Showing papers in "Wildlife Research in 1999"
TL;DR: It is concluded that long-term studies should play an important role in describing temporal changes in rodent populations in arid Australia and, with field experiments, in evaluating how rainfall and other factors combine to effect the changes.
Abstract: Populations of rodents were studied for periods of 7−9 years at each of three sites in arid Australia. All species fluctuated dramatically in abundance, being absent or in low numbers during droughts but erupting after significant rainfall. Strong correlations were obtained between capture rates and cumulative monthly rainfall residuals, with time lags, that had been modified by an exponential decay function to model the post-rain depletion of resources. The introduced Mus domesticus erupted within only two months of exceptional rainfall at one site, whereas the native rodents Notomys alexis, Pseudomys hermannsburgensis and P. desertor generally responded 3Œ10 months after rain. The faster response of M. domesticus reflects its high reproductive potential compared with the native rodents, and perhaps greater immigration. Differences in magnitudes and delays in response to rainfall among the native species were due probably to differences in initial population sizes and times available for response and, for P. desertor, to between-site differences in the quality or quantity of food resources. Population declines in all species during dry periods probably followed resource shortages. Despite the usually strong linkage between rainfall and population dynamics, rain failed to trigger population responses in rodents for prolonged periods at two of the sites, and was not clearly associated with an eruption of P. hermannsburgensis at the third. The lack of a population response at one site was attributed to predation, but events at the other two remain unexplained. We conclude that long-term studies should play an important role in describing temporal changes in rodent populations in arid Australia and, with field experiments, in evaluating how rainfall and other factors combine to effect the changes.
209 citations
TL;DR: Experimental manipulations of resources, competitive interactions and predation rates are proposed as the best way to clarify which factors are most influential upon individuals, populations and communities in the post-fire environment.
Abstract: Possible impacts and mechanisms of response by Australian rodents to fire are identified and discussed in relation to the literature. Although there is considerable information on patterns of population response, there is little concerning the effect of fire on individual behaviour, mortality, or interactions at the community level. The evidence that links observed responses of rodents to habitat variables is largely correlative, and theories on mechanisms of recovery are often simplified or speculative. Experimental manipulations of resources, competitive interactions and predation rates are proposed as the best way to clarify which factors are most influential upon individuals, populations and communities in the post-fire environment.
154 citations
TL;DR: The diet of feral cats was studied at Lake Burrendong from July 1994 to June 1997; however, invertebrates contributed less and possums more to the diet in winter and summer respectively, and a significant dietary response was found to changes in rabbit abundance, but not for the other prey types.
Abstract: The diet of feral cats (Felis catus) was studied at Lake Burrendong, central-eastern New South Wales, from July 1994 to June 1997. Mammals were the major prey in 499 scats that were analysed. Rabbits (Oryctolagus cuniculus) were the staple prey, while carrion was an important secondary food. Invertebrates, other mammalian prey, vegetation, birds and reptiles were generally minor components of the diet. Few significant seasonal differences in diet were found; however, invertebrates contributed less and possums more to the diet in winter and summer respectively. A significant dietary response was found to changes in rabbit abundance, but not for the other prey types. Cats continued to prey heavily on rabbits even after a 90% decline in rabbit abundance occurred, which coincided with the advent of Rabbit Calicivirus Disease (RCD). House mice (Mus domesticus) increased in importance in the diet ten months post-RCD. Although the abundance of cats was correlated with the abundance of some prey species, other factors may have influenced the observed patterns; these are discussed.
137 citations
TL;DR: It is predicted that cats are more likely to have an impact on small vertebrates at this site and that the control of cats could lead to recoveries in the populations of native rodents, birds and reptiles.
Abstract: The diets of cats (Felis catus) and foxes (Vulpes vulpes) killed during predator control at a semi-arid site in Western Australia were studied to see which prey species may be affected by predation from these introduced predators. The number of items, biomass and frequency of occurrence of each food type in the gut contents from 109 fetal cats, 62 semi-feral cats and 47 foxes were used to calculate an Index of Relative Importance for each food category for each predator. Mammals were the most important prey group for all three predators, with rabbit being the most highly ranked prey species. The diets of feral and semi-feral cats were similar in dietary diversity but differed in the frequency of occurrence of some food categories. Native rodents, birds and reptiles occurred more frequently and were ranked higher in the diet of feral cats, and food scraps occurred more frequently in the diet of semi-feral cats. The diet of foxes was less diverse than that of either group of cats. Invertebrates and sheep carrion were more important prey categories for foxes than for cats. In the summer-autumn period, foxes ate more sheep carrion and invertebrates than they did in winter-spring. The diet of feral cats was more diverse in summer-autumn, including a greater range of invertebrates and more rodents, birds and reptiles than in the winter-spring period. We predict that cats are more likely to have an impact on small vertebrates at this site and that the control of cats could lead to recoveries in the populations of native rodents, birds and reptiles. By contrast, the control of foxes alone may lead to a rise in cat numbers and a consequent detrimental impact on small vertebrate populations.
124 citations
TL;DR: In this article, the Eudyptula minor was radio-tracked at sea during incubation, chick-rearing and non-breeding periods from 1991 to 1993.
Abstract: Little penguins, Eudyptula minor, from a breeding colony on Phillip Island, Victoria were radio-tracked at sea during incubation, chick-rearing and non-breeding periods from 1991 to 1993. Their locations, which we have assumed to reflect foraging movements, varied according to season and breeding activities, and there were marked differences from year to year. Duration and distance of trips ranged from single day-trips a few kilometres from Phillip Island, typically during the breeding season, to longer trips outside the breeding season up to 500 km away lasting more than a month, but 95% of all birds located were within 20 km of the coast. In the breeding season foraging trips averaged 4.4 days during incubation compared with 2.1 days when there were chicks in the nest; in the non-breeding period foraging trips took 5.2 days on average. The duration of trips for adults feeding chicks increased with the age of the chicks. Birds from nests on the north and south sides of Phillip Island differed in their use of areas close to the island, but showed a similar distribution on more distant trips. The location of foraging trips is discussed in relation to information on the abundance of prey species of fish within the foraging range of the birds.
96 citations
TL;DR: In this article, radio-telemetry was used to investigate roosting and movement patterns of the black flying fox (Pteropus alecto) in the seasonal tropics of the Northern Territory.
Abstract: Radio-telemetry was used to investigate roosting and movement patterns of the black flying fox (Pteropus alecto) in the seasonal tropics of the Northern Territory. Sixteen P. alecto were tracked during a 12-month period to 34 roosts and were recorded at 49 foraging sites. Pteropus alecto moved roosts seasonally, from bamboo and mangrove habitats in the dry season to rainforest in the wet season. All radio-collared male and female P. alecto roosted in rainforest during the major part of the wet season. Climatic influences may be responsible for this behaviour, with rainforest perhaps providing stable temperatures and shelter from the monsoonal rains. There was a significant seasonal difference in the distances moved by females between successive roosts. There was an association between roosting and foraging habitat: P. alecto roosting in bamboo and mangroves foraged predominantly in woodland, P. alecto roosting in rainforest foraged in Melaleucaspp. and rainforest habitat. Females covered greater distances from roosts to foraging locations than did males. Distances from roosts to foraging sites were reduced for males and females during the build- up season (September to November) and wet season (December to April). Seasonally, foraging habitat shifted both floristically and spatially with no significant difference between the sexes. The movements of one female P. alecto were recorded at hourly intervals over three consecutive nights at the beginning of the wet season. Movement patterns were very similar between nights and over these three nights she foraged in at least 7 distinct locations. The total distance moved per night was 15.5–19.9 km, including return distance to the roost, assuming straight-line movements between hourly fixes. Most foraging was done less than 6 km from the roost. The ratio of total distance moved in a night to the mean distance of forage sites from roosts was similar between nights (3.1–4.3), suggesting that a single roost site to forage site distance recorded during this study can provide an index of total foraging distance. Land tenure status identified for foraging and roosting positions recorded for P. alecto emphasises the lack of protection for habitats used by this species. Only 3% of foraging or roosting positions were recorded in any type of conservation reserve.
96 citations
TL;DR: Although remarkably adaptable in its reproductive and dietary strategies, this population of long-nosed bandicoots is likely to follow other urban bandicoot populations toward extinction unless there is active management to reduce the high rate of mortality from motor vehicles and introduced predators.
Abstract: The population biology, habitat utilisation and diet of a small, isolated population of long-nosed bandicoots (Perameles nasuta) was studied over a 22-month period at North Head in Sydney Harbour National Park, New South Wales. Reproductive output in this urban environment was high, with a mean litter size of 2.3 and production of up to four litters per year. The peak of reproductive activity was in late spring and early summer, with a cessation of breeding in late autumn or early winter. The main causes of death were identified as road trauma (58% – probably an overestimate because of the ease of finding road deaths) and predation by cats and foxes (37% – probably an underestimate because of the difficulty of locating carcasses unless radio-collared). Bandicoots utilised all macrohabitats (open grassed areas, heath, forest, swamp and scrub), but extensively used open grassed areas for foraging. Males had larger home ranges (4.4 ± 0.8 ha) than females (1.7 ± 0.2 ha). The largest home ranges of males coincided with the peak of the breeding season (September–November). Throughout the year P. nasuta fed primarily on beetles, invertebrate larvae and ants, but also on other invertebrates and on plant and fungal material. Some vertebrate and human- derived material (birdseed, vegetable scraps, plastic, twine) was also eaten. Although remarkably adaptable in its reproductive and dietary strategies, this population of long-nosed bandicoots is likely to follow other urban bandicoot populations toward extinction unless there is active management to reduce the high rate of mortality from motor vehicles and introduced predators.
77 citations
TL;DR: Ten free-roaming domestic dogs from an Aboriginal community were radio-collared to determine the sizes of their home ranges and to observe their wandering behaviour, which was highly variable within the study group.
Abstract: In this study 10 free-roaming domestic dogs from an Aboriginal community were radio-collared to determine the sizes of their home ranges and to observe their wandering behaviour. Half of the radio-tagged dogs went on wandering forays, while the other five roamed only within the vicinity of the community. Home-range size was highly variable within the study group: the mean for the wandering dogs was 927 ha whereas that of the sedentary dogs was 2.6 ha. Dogs travelled 8–30 km on forays. All forays were initiated at night and those that were recorded had an average duration of 26 h. Foray destinations were usually riparian habitats where macropod quarry were abundant.
77 citations
TL;DR: The abundance of the New Zealand sea lion, Phocarctos hookeri, was estimated using a model that incorporated estimated pup production and is among the smallest reported for a species within the Otariidae.
Abstract: The abundance of the New Zealand sea lion, Phocarctos hookeri, was estimated using a model that incorporated estimated pup production. Pups are born at only five sites, four of which are at the sub-Antarctic Auckland Islands, which lie to the south of New Zealand. The remaining breeding site is at Campbell Island in the same region. Pup production was estimated during the 1994/95 and 1995/96 breeding seasons from marknrecapture studies at the two largest sea lion rookeries, at the Auckland Islands (Sandy Bay and Dundas Island), which account for almost 90% of total pup production for the species. Pup production for the other sites was estimated from direct counts or, in the case of Campbell Island, from recent tagging data. Total pup production estimates for all sites during the 1994/95 and 1995/96 breeding seasons are 2640 and 2807 respectively. During the four-week pupping season, pup mortality at most sites was estimated to be about 10%. The estimates of absolute abundance based on pup production for the two breeding seasons were 11 700 (95% confidence interval (CI): 10 500n13 100) and 12 500 (95% CI: 11 100n14 000) respectively. This population abundance is among the smallest reported for a species within the Otariidae. The highly localised, and historically reduced distribution make this species vulnerable to impact and warrants particular attention from conservation managers. In particular, the potential impact of the annual bycatch of P. hookeri in a trawl fishery requires close monitoring and, ideally, some mitigation action.
76 citations
TL;DR: A study of confined populations of wild mice in which 67% of females were surgically sterilised to simulate the possible effects of fertility control on population dynamics found no difference in the population sizes produced by the two methods of sterilisation.
Abstract: We report on a study of confined populations of wild mice in which 67% of females were surgically sterilised to simulate the possible effects of fertility control on population dynamics. Social structure can influence the breeding performance of female mice and, as this may be hormonally controlled, we examined whether the maintenance of hormonal competence by sterilised female mice was necessary to achieve a significant decrease in population size. We compared two methods of surgical sterilisation – tubal ligation, which leaves the animal’s reproductive hormone regulation intact, and ovariectomy, which disrupts the normal regulation of the hormones of the pituitary–ovarian axis. There was no difference in the population sizes produced by the two methods of sterilisation and thus the maintenance of hormonal structure is unlikely to influence the population’s response to fertility control. If anything, the population response to the presence of hormonally competent but sterile females was different from that expected – populations with tubally ligated females had slightly higher growth rates, recruitment of young, and breeding performance, than populations with ovariectomised females. The 67% level of infertility amongst females in the population successfully reduced population size and growth rate when compared with unsterilised populations. This reduction in population size was not related to the level of sterility imposed. Compensation occurred through improved breeding performance of unsterilised females, particularly in the tubally ligated populations.
76 citations
TL;DR: The study has provided little evidence that cane toads have a significant adverse effect in the short-term on the diversity and abundance of the native fauna examined, however, there was an indication that there may be a long-term indirect effect on some fauna.
Abstract: The range of the cane toad has expanded rapidly in the Northern Territory, and there is growing concern that the species may have a detrimental effect on the native fauna. The aim of this study, therefore, was to determine the short-term effects of cane toads on populations of native fauna and, specifically, to compare the species diversity and relative abundance of native fauna before, during and after the invasion of an area by cane toads. Five major groups of fauna (wingless invertebrates, amphibians, reptiles, birds and mammals) were sampled over two years. The study has provided little evidence that cane toads have a significant adverse effect in the short-term on the diversity and abundance of the native fauna examined. However, there was an indication that there may be a long-term indirect effect on some fauna. In the short-term the dingo (Canis lupus dingo) and one Order of insect (Coleoptera) were affected negatively. The possible long-term negative effect was on the small reptile fauna and particularly the small skinks. This may be an indirect effect on their food supply, because the groups affected were those that were considered neither to ingest cane toads nor to be eaten by cane toads.
TL;DR: The distribution and density of red fox populations were investigated in metropolitan Melbourne from 1990 to 1993 as discussed by the authors from sightings reported by members of the public, from spotlight and active den surveys, and from trapping and road kills.
Abstract: The distribution and density of red fox populations was investigated in metropolitan Melbourne from 1990 to 1993. Distribution data were collected from sightings reported by members of the public, from spotlight and active den surveys, and from trapping and road kills. Archival data suggested that resident populations of foxes have been present within the inner metropolitan area since the early 1940s. Contemporary fox populations were found to be extensively distributed throughout the urban area, with few 1-km 2 grids within a 5-km radius of the Central Business District not containing foxes. Density estimates were based on nearest-neighbour analysis of active natal dens in four field sites. Observations of cubs over a 4-year period at 17 dens within the field sites revealed a mean litter size of 4.36 cubs. Mean 4-year density estimates for each field site, immediately after the breeding season, were 0.47–2.55 dens km −2, which was estimated to represent 3–16 foxes km −2. Density estimates may be conservative, as family groups may contain more than one non-breeding adult. The implications of these data are discussed with respect to the potential role of the urban fox in the epidemiology of rabies. It was concluded that fox populations at the field sites were of sufficient density to maintain a sylvatic epizootic of rabies.
TL;DR: Functional response models derived from predator–prey theory were fitted to 3 data-sets describing variation in kill rates with feral pig density to demonstrate that hours per kill increased exponentially as shooting reduced pig populations below threshold densities of approximately 2–6 pigs km–2.
Abstract: Because it achieves rapid reductions in pig density, helicopter shooting is perceived to be a cost-effective option for feral pig control. In order to evaluate the cost effectiveness of the technique and develop predictive models of variation in costs, functional response models derived from predator–prey theory were fitted to 3 data-sets describing variation in kill rates with feral pig density. The data-sets were collected during shooting programs conducted on the Mary River floodplain in northern Australia, and on the Macquarie Marshes and Paroo River floodplain in western New South Wales. Fitted models indicated that variation in kill rates with pig density took the form of a Type 3 functional response for all 3 data sets, kill rates approaching a constant maximum at high pig densities and declining toward 0 at pig densities greater than 0. While maximum kill rates were similar for the 3 shooting programs (average 60.49 kill h–1, range 49.64–76.28), densities below which no pigs would theoretically be killed varied significantly (average 2.79 pigs km–2, range 1.34–5.02). Similar maximum kill rates for the 3 shooting programs indicates that, once located, the time taken by shooting teams to dispatch pigs was relatively constant (0.023 h). Variation in threshold densities below which no more pigs would theoretically be shot, indicates that as the density of pigs was reduced, their vulnerability to shooting teams differed between the 3 shooting programs. This may have reflected differences between sites in either the capacity of resident pigs to learn to evade shooting teams or, more likely, the availability of refuge habitat. For 2 of the shooting programs, too few data were available to estimate the effect of declining pig density on kill rate, precluding detailed examination of differences in the efficiency with which pigs were found (search efficiency). Using estimates of pig density below which no pigs would theoretically be shot to set a limit to the effectiveness of shooting programs, models predicting variation in hours per kill with pig density were derived from each data set. These models demonstrated that hours per kill increased exponentially as shooting reduced pig populations below threshold densities of approximately 2–6 pigs km–2. Generalised models relating variation in cost per kill to pig density for the 3 shooting programs are described.
TL;DR: Prey species previously uncommon in the diet of seals and penguins around Macquarie Island were commonly eaten by Hooker's sea lions, and fish constituted the primary component of the diet.
Abstract: Scats were collected from itinerant male Hooker's sea lions, Phocarctos hookeri, at Macquarie Island and the uneroded faunal remains used to assess the diet. Uneroded sagittal otoliths were used to identify teleost fish and to calculate fish size. Prey items included 14 taxa of teleost fish, cephalopods, gastropods, crustaceans and fur seals. Fish constituted the primary component of the diet. Prey species previously uncommon in the diet of seals and penguins around Macquarie Island were commonly eaten by Hooker's sea lions. The sub-Antarctic horse fish (Zanclorhynchus spinifer) and the Patagonian tooth fish (Dissostichus eleginoides) were the two most abundant species and occurred in 62.5p and 41.7p of all scats respectively. There were no age-specific and individual differences in the diet of sea lions. Seasonal variances in diet were absent. Small plastic fragments (diameter ∼1 mm) were found only in association with otoliths of Electrona subaspera. Some overlap was seen between the diet of itinerant male Hooker's sea lions and the commercial fisheries that currently operate around Macquarie Island.
TL;DR: These trials established that foxes cache 1080 baits, and the location of these caches with respect to original placement and the extent to which these caches are later retrieved and consumed are discussed.
Abstract: Baiting is widely used to control the introduced fox (Vulpes vulpes) in Australia. Caching of baits by foxes was observed through the use of miniature radio-transmitters. Both non-toxic and toxic (1080) baits were used to determine the number of baits cached, the location of these caches with respect to original placement and the extent to which these caches are later retrieved and consumed. These trials established that foxes cache 1080 baits. An average of 34% of transmitter baits offered were taken and 10% were cached. The mean distance from the bait station to the cache was 156 m, with some baits being cached up to 800 m away. Implications of these results for current fox management strategies and the consequences of using bait take as a population index are discussed.
TL;DR: An age-structured population analysis is used to determine recruitment levels and a condition for survival which can assist management decisions and hence improve the viability of populations of northern brown kiwi, Apteryx mantelli, in forests on the New Zealand mainland.
Abstract: An age-structured population analysis is used to determine recruitment levels and a condition for survival which can assist management decisions and hence improve the viability of populations of northern brown kiwi, Apteryx mantelli, in forests on the New Zealand mainland. Currently, in the absence of predator control, recruitment rates are less than 5% due to high levels of stoat, Mustela erminea, predation on juvenile kiwi. Predation levels on adult kiwi are very low. The analysis predicts that a recruitment rate of 19% is required to maintain population stability. To achieve this target, stoat populations have to be reduced by about 80% in some years, and maintained at a critical residual density estimated to be a value less than two animals per square kilometre for up to nine months until immature kiwi reach a safe size of about 1200 g (50% of their adult weight). Recent predator-control initiatives indicate that stoat numbers can be reduced and maintained at low levels in relatively small areas of mainland forest (up to 1000 ha). New techniques are needed to protect kiwi over larger areas.
TL;DR: The diet of New Zealand fur seals was examined by analysing diagnostic remains from 500 faecal samples and 84 regurgitates collected between July 1993 and September 1994, with a seasonal variation in prey composition with arrow squid dominant in summer and autumn.
Abstract: We examined the diet of New Zealand fur seals (Arctocephalus forsteri) at a rookery on Otago Peninsula, New Zealand, by analysing diagnostic remains from 500 faecal samples and 84 regurgitates collected between July 1993 and September 1994. In total, 27 taxa (species or genera) were identified. Small fish were numerically dominant in faecal samples, with five fish species (three species of lanternfish (Myctophidae), ahuru (Auchenoceros punctatus) and juvenile red cod (Pseudophycis bachus)) accounting for over 90% of prey items. Regurgitates occurred only seasonally and contained predominantly cephalopod remains (99% of prey items). Numerical analyses may prove misleading as an indicator of the composition of seal diet because the contribution of large fish that dominate estimates of prey biomass are underrepresented. Estimates of prey biomass were made by combining estimates from both faecal and regurgitate samples. Possible biases created by using this method are considered. A seasonal variation in prey composition was apparent, with arrow squid (Nototodarus sloanii) dominant in summer and autumn, replaced by a combination of barracouta (Thrysites atun), mackerel (Trachurus sp.) and New Zealand octopus (Octopus maorum) in winter and spring.
TL;DR: Results of dietary analyses for 15 extant and one extinct species of Australian desert rodents are provided, indicating that omnivory, over and above any other dietary strategy including granivor, is predominant among rodents inhabiting Australian deserts.
Abstract: Very little systematic information has been collected on the diets of Australian rodents in arid and semiarid regions. The information that is available is restricted generally to short periods of sampling and small sample sizes. Here we review the diets of 15 extant and one extinct species of Australian desert rodents, and provide new results of dietary analyses for (1) Leggadina forresti, Pseudomys desertorand Rattus villosissimus from the Simpson Desert, south-western Queensland, (2) P. albocinereus and P. bolami from the western goldfields of Western Australia, and (3) Notomys alexis, P. desertor and P. hermannsburgensis from the Tanami Desert, Northern Territory. Overwhelmingly, omnivory is the predominant dietary strategy, with most species (11) taking substantial amounts of invertebrate, seed and green plant material. Of the other five species, four can be considered herbivores and one a granivore. Of the four herbivores, however, one is extinct (Leporillus apicalis), one is restricted to an offshore island (Lep. conditor), while another (P. fieldi) is classified as a herbivore from a diet sample of four individuals only. Similarly, P. occidentalis is classified as a granivore on the basis of dietary sampling of two individuals alone. These findings indicate that omnivory, over and above any other dietary strategy including granivory, is predominant among rodents inhabiting Australian deserts.
TL;DR: These findings have important implications for field surveys and how data gathered from such studies are interpreted, if the aim of field survey is to detect a wide range of species then several types of hairtubes may need to be deployed.
Abstract: We compare detection rates of different species of mammals by three types of hairtubes in both the mountain ash forests of the central highlands of Victoria and a range of wet forest types at Tumut in southern New South Wales. The types of hairtubes were a small-diameter PVC pipe, a large-diameter PVC pipe and a newly constructed tapered hair funnel. Data were analysed for brown antechinus (Antechinus stuartii), bush rat (Rattus fuscipes), common wombat (Vombatus ursinus), swamp wallaby (Wallabia bicolor) and common and mountain brushtail possums (Trichosurus vulpecula and T. caninus). The most effective hairtube type (i.e. the one yielding the highest number of detections) varied between species: small hairtubes forR. fuscipes, hair funnels for Trichosurus spp., and large hairtubes for V. ursinus and W. bicolor. For A. stuartii, the most effective hairtube type differed between the two study regions (hair funnels in Victoria and small hairtubes at Tumut). Detection by more than one hairtube type at a given plot was uncommon. Our findings have important implications for field surveys and how data gathered from such studies are interpreted. For example, if the aim of field survey is to detect a wide range of species then several types of hairtubes may need to be deployed.
TL;DR: In this paper, the authors investigated home-range size, utilisation of tree species and patches, and the influence of spacing behavior by females on social organisation of koalas.
Abstract: This study investigated home-range size, utilisation of tree species and patches, and the influence of spacing behaviour by females on social organisation. It was undertaken in south-east Queensland in an area dominated by agricultural activity (beef and dairy cattle and cropping). Extensive clearing in the study area resulted in patches of vegetation that varied in size from less that 1 ha to blocks of 50–100 ha. Eucalyptus tereticornis and E. crebra were the dominant species in these patches and koalas used both species. The average home-range size (delineated by the 95% probability polygon from a kernel estimator) was 34.4 ha and 15.0 ha for males and females respectively; that delineated by the 70% probability polygon was 12.5 ha and 5.0 ha for males and females respectively. Koalas were not reliant on corridor systems and sometimes moved further than 5 km in a season. Koalas have few non-food-related requirements, i.e. they do not need den sites, nest sites, display areas, etc. Furthermore, they do not utilise the understorey and their mobility between patches does not appear to be compromised by the absence of corridors of trees. It is suggested that, in comparison with other arboreal marsupials, it should be relatively easy to provide habitat for koalas within rural areas.
TL;DR: In 1996–97, the density of two populations declined over an expected period of increase, while at the third site the density increased as expected from pre-RHD patterns.
Abstract: Quarterly spotlight counts of rabbits were conducted at three sites in central-western New South Wales. These counts commenced two years before the arrival of rabbit haemorrhagic disease (RHD) in the winter of 1996. The existing data on quarterly rates of change in rabbit abundance for the three populations provided a unique opportunity to study the effects of RHD on rabbit demography. Prior to the arrival of RHD, all three populations underwent phases of sequential increase and decrease in each year. On the basis of these patterns, RHD had a variable influence on the demography of the three rabbit populations. In 1996–97, the density of two populations declined over an expected period of increase, while at the third site the density increased as expected from pre-RHD patterns. Twelve months after their failure to generate expected positive rates of increase the two affected populations had returned to the normal sequence of increases and decreases in density although still at comparatively low numbers.
TL;DR: Rainfall and climate indices generally were most correlated with the species’ abundance and abundance indices for plumed whistling-duck, chestnut teal, hardhead, black swan and black-winged stilt appeared to have decreased between 1983 and 1992, which may correspond to other factors not modelled.
Abstract: We examined the relationships between abundance of 16 species of waterbirds and the rainfall in eastern Australia, the rainfall west of this region, the annual Southern Oscillation index (SOI), the wetland area, and hunting in eastern Australia for the period 1983–92. Data were collected during aerial surveys of eastern Australia. For most explanatory variables, lags of up to five years before aerial surveys were also investigated during these analyses. The analyses covered all nine game species (plumed whistling-duck, Australian shelduck, Australian wood duck, pink-eared duck, grey teal, chestnut teal, Pacific black duck, Australasian shoveler, hardhead) and seven non-game species (Australian pelican, white-faced heron, yellow-billed spoonbill, freckled duck, black swan, black-winged stilt, red-necked avocet). Regression models were developed for all species apart from Australian pelicans. Rainfall and climate indices generally were most correlated with the species’ abundance. Bonferroni adjustments to significance levels meant that there were significant variables in regression models for seven of the 16 species. Abundance indices for plumed whistling-duck, chestnut teal, hardhead, black swan and black-winged stilt were related to the climate variables (rainfall, SOI) and wetland area, whereas abundance of pink-eared duck and red-necked avocets were negatively related. Abundance of chestnut teal was positively related to numbers of hunting licences sold. The results are equivocal about the role of hunting in determining waterfowl abundance, which is probably a reflection of few data points and numbers of variables included. In general, abundance indices of waterbirds appear to have decreased between 1983 and 1992, which may correspond to other factors not modelled
TL;DR: Investigating the way D. lumholtzi used its habitat within a rainforest fragment on the Atherton Tableland, North Queensland found individual animals regularly associated with only a small suite of tree species present within their home range, and appeared to display individual preferences for certain species.
Abstract: Lumholtz’s tree-kangaroo (Dendrolagus lumholtzi), one the largest arboreal mammals in Australia, has been poorly studied owing to its limited distributional range and secretive habits within tropical rainforests. This study investigated the way D. lumholtzi used its habitat within a rainforest fragment on the Atherton Tableland, North Queensland. Thirteen animals were fitted with radio-collars to determine their spatial and temporal use of habitat. Female D. lumholtzi used exclusive home ranges averaging 0.7 ha in area (90% harmonic mean), while males occupied larger home ranges of an average of approximately 2 ha, allowing for a density of 1.4–1.5 adult tree-kangaroos per hectare within the study area. The exception to this home- range size was one juvenile male presumably undergoing post-natal dispersal that used several forest fragments and other habitats, with a home range of 332 ha. Home ranges of males overlapped in part the ranges of several females. Home ranges of males tended to abut those of other males, and antagonistic encounters occurred at the boundaries of the home ranges. Males had a significantly larger body size than females (males 8.63 kg; females 7.05 kg). Social interactions between individuals, apart from antagonistic male–male encounters, were observed infrequently. Only 6% and 2.7% of fixes for females and males, respectively, included the presence of another animal in the same or adjacent tree at the time of location. Lumholtz’s tree-kangaroos were associated with a wide range of rainforest trees and a smaller number of vine species. However, in general, individual animals regularly associated with only a small suite (mean 3.5 species with >10% usage) of tree species present within their home range, and appeared to display individual preferences for certain species. Individual radio-tracked D. lumholtzi were visible only 9.4% of the time at night, and 20% of the time during the day. Males and females were as visible as each other, and both were seen significantly lower in the canopy and into the mid-storey during the night than during the day.
TL;DR: The high rates of bait uptake in this study are encouraging and suggest that oral vaccination of foxes by baiting may be a viable strategy for rabies containment in urban areas and is worthy of further assessment at reduced baiting densities.
Abstract: Red foxes (Vulpes vulpes) are widely distributed throughout the Melbourne metropolitan area. Density estimates indicate that fox populations would be capable of maintaining the endemic persistence of rabies. Oral vaccination of foxes by baiting is a technique that has been used successfully overseas to manage rabies epizootics. This study assessed the uptake by foxes of baits containing biomarkers in three urban field sites in winter 1993 and summer 1993/94. Baits were dosed with 200 mg of tetracycline in the winter trial and 5 mg of iophenoxic acid in the summer trial, and distributed at a density of 8 baits ha −1 in open areas within each field site. In the winter trial, 8 of 11 (72.7%) radio-collared foxes known to be in the field sites during the distribution of baits were marked. In the summer trial, 45 of the 49 foxes (92%) recovered from the combined field sites had consumed at least a single bait, resulting in bait acceptance of 80–97% for each field site. No bias existed between plasma iodine levels due to sex, although first-year foxes had a significantly higher level than older age groups combined. There were no significant differences in mean age of foxes collected at the three field sites, yet significant differences existed in mean plasma iodine concentrations between all three sites. These results are discussed with reference to rabies contingency planning. The high rates of bait uptake in this study are encouraging and suggest that oral vaccination may be a viable strategy for rabies containment in urban areas and is worthy of further assessment at reduced baiting densities.
TL;DR: The former distributions of stick-nest rats (Leporillus conditor and L. apicalis), both extinct on the Australian mainland since about the 1930s, were determined from literature reports, museum records, interview responses and field surveys of key areas.
Abstract: The former distributions of stick-nest rats (Leporillus conditor and L. apicalis), both extinct on the Australian mainland since about the 1930s, were determined from literature reports, museum records, interview responses and field surveys of key areas. Population parameters were determined for L. conditor from early literature accounts, studies of remnant stick-nests in caves, a three-year study of the last known naturally-occurring populations on the Franklin Islands, records maintained for a captive-breeding program since 1986, and further population data obtained during systematic monitoring of reintroduced populations. Comparable data for L. apicalis could be obtained only from early literature accounts and remnant stick- nests in caves; this species has not been recorded since 1933 and is presumed extinct. Leporillus conditor is a predominantly ground-dwelling, herbivorous rodent of semi-arid, perennial shrubland habitats, which builds nests of interwoven sticks for protection from the elements and from predators. Leporillus apicalis apparently occupied similar habitats, often in sympatry with L. conditor, but extended its range further into the arid zone and may have had a more arboreal life-style and a more diverse diet, including invertebrates. The demise of both species from the mainland was almost certainly due to severe habitat degradation caused by introduced herbivores (mainly rabbits and sheep) before, and leading into, severe drought conditions. The resulting reduction in availability of food and cover also led to an increased vulnerability to predation (primarily by foxes, cats, dingoes and owls). In current L. conditor populations, females reproduce throughout the year and have well-defined home- ranges with relatively small core activity areas. Males have considerably larger home ranges. Predation by owls, especially barn owls (Tyto alba) is a significant cause of Leporillus mortalities, highlighting the importance of cover for the rats’ survival.
TL;DR: The responses of free-ranging brownsnakes to 455 close encounters with a human observer, using 40 snakes implanted with miniature radio-transmitters, plus encounters with non-telemetered animals are recorded to suggest ways in which people can reduce the incidence of potentially fatal encounters with brownsnake.
Abstract: Eastern brownsnakes (Pseudonaja textilis) are large (to 2 m), slender, dangerously venomous elapid snakes that cause significant human mortality. We recorded the responses of free-ranging brownsnakes to 455 close encounters with a human observer, using 40 snakes implanted with miniature radio-transmitters, plus encounters with non-telemetered animals. Our study area (near Leeton in south-eastern Australia) is typical of many of the agricultural landscapes occupied by P. textilis. Contrary to public opinion, the snakes were rarely aggressive. About half of the encounters resulted in the snake retreating, and on most other occasions they relied on crypsis. Snakes advanced towards the observer on only 12 occasions (<3% of encounters) during initial approach, and only three of these advances were offensive. The snakes’ responses to an approach depended on the observer’s appearance (e.g. snakes were more likely to ignore an observer wearing light rather than dark shades of clothing) and behaviour (e.g. snakes were more likely to advance if approached rapidly, and touched immediately). Snakes were more likely to retreat if they were sub-adult rather than adult, if they were warm, or if they had been moving prior to an encounter. Weather conditions (air temperature, wind velocity and cloud cover) also influenced the snakes’ responses, as did season and time of day. The snakes’ response was relatively predictable from information on these factors, enabling us to suggest ways in which people can reduce the incidence of potentially fatal encounters with brownsnakes. ‘Snakes are first cowards, next bluffers, and last of all warriors’ (Pope 1958)
TL;DR: Two disparate populations of Pseudomys australis, in the southern and north-western Lake Eyre Basin of South Australia, were studied over a 3-year period using trapping and radio-tracking techniques, finding differences appeared to relate to the availability and distribution of food and shelter in the respective locations.
Abstract: Two disparate populations of Pseudomys australis, in the southern and north-western Lake Eyre Basin of South Australia, were studied over a 3-year period using trapping and radio-tracking techniques. Various aspects of the species’ ecology were investigated. Past records of the species were almost always associated with population irruptions following exceptionally wet years. Aspects of population dynamics, fine-scale habitat use, activity ranges and burrows were studied and related to habitat condition during three dry seasons following a good season. Both areas were associated with floodout plains in a gibber desert environment but differed in soils and vegetation structure. The population dynamics and structure and home-range activity also differed. These differences appeared to relate to the availability and distribution of food and shelter in the respective locations. The differences between populations in the two areas are discussed with reference to the source/sink and refugia concepts.
TL;DR: Changing the bait type would appear to hold the greatest promise for overcoming aversions by possums to cereal bait.
Abstract: The current experiment aimed to determine the proportion of wild-caught possums from previously poisoned and non-poisoned populations that developed aversions to 1080 baits. In addition, we aimed to identify the bait characteristics mediating the ongoing aversions. In an initial test, animals from areas previously exposed to a 1080 control-operation avoided 1080 baits (60–80%), whereas few naive animals (0–20%) avoided these baits. The baits comprised a green-dyed, cinnamon-lured cereal loaded with 0.08% 1080. As a result of the exposure to the toxic baits, over 80% of the naive animals subsequently developed aversions to those baits. Sixty-nine of these averse animals were allocated to one of 16 bait-treatment groups in a factorial design balanced for population, sex, age and bodyweight. Each bait was characterised by four factors: (a) presence or absence of 1080, (b) presence or absence of green dye, (c) lure type (cinnamon or orange), and (d) bait type (No. 7 or carrot). The presence or absence of 1080 or green dye did not influence the degree of bait avoidance. Lure type had a significant effect on consumption, with 53% of possums avoiding an orange bait compared with 73% for cinnamon baits. Bait type also had a significant effect on avoidance rates, with carrot baits being avoided by 42% of possums compared with 83% for No. 7 baits. Changing the bait type would appear to hold the greatest promise for overcoming aversions by possums to cereal bait.
TL;DR: It is shown that the yellow-bellied glider is reliant on sap as a food resource but particularly so at both ends of its geographic range, and not on a diversity of tree species nor on a winter-flowering species.
Abstract: This study provides the first assessment of the diet of the yellow-bellied glider (Petaurus australis) in the south-west portion of its range near the Victorian–South Australian border. Examining its diet in this region is viewed as being fundamental to understanding the ecological requirements of the species. Observations were conducted over a five-year period on gliders from five distinct groups. Sap was the most important food item throughout the year and accounted for 83% of 407 feeding observations. Each group of gliders used up to 21 different trees for sap, but during any sample period only 1–8 trees were used. This represents a vastly different pattern of use of sap trees to that described in any earlier study. Some trees were visited more often than others, and these tended to be heavily scarred, indicating use over many years. Other food types were arthropods and honeydew and, to a lesser extent, nectar. This study also revealed that the yellow- bellied glider is not dependent on a diversity of tree species nor on a winter-flowering species. We provide a review of the diet of the yellow-bellied glider throughout its range. This shows that the yellow-bellied glider is reliant on sap as a food resource but particularly so at both ends of its geographic range. The reason for this is unclear, but there is definitely a need for further study of sap-flow patterns in eucalypts.
TL;DR: The conclusion from this study is that males maintained a large, unvarying, home range to maximise access to females while females changed their home-range size according the abundance of food and the constraints of high temperature.
Abstract: In this study the home-range sizes of feral pigs (Sus scrofa) at Nocoleche Nature Reserve, semi-arid New South Wales were measured by radio-telemetry over the course of a drought. The abundance of food was indexed simultaneously by the amount of pasture in the four most common habitats at Nocoleche (shrubland, woodland, riverine woodland, and ephemeral swamps). The influence of the pig's sex, and mean maximum temperature and pasture biomass on the home-range size of pigs were examined using ANOVA and multiple regression, respectively. Mean home-range size of males was 7.9–11.6 km2 and that for females was 4.2–8.0 km2 . Males had significantly larger home ranges than females, and their home-range size did not change significantly over the course of the drought. In contrast, the size of the home ranges of females changed significantly and was correlated negatively with the abundance of pasture biomass in shrublands and mean maximum temperature, and positively with the abundance of pasture biomass in ephemeral swamps. The conclusion from this study is that males maintained a large, unvarying, home range to maximise access to females while females changed their home-range size according the abundance of food and the constraints of high temperature.