1.0–1.3 year–1 and a carrying capacity of 0.5–2.9 km–2. There was evidence for direct density-dependence in both data sets and the effect appeared to act mainly on recruitment. Dependence of the rate of increase of predators on the density of wild rabbits (Oryctolagus cuniculus) was exhibited in one of the two data sets, together with a numerical response relating current density of predators asymptotically to current density of rabbits, their primary prey. Predators in this data set included both cats and ferrets, estimated from spotlight counts, but the other data set demonstrated a direct proportionality between predator (cat and ferret) spotlight counts and minimum ferrets known to be alive by trapping. The model suggested, firstly, that populations are hard to suppress by continuous culling, with at least a 50% removal per year necessary to effect a suppression of 50% in long-term average density. Secondly, if control is episodic rather than continuous, culling in autumn gives a greater degree of suppression over time (280%, accumulated over time) than culling in spring (180%). A differential equation version of the model provides a component for a general Anderson/May bovine Tb/wildlife (possum/deer/ferret) model.

An evaluation of two indices of red fox (Vulpes vulpes) abundance in an arid environment

Abstract: The suitability of spotlight counts to index red fox abundance was assessed in an arid environment through a comparison with a scat deposition index (active attractant). In most cases there was a high degree of correlation between the two indices, suggesting that the spotlight counts were accurately documenting fluctuations in population size. However, the precision of the spotlight index was often low (c.v. = 0.07-0.46), suggesting that the technique may not allow the statistical detection of small changes in abundance. During periods when there was an influx of new individuals into the population, the seasonal scat index displayed a three-month time lag in documenting abundance while foxes accustomed themselves to the presence of the regular food supply. The level of precision of the scat index was also found to be relatively low (c.v. = 0.21-0.48). Nevertheless, further refinements of this technique may produce a suitable measure of fox abundance.

An intraspecific and interspecific comparison of raptor diets in the south-west of the Northern Territory, Australia

Abstract: Dietary information, collected during 1995–97 in the south-west of the Northern Territory, is presented for 11 raptor species Unlike better-studied populations of these species in south-eastern and eastern Australia, most of the raptors in the arid inland were found to depend heavily on reptiles and birds, the budgerigar (Melopsittacus undulatus) being a particularly important food for many species during those periods when it was plentiful Between-territory, between-year and seasonal differences in diet are quantified for most species The raptor assemblages in central Australia included specialists on medium-sized to large mammals, small to medium-sized birds, and small reptiles/invertebrates, as well as several generalists Indices of prey diversity and evenness were calculated for each species, and diet overlap between them was used to investigate aspects of interspecific competition for food Overall, diet overlap was greatest among the bird specialists and between some of the generalists It increased in 1997, a year of comparative plenty, possibly because several species exploited an abundance of some prey taxa and competitive pressure eased

Bait palatability influences the caching behaviour of the red fox (Vulpes vulpes)

Abstract: In a free-choice experiment conducted in a series of pen trials, the influence of food preference on caching behaviour by the red fox (Vulpes vulpes) was investigated for three unpoisoned bait types: deep-fried beef liver (DFL), dried deep-fried beef liver (DDFL) and a commercial bait (Foxoff®). Although some variation in individual preferences for the DDFL and Foxoff was observed, all of the foxes in the pen trials preferred the DFL (P 0.05) and, despite some variation between the sites, DFL was the most often eaten (P < 0.001) and Foxoff the most often cached (P < 0.001). These data strongly suggest that a highly palatable bait will increase the likelihood of rapid consumption of baits and reduce the incidence of caching. This is likely to increase the cost-effectiveness of baiting and limit the potential for nontarget impacts due to the movement of baits. The high degree of concordance between the results of the pen and field trials suggests that pen trials can assist in the development of more effective bait types. However, conclusions about the relative efficacy of bait types drawn from the results of baiting programs that measure only bait uptake are unlikely to be reliable.