bluuebunny/crossref_metadata_2025 huggingface dataset:
Models of the distribution and abundance of ground-dwelling mammals in the eucalypt forests of north-eastern New South Wales in relation to environmental variables
Authors: Catling P. C. , Burt R. J. , Forrester R. I.
Published: March 2003

Statistical models are presented of the distribution and abundance of ground-dwelling mammals in eucalypt forests in relation to environmental variables within an area of approximately 24 000 km2 in north-eastern New South Wales. Environmental variables are defined as climatic or topographic variables that may be useful to map the distribution of fauna. The environmental variables examined were season, temperature, rainfall, elevation, lithology, steepness of slope, position on slope, aspect and landform profile. The probability of recording some species was higher in spring than autumn and many species were in highest abundance in areas of low temperature (high elevation). Although aspect was a significant variable in a number of models, no species was absent from any aspect category. Mid-slopes down to and including creeks and drainage lines were particularly important for many species, as were areas with flatter terrain. Although we have modelled environmental variables only there will no doubt be longer-term interactions between habitat and environmental variables. Fundamentally, environmental variables will determine the type of habitat present at a site, and the distribution of canopy communities, at least, can be predicted from environmental variables. However, other studies have shown for ground-dwelling mammals that environmental variables contribute little and it is the state of the habitat locally, and particularly the understorey, that determines their presence and abundance at a site. The results are discussed in relation to similar models using habitat variables and in relation to the use of such models in the management of ground-dwelling fauna in forests.
Do European rabbits (Oryctolagus cuniculus) influence the population ecology of the burrowing bettong (Bettongia lesueur)?
Authors: Robley Alan J. , Short Jeff , Bradley Stuart
Published: March 2003

The influence of the European rabbit (Oryctolagus cuniculus) on the survival of medium-sized native mammals remains unclear despite 60 years of speculation. Most medium-sized native species that might have been affected by the presence of rabbits are extinct, rare, or endangered. This limits the opportunity to study their interaction with introduced herbivores. We studied the effect of changes in rabbit density on aspects of the ecology of burrowing bettongs (Bettongia lesueur) reintroduced to mainland Australia on Heirisson Prong, Shark Bay, Western Australia. The rabbit population at the site grew to a 10-year high concomitant with a dry summer and low and declining pasture cover. Rabbit browsing led to widespread defoliation of, and subsequent death of, many palatable shrubs. Despite these adverse conditions, reproduction, recruitment and rate of increase of bettongs did not vary with changes in rabbit density, nor did the survival of adult males and females. This work casts doubt on the idea that competition with an introduced herbivore, such as the rabbit, was an important factor in the decline of the burrowing bettong. It highlights the need to understand the ecologies and life histories of native and introduced species in order to manage for the long-term persistence of native species.
Origin and spread of the cat, Felis catus, on mainland Australia, with a discussion of the magnitude of its early impact on native fauna
Authors: Abbott Ian
Published: March 2003

A comprehensive search of historical sources found no evidence that the cat,
Felis catus, was present on mainland Australia prior to
settlement by Europeans. Nor were records of cats found in journals of
expeditions of exploration beyond settled areas, undertaken in the period
1788–1883. Cats did not occupy Australia from the earliest point of
entry (Sydney, 1788), but instead diffused and were spread from multiple
coastal introductions in the period 1824–86. By 1890 nearly all of the
continent had been colonised. This new chronology for the feline colonisation
of Australia necessitates a re-appraisal of the early impact of the cat on
native mammal and bird species. The evidence for early impacts of cats causing
major and widespread declines in native fauna is considered tenuous and
unconvincing.
Reproductive demographics among brush-tailed phascogales (Phascogale tapoatafa) in south-western Australia
Authors: Rhind S. G.
Published: March 2003

Reproduction and population demographics were examined among wild brush-tailed phascogales in southern Western Australia. Data were gathered in a single region during 1992–97 from 387 individuals, 139 of whom were monitored by radio-telemetry. In contrast to Victorian phascogales, which all have eight teats, the Western Australian population contained females with six (30%), seven (21%), and eight (49%) teats (n = 72). Teat numbers varied between mothers and daughters/sisters, which appears unprecedented among dasyurids. The data strongly suggest that females try to raise as many young as they have teats. Population changes are as described for Victorian phascogales: complete male die-off occurs in July; some females survive to breed in a second year; and there is long-distance male dispersal and high philopatry by female offspring. Births occur from July to September, somewhat later and also less synchronised than among Victoria phascogales. Late breeding by females in one year suggests that sperm storage may be extensive in this species. Strong associations between the physical condition of females and rainfall suggest that these may influence between-year variation in birth times and sex-ratio bias in litters. Similarly, poor physical condition of young during drought may have underpinned atypical dispersal behaviour in males. Decreased teat numbers and smaller litter sizes indicate that phascogales from south-western Western Australia are reproductively adapted to relatively low food availability. However, this species experiences difficulty successfully breeding and rearing young under drought conditions.
The effect of drought on body size, growth and abundance of wild brush-tailed phascogales (Phascogale tapoatafa) in south-western Australia
Authors: Rhind S. G. , Bradley J. S.
Published: March 2003

Body size and growth data were gathered on 387 wild brush-tailed phascogales captured between 1992–1997 in south-western Australia. This marsupial has not previously been studied in Western Australia. Compared with Victorian phascogales, those in the south-west (single region) are typically 20–30% smaller in mass, smaller in skeletal measurements, and sexual size dimorphism is less. Habitat quality was correlated with body size and the largest phascogales were found in swamp/gully systems. These findings suggest food is a normally limiting resource for this species in the south-west environment. Additionally, a significant decrease in growth and size occurred during a drought year (1994), and growth of young seemed restricted during dependency. Maternal mortality appeared high during late lactation as orphaned, unweaned young were encountered in nest boxes. In 1995 adult males were 25% less in mass than usual; females 15% less. Population decline followed and by 1996 capture rates were 1/3 of that typically found for the time of year. Recovery was not apparent until two years after drought (early 1997). In this food-limited environment phascogale populations appear particularly vulnerable to annual fluctuations in rainfall.
Effect of a control burn on lizards and their structural environment in a eucalypt open-forest
Authors: Singh Sarinda , Smyth Anita K. , Blomberg Simon P.
Published: March 2003

The composition of an open-forest lizard assemblage in eastern Australia was examined before and after a low-intensity controlled fire and concurrently compared with that in an adjoining unburnt area. The effect of fire on the available structural environment and the habitat used by two focal species, Carlia vivax and Lygisaurus foliorum, was also examined. Lizard species richness was unaffected by the controlled burn as was the abundance of most species. C. vivax was the only species to display a significant reduction in abundance after fire. While the low-intensity fire resulted in significant changes to the available structural environment, there were no compensatory shifts in the habitat preferences of either C. vivax or L. foliorum. The reduction in abundance of C. vivax was congruent with this species' avoidance of burnt areas. C. vivax displayed a non-random preference for ground cover and litter cover, which were reduced in burnt areas. Changes in the availability of preferred structural habitat features are likely to contribute to changes in the abundance of some lizard species. Therefore, even low-intensity disturbances can have an impact on lizard assemblages if critical habitat features are lost or become limiting.
Predation rates of artificial nests in the edge and interior of a southern Victorian forest
Authors: Berry Lainie
Published: March 2003

Predation rates of nests at human-induced habitat edges may be greater than in forest interior due to differences in predator assemblages and predator activity. I compared the predation rates on 192 artificial nests containing plasticine eggs placed in forest edge and interior sites at Bunyip State Park, Victoria. The nest-predation rates at the forest edge sites were significantly greater (mean = 52–58%) than that at the forest interior sites (mean = 30–39%). The relative rates of predation by birds compared with mammals were significantly greater at forest edge sites (mean = 78–94%) than at forest interior sites (mean = 36–67%). Higher rates of nest predation at forest edges appeared to be due to greater densities of avian predators such as the grey shrike-thrush (Colluricincla harmonica), and/or lower abundances of small mammals. However, biases towards certain predator types may mask real, or create false, patterns in predation rates of artificial nests. A better understanding of how predators respond to artificial nests compared with natural nests is required. Until then, results of predation studies that use artificial nests should be interpreted with caution.
Pre-sowing control of house mice (Mus domesticus) using zinc phosphide: efficacy and potential non-target effects
Authors: Brown Peter R. , Chambers Lisa K. , Singleton Grant R.
Published: March 2003

Zinc phosphide was tested on populations of house mice in cereal stubble and
pasture paddocks in the Central Mallee region of Victoria, in Autumn 1997.
There were three replicates of two application methods: aerial and ground
(perimeter) baiting. The response of mouse populations to baiting was
monitored by live-trapping; estimates of population size and survivorship were
compared between baited and unbaited sites (n =
3) taking prebaiting population sizes into account. Zinc phosphide was
effective in decreasing the abundance (adjusted trap success) of mice on
aerially baited sites (by 51%), but the reduction observed on
ground-baited sites (24%) was not significant. There was no change in
abundance on the untreated sites. There was a significant reduction in the
survivorship of mice on both aerially and ground-baited sites compared with
unbaited sites. Non-target species were monitored before and after baiting.
Only four bird deaths were recorded as a result of the baiting program. Given
that birds are highly mobile, with deaths possible many kilometres from the
bait sitesit was difficult to fully assess the impact of poisoning on bird
species in the area without more rigorous searching of vegetated areas further
from baited paddocks.
Effects of habitat fragmentation on the demography, movements and social organisation of the eastern pygmy-possum (Cercartetus nanus) in northern New South Wales
Authors: Bladon R. V. , Dickman C. R. , Hume I. D.
Published: March 2003

A population of eastern pygmy-possums
(Cercartetus nanus) was studied in northern New South
Wales for almost 3 years. A total of 98 pygmy-possums was captured, of which
52 were captured only once. The sex ratio of the population did not differ
significantly from parity. Mid-way through the study, 1.4 ha of the 4.0-ha
study site was cleared.
Pre-clearing capture rates in nest boxes averaged 33.5 ± 5.8 captures
per 100 box checks per month, and the population was estimated by three
methods to be at least 15–20 animals. There was no significant
difference in body mass between adult males (23.7 ± 6.3 g) and adult
females (27.1 ± 7.7 g). Males had significantly larger short-term home
ranges (0.35 ± 0.14 ha) than females (0.14 ± 0.06 ha) and tended
to move over greater distances each night. Breeding occurred from summer to
early winter, and juveniles and sub-adults entered the population in autumn
and winter. The mean number of pouch young was 3.9. The most likely minimum
size at which juveniles left their mother was 9–11 g. Adult body mass
and condition were highly variable over time, and did not appear to be related
to either the breeding season or Banksia flowering.
Fourteen pygmy-possums were found torpid during the study. Population troughs
occurred in late winter and spring and were associated with low survival
and/or seasonal migration, possibly linked to the cessation of
Banksia flowering in July and the lack of alternative
food sources at this time and/or increased use of nest boxes by
Antechinus stuartii during late winter. Post-clearing,
capture rates fell to 7.8 ± 1.6 captures per 100 box checks per month,
the estimated population size fell to 5–8 animals, and there was an
almost total lack of juvenile/sub-adult recruitment into the population.
The results support concerns that the long-term survival of the eastern
pygmy-possum in New South Wales is threatened by continued land clearing
throughout much of its present range.
Foraging ecology of the agile wallaby (Macropus agilis) in the wet - dry tropics
Authors: Stirrat Simon C.
Published: March 2003

Seasonal changes in diet composition and diet preferences of the agile wallaby (Macropus agilis) were investigated in East Point Reserve, Darwin. The wallabies were almost exclusively grazers in the wet season when the nitrogen content and in vitro digestibility of herbage were high. Evidence suggests that wallabies rarely browsed in the wet season. The diet consisted mainly of non-leguminous forbs, reflecting the abundance of these plants in the study site, but the wallabies showed higher preference for grasses and legumes. In the dry season herbage quality was poor and the wallabies grazed on available green grasses and forbs but also broadened their diet considerably to include a range of alternative foods, including browse, leaf litter, fruits, flowers and roots. A flexible foraging strategy allows agile wallabies to exploit a range of resources in this highly seasonal environment where periods of food shortage may be long and their duration unpredictable.
Efficacy of hair-sampling techniques for the detection of medium-sized terrestrial mammals. I. A comparison between hair-funnels, hair-tubes and indirect signs
Authors: Mills D. J. , Harris B. , Claridge A. W. , Barry S. C.
Published: March 2003

We compared the efficacy of two different designs of hair-tube for detecting medium-sized, terrestrial marsupials in a range of forest types in south-east New South Wales. The two designs compared were a large-diameter PVC pipe (large hair-tube) and a tapered hair-funnel. In addition, the relative abundance of forage-diggings of the same marsupials was estimated simultaneously in order to provide an independent assessment of their distribution within the same study area. Only two hair-tubes out of 620 contained hair that could be attributed to the target fauna, both from the long-nosed bandicoot (Perameles nasuta). This was despite the widespread occurrence of forage-diggings at all of the 31 transects that were surveyed. Only two species of mammal, the agile antechinus (Antechinus agilis) and the bush rat (Rattus fuscipes), were detected in sufficient quantity to enable statistical analysis comparing the efficacy of the two hair-tube types. For R. fuscipes the large hair-tube was significantly more effective than the hair-funnel. Conversely, the hair-funnel was significantly more effective in detecting A. agilis than the large hair-tube. Our results suggest that both designs of hair-tube, in their current form, are ineffective for surveying for medium-sized terrestrial marsupials. We see three important issues regarding hair-tube design and implementation that require more attention before this technique can be considered an effective surveying tool: hair-tube morphology, the material used to capture hair, and bait type.
Trends in abundance of New Zealand fur seals, Arctocephalus forsteri, at the Neptune Islands, South Australia
Authors: Shaughnessy P. D. , McKeown A.
Published: March 2003

At the Neptune Islands in early February 2000 at the end of the 1999–2000 pupping season, the abundance of New Zealand fur seal pups was determined using a mark–recapture technique in large colonies and by direct counting in small ones. Pups (n = 2355) were marked by clipping hair on the head to reveal light-coloured underfur. At the North Neptune group, there were 4221 pups and at the South Neptune group 1767 pups, making a total of 5988 pups for the Neptune Island group as a whole. At the North Neptune Islands, pup numbers increased by 53% since February 1993, from 2756 to 4221. For the South Neptune group, pup numbers decreased by 6.7%, from 1893 to 1767. The decrease was spread over most colonies on the island. The large increase in pup numbers at the North Neptune group indicates that the population there is in the recolonisation phase of growth; at the South Neptune group, the fur seal population is likely to be in the maturity phase, with fluctuations in size expected in the future. The Neptune Island group supports the largest aggregation of pinnipeds in Australia.
Breeding dynamics of koalas in open woodlands
Authors: Ellis W. A. , Hale P. T. , Carrick F.
Published: March 2003

The spatial and breeding dynamics of koalas in sub-tropical woodlands at Blair
Athol in central Queensland were intensively monitored between 1993 and 1998.
Genetic relationships among koalas at this locality were studied to determine
the breeding dynamics of males, including whether ‘resident’ or
‘transient’ males dominate as sires. Males and females were
radio-collared and tracked periodically throughout each year of the study.
Genotypes from hypervariable microsatellite loci identified uniquely all
individuals and were used to analyse parentage as well as to determine
population genetic parameters when compared with other regional localities.
Koalas at Blair Athol comprise a population in genetic equilibrium. Gene
diversity estimates show the population to be similar to other populations
found in similar habitat in the region, and estimates of genetic
differentiation among four regional populations showed that gene flow conforms
to a model of isolation by distance. Analysis of parentage found that both
resident and transient males sired about equal numbers of offspring. Familial
DNA analysis revealed multiple paternities of successive young in this
population. The conclusion from this study is that ‘resident’
status among males does not confer any advantage for parentage.
Plot placement when using a passive tracking index to simultaneously monitor multiple species of animals
Authors: Engeman Richard M. , Pipas Michael J. , Gruver Kenneth S. , Bourassa Jean , Allen Lee
Published: March 2003

We evaluated a passive tracking index (PTI) when plots were placed on lightly
used dirt roads versus placement on naturally occurring bare ground in natural
habitat. PTIs were calculated before and after removal of coyotes and some
non-target species during another study that evaluated capture devices. Six
mammals were simultaneously monitored with the PTI: coyotes, raccoons,
white-tailed deer, feral swine, javelina, and rabbits. PTIs from road plots
were significantly higher than from off-road plots, except for deer and
javelina, for which no differences were detected. After removal of coyotes,
PTIs were significantly lower, both from on- and off-road plots. For coyotes
and raccoons, the decline in index values primarily reflected population
reductions. For animals hunted for sport (deer, swine, javelina), population
reductions were minor compared with coyotes, and their declines in index
values likely reflected conditioned responses to the activity and shooting
that accompanied evaluations of the capture devices. We conclude that the PTI
is sensitive to changes in population or changes in activity in response to an
event for a variety of species, and it is most useful when placed on lightly
used dirt roads.
Trapping efficiency of Ugglan traps and Longworth traps for house mice in south-eastern Australia
Authors: Jacob J. , Ylönen H. , Hodkinson C. G.
Published: March 2003

Small mammal studies require traps that efficiently capture the target
species, are cheap, and preferably have no adverse effects on the animals. We
compared the trapping efficiency of Ugglan multiple-capture live-traps with
Longworth single-capture live-traps in field studies of house mice
(Mus domesticus) in the Victorian Mallee of
south-eastern Australia. More captures and recaptures were made with Longworth
traps and fewer mice died while in these traps. There was no difference in
mean body mass of captured mice between Ugglan and Longworth traps but
relatively more males were trapped with Ugglan traps. The trapping mechanism
that requires the mouse to activate a trap door, and open mesh wire along the
sides of the Ugglan trap may be the main reasons for low trappability. In
addition, the open sides could have contributed to the lower survival observed
for mice in Ugglan traps. Although Ugglan traps have the potential for
multiple captures, are cheaper, and their trapping mechanism is less prone to
failure than Longworth traps, they were not as efficient in trapping house
mice at low and medium densities.
Chick survival in the megapode Alectura lathami (Australian brush-turkey)
Authors: Göth Ann , Vogel Uwe
Published: March 2003

Megapode chicks live independently from the time of hatching and are thus ideal subjects for investigations into how the lack of parental care can affect chick survival. Here, we present such results for chicks of the Australian brush-turkey (Alectura lathami), radio-tracked in two smallremnant rainforest patches (Mary Cairncross Rainforest Park and Aplin Forest) from their second day of life. Mortality was 88–100% during the first three weeks after hatching. It did not differ between two breeding seasons at Mary Cairncross Rainforest Park, as evident from comparisons of average survival time (in days) and Kaplan–Meier survival estimates. Survival differed, though, between the two sites in the same breeding season: the average survival time was significantly higher at Aplin Forest (8 days compared with 3�days) and the Kaplan–Meier survival estimates decreased less sharply. Predation by cats and birds of prey exerted the greatest influence on survival, but the proportion of deaths caused by these two predators was approximately the same at both sites. The main factor affecting survival was obviously the availability of thickets, which were more abundant at Aplin Forest. The survival rates of chicks released in thickets was significantly higher than of those released in the rainforest, presumably because they were better protected from predators. For chicks living in thickets the likelihood of being killed was lower than expected, but it was higher for those remaining in rainforest. On the basis of these results, we propose that management plans for endangered megapodes should include the identification and protection of large protective thicket habitats for enhancing overall chick survival, apart from controlling introduced predators such as feral cats.
Validating two methods for monitoring population size of the European rabbit (Oryctolagus cuniculus)
Authors: Ballinger Andrea , Morgan D. G.
Published: March 2003

Two methods commonly used to monitor population sizes of the wild European rabbit (Oryctolagus cuniculus) are spotlight transect counts and active burrow-entrance counts. The accuracy and precision of these techniques were assessed by comparing monitoring data with population estimates derived from intensive observation of a tagged rabbit population near Melbourne, Australia. Both monitoring methods proved capable of yielding population indices linearly related to population density and robust to seasonal changes in population dynamics. The influence of environmental and temporal variables on rabbit emergence, and hence on spotlight transect data, was also investigated. By using data collected over a wide range of weather conditions, 55% of the variation in evening emergence behaviour of rabbits could be predicted by environmental and temporal factors, with solar time, precipitation, air temperature and wind speed accounting for most of this. However, the precision of spotlight transect count data, which are routinely collected at a fixed time of night under mild weather conditions, was not improved by attempting to correct for the effects of weather and time on emergence; continuing to conduct counts under such conditions was supported as a reliable practice.
Habitat selection by adult female eastern grey kangaroos
Authors: Moore Benjamin D. , Coulson Graeme , Way Sarah
Published: March 2003

We determined patterns of habitat selection in the winter–spring period by adult female eastern grey kangaroos (Macropus giganteus) at Yan Yean Reservoir Catchment near Melbourne, Victoria, during 1994–95. We assessed habitat selection at two levels by radio-tracking 11 adult female kangaroos. The 95% isopleth harmonic mean home-range size (mean = 62.3 ha) was the smallest recorded for female eastern grey kangaroos. No range encompassed all of the habitat types available in the study area, and the mix and rankings of habitats selected at this level varied amongst individuals when compared by compositional analysis with available habitats. Selection of habitats at the within-range level also varied among individuals and differed between night and day for many individuals, but not for the population mean. Individuals selected strongly for good foraging habitat within their ranges. In particular, grassy clearings were used by all individuals and were selected strongly by day, night or at both times.
Effects of tropical rainforest roads on small mammals: fragmentation, edge effects and traffic disturbance
Authors: Goosem M.
Published: March 2003

In north-eastern Queensland, impacts on small mammals of traffic disturbance were compared with those caused by physical presence of rainforest roads by trapping in the rainforest interior and adjacent to narrow, unsealed roads with traffic volumes of 264 ± 71 or 4.2 ± 1 vehicles per day. Of the three small mammal species that were most commonly trapped, the proportion and abundance of native Rattus sp. increased at higher-traffic and decreased at lower-traffic sites; the abundance of Melomys cervinipes was relatively constant at both traffic treatments and in the forest interior, and Uromys caudimaculatus decreased at higher-traffic treatments. Road crossings by the smaller rodents, Rattus sp. and M. cervinipes, were primarily influenced by the presence of the road, rather than increased levels of traffic, as crossings were significantly inhibited at both traffic treatments compared with the forest-interior control and there was no difference between traffic levels. Crossings by the larger, more mobile U. caudimaculatus were unaffected by road presence or traffic level. Therefore, increased traffic volume did not appear to affect small mammal movements or community structure. However, since higher traffic levels were not constant throughout the peak periods for activity of these nocturnal species, further investigations are required to determine whether constant nocturnal traffic disturbance may further restrict road crossings by small mammals and alter community structure adjacent to roads.
The acceptability of three types of predator baits to captive non-target animals
Authors: Martin G. R. , Twigg L. E. , Marlow N. J. , Kirkpatrick W. E. , King the late D. R. , Gaikhorst G.
Published: March 2003

The acceptability of three types of non-toxic predator baits to a variety of indigenous non-target species was determined in the laboratory. The bait-types tested were: Dried Meat Bait (DMB), Probait and two sizes of FoxOffTM baits (30 g and 60 g). The potential poisoning risk, if the baits had been toxic, was calculated for each species from their consumption of non-toxic bait and their sensitivity to 1080. Three species consistently sampled baits; Dasyurus geoffroii, Trichosurus vulpecula and Rattus fuscipes. Where species have had exposure to fluoroacetate-bearing vegetation, their consumption of bait and their level of tolerance to 1080 was such that only 2 of 15, 4 of 15, and 3 of 6 species were considered to be potentially at some risk from toxic DMBs, Probait, and FoxOffTM baits, respectively. In contrast, and mainly because of their lower tolerance to 1080, the theoretical risk for those species without evolutionary exposure to fluoroacetate-bearing vegetation was such that 6 of 12, 8 of 12, and 8 of 9 species theoretically face a high or moderate risk from 3-mg DMBs, Probait, and FoxOffTM baits, respectively. We emphasise, however, that theoretical risk does not necessarily equate to a practical risk, and these results are best used to determine which non-target species should be monitored at the population level during predator-control operations. Factors affecting the potential risk to non-target indigenous animals, and some cautions when extrapolating data from laboratory-based studies to the field situation, are discussed.
The impact of murine cytomegalovirus (MCMV) on enclosure populations of house mice (Mus domesticus)
Authors: Farroway L. N. , Singleton G. R. , Lawson M. A. , Jones D. A.
Published: March 2003

Feral house mice are a significant agricultural pest in south-eastern
Australia. Fertility control is favoured as a long-term control strategy,
using murine cytomegalovirus (MCMV) as a viral delivery system for an
immunocontraceptive. We examined the impact of one and two non-sterilising
field strains of MCMV on populations of house mice housed under semi-natural
conditions. MCMV had no effect on the proportion of females pregnant or
lactating or on the number of placental scars per female. However, females in
enclosures with two strains of MCMV produced fewer litters. No impact of MCMV
was detected on adult survival, with high survival (>95%) detected
in all enclosures. Similar numbers of the first cohort of young entered the
trappable population of all enclosures. There was no significant impact of
MCMV on survival of young mice, although there was a trend for reduced numbers
of the second cohort of young and less successful recruitment in enclosures
with two strains of MCMV. The two cohorts of young mice in enclosures with
MCMV had poorer body condition. These impacts of infection on young mice imply
that MCMV may have negative effects on survival only when the host immune
system is not fully developed or the host is immunocompromised. Overall, there
was no effect of MCMV on the rate of increase of the mouse populations.
Therefore, the effects of MCMV were minor at a demographic level, confirming
the suitability of an Australian field strain of MCMV as a vector for an
immunocontraceptive of mice.
Behaviour, coagulopathy and pathology of brushtail possums (Trichosurus vulpecula) poisoned with brodifacoum
Authors: Littin K. E. , O'Connor C. E. , Gregory N. G. , Mellor D. J. , Eason C. T.
Published: March 2003

Brodifacoum is a second-generation anticoagulant rodenticide used widely for controlling brushtail possums (Trichosurus vulpecula) in New Zealand. We determined its toxic effects on possums to make inferences about the welfare of brodifacoum-poisoned possums. Caged possums were fed a lethal dose of brodifacoum in cereal baits then either bled and killed 4, 8, 12, 16 or 20 days later to establish the effects on blood-clotting, or observed for behavioural changes until death. Blood-clotting time was prolonged 8 days after possums first began ingesting brodifacoum and time to death was 20.7 ± 1.7 days (mean ± s.e.m.). Clinical signs of poisoning, including changed appearance, pale noses and external bleeding, appeared from 14 days after initial poisoning (7 days before death). Possums gradually became inactive and lethargic, typically crouching and lying in abnormal postures for 6 days before death. Feed intake reduced concurrently, resulting in significant loss of body weight of 5.9 ± 2.1%. All possums had widespread, usually severe, haemorrhaging. Internal haemorrhages first appeared in all possums 8 days after initial ingestion. These haemorrhages, and consequent blood loss, may cause distress, pain, weakness or sickness, and this is supported by evidence from humans and other animals. Reduced feed intake, inactivity, lethargy and the display of abnormal postures suggest that possums do experience distress for at least 6 days before death.
Beyond population regulation and limitation
Authors: Krebs Charles J.
Published: March 2003

The study of population dynamics addresses three questions that are not always
separated in discussions with empirical data. Two questions address population
regulation. What stabilises population density is the
first question, and, in spite of much theory, little progress has been made in
answering this question empirically. The assumption of an equilibrium density
is impossible to test and direct experimental tests to answer this question
are rare. What prevents population growth is a second
question, and is the classic question of population regulation. To answer this
question requires an increasing population, and, with adequate experimental
manipulations, the density dependent factors preventing increase can be
identified. Surprisingly, answering this question has provided little
assistance in solving practical problems in population dynamics, possibly
because most populations are rarely in the state of growth and show a limited
range of densities.
What limits population density in good and poor habitats
is a third question, which addresses population limitation rather than
regulation, and has been the most useful question for empirical ecologists to
ask. Population limitation admits of little theory and no elegant models, and
highlights the gap between theory and practice in much of ecology. Defining
the question clearly and adopting an experimental approach with clear
alternative hypotheses will be essential to avoiding the controversies of the
past while building useful generalisations for the practical problems of
population management.
Evaluation of bait stations for broadacre control of rabbits
Authors: Twigg Laurie E. , Lowe Tim J. , Martin Gary R.
Published: March 2003

The efficacy of bait stations (200-L drum cut in half longitudinally) for the broadacre control of rabbits was compared with that obtained with standard trail-baiting procedures in the southern agricultural region of Western Australia. Bait stations were tested with and without the provision of pre-feed. The bait used was 1.0% 1080 One-shot oats, and corresponding experimental control sites were treated with unpoisoned oats. On the basis of spotlight counts before and after baiting, the reduction in rabbit numbers obtained with bait stations in the absence of pre-feed was poor, with a mean reduction of only 27% within 14 days. These reductions did not improve appreciably where sites were monitored for a further 28 days (i.e. 42 days in total). In contrast, the provision of pre-feed for 21 days prior to adding the 1080 bait resulted in a mean reduction in rabbit numbers of 57% within 14 days after the poisoned bait was added. However, the greatest reductions in rabbit numbers were achieved with trail baiting, where, relative to pre-treatment counts, rabbit numbers were reduced by 72% at Day 7 and by 84% at Day 14. The oats used to manufacture the 1080 One-shot product are subjected to gamma-sterilisation to prevent the germination of the oats, and any associated seeds of weed species. When offered a choice (matched sets), there was no difference in the amount of non-toxic gamma-sterilised oats and unsterilised oats consumed by free-ranging wild rabbits. On the basis of the costs incurred during the trials, trail baiting was by far the cheapest option for the broadacre control of rabbits. However, the cost of using bait stations would be discounted to some degree once these stations are able to be reused. The cost of trail baiting to protect a 15-ha 'border' of crop was $157 and $113 for three and two parallel trails (6 kg km–1 trail–1), respectively.
The population ecology of the squirrel glider (Petaurus norfolcensis) within a network of remnant linear habitats
Authors: Ree Rodney van der
Published: March 2003

The geographic range of the squirrel glider (Petaurus norfolcensis) in south-eastern Australia largely corresponds with fertile soils highly suited for agriculture. As a consequence of extensive clearing for agriculture, the conservation of P. norfolcensis in south-eastern Australia is now reliant on a mosaic of many fragmented and isolated patches of woodland and forest. In this study, I investigated the population dynamics of P. norfolcensis in an agricultural landscape where most remnant woodland occurs as linear strips along roadsides, unused road reserves and watercourses. A total of 251 gliders were trapped 1343 times within the linear habitats between December 1996 and November 1998. Gliders were resident within the linear strips at 0.95–1.54 individuals ha–1, a density equal to, or greater than, that recorded elsewhere for the species in continuous forest. All adult females were reproductively active and the mean natality rate was 1.9 young per adult female per year. Overall, the population age-structure appeared to be stable. While currently supporting a stable, high-density population, the long-term viability of these remnants as habitat is not assured because roadside reserves are narrow, easily fragmented and subjected to a host of deleterious processes causing ongoing habitat loss and degradation.
Reproduction of the purple-necked rock-wallaby, Petrogale purpureicollis Le Souef (Marsupialia : Macropodidae) in captivity, with age estimation and development of the pouch young
Authors: Johnson Peter M. , Delean Steven
Published: March 2003

Reproduction of the purple-necked rock-wallaby, Petrogale purpureicollis, was studied in captivity. The length of the oestrous cycle was 36–38 days followed by a gestation period of 33–35 days. Birth was usually followed by an oestrus and mating, and a subsequent lactation-controlled embryonic diapause. The interval between loss of pouch young and birth was 30–36 days. Pouch life was 178–197 days and weaning occurred 92–171 days after permanent emergence from the pouch. The youngest age at which sexual maturity was reached was 21.8 months for males and 18 months for females. Linear mixed-effects models were used to describe polynomial growth equations for age determination of pouch young using both head and pes length. The relationship between error in age prediction and each body measurement was also defined. Head measurements provided the most accurate estimates of the age of pouch young.
The fate of dried meat baits laid for fox control: the effects of bait presentation on take by foxes and non-target species, and on caching by foxes
Authors: Thomson P. C. , Kok N. E.
Published: March 2003

Non-toxic, dried meat baits (45 g) containing small radio-transmitters were laid on cleared sandplots in mixed farming and grain-growing areas in Western Australia. Baits were either buried, tethered by wire trace to a hidden peg, or simply laid untethered on the surface. Baits were exposed for 1 night only and new transects were established each day. Data were available on 1521 baits. Red foxes (Vulpes vulpes) visited 23% of plots and took baits from 64% of those visited. Unburied baits (both tethered and untethered) were taken significantly more frequently than the buried baits. Of all baits taken by foxes, 25% were cached. Foxes were more likely to cache buried baits than either tethered or untethered baits. Excluding baits taken to cubs, foxes cached baits 3–380 m (mean 87�m) from their original locations. Some baits were carried to cub dens up to 1.25�km away. The fate of 27�cached baits was monitored for varying periods. Of these baits, 59% were later eaten by foxes, most within 3�days. Non-target species took 3% of the baits on offer. Birds were the most common non-target animals to take baits, and in some cases dropped baits up to 400 m away. In terms of takes relative to visits, most takes by birds were of the untethered baits (88%, cf. 33% for tethered, 17% for buried baits). Compared with other baits, a significantly lower proportion of the untethered baits that were taken by birds was actually eaten. Baits cached by foxes and baits moved by birds represent a potential hazard to farm dogs and vulnerable fauna. Recommendations on bait presentation, distance restrictions, and likely risk to farm dogs and non-target species are discussed.
The distribution and habitat requirements of the great barred frog (Mixophyes fasciolatus)
Authors: Parris Kirsten M.
Published: March 2003

The great barred frog (Mixophyes fasciolatus) is a common, ground-dwelling frog from the forests of eastern Australia, with a wide geographic distribution extending from mid-east Queensland to southern New South Wales. This paper presents a quantitative assessment of the distribution and habitat requirements of M. fasciolatus, using data collected during a stratified survey across its geographic and environmental range. I found M. fasciolatus at 55 of 124 sites, and in all areas of forest surveyed except for Girraween National Park in Queensland and the southern highlands of New South Wales. I detected 42 other species of frogs during the survey, including the introduced cane toad (Bufo marinus). Statistical habitat modelling indicated that in forests within its climatic range, M. fasciolatus was most likely to occur in wetter forests (wet sclerophyll forest and rainforest), in areas with lower precipitation and intermediate temperatures in the warmest (summer) quarter of the year. When present at a site, the number of individuals of M. fasciolatus detected during a survey (a measure of relative abundance) was predicted to decrease with increasing summer precipitation. This frog survey represents one of the largest ever undertaken in Australia, with a study area of 125�000 km2, and 124 survey sites in 21 State Forests and nine National Parks. Field data collected during the study and the resulting habitat models provide a baseline against which future changes in the distribution or abundance of M. fasciolatus may be assessed.
Dispersal and population dynamics of the blue-breasted fairy-wren, Malurus pulcherrimus, in fragmented habitat in the Western Australian wheatbelt
Authors: Brooker L. C. , Brooker M. G.
Published: March 2003

The blue-breasted fairy-wren, Malurus pulcherrimus, is a small, permanently sedentary, socially monogamous, co-operatively breeding, long-lived Australian passerine, whose core distribution is contained within the Western Australian wheatbelt. Little is known of their dispersal capabilities and population dynamics, knowledge of which are urgently needed as their preferred habitat becomes increasingly fragmented and degraded, due to clearing for agriculture.
From 1993 to 1998, we studied a colour-banded population of blue-breasted fairy-wrens living in 13 small, 3 medium-sized and one large habitat remnant in an agricultural landscape at Wyalkatchem. Wrens in small remnants were more likely to disperse between remnants than were those in larger remnants. Females were likely to travel further and were more likely to disperse between remnants than were males. Dispersing females in the largest remnant moved a median straight-line distance of 400 m compared with 3 km for females in the smaller remnants. The furthest recorded movement was 9 km (straight-line distance) or about 14 km by the nearest corridor route. Females living in fragmented habitat may have to travel many times the distances travelled by females in unfragmented habitat.
Demographic modelling shows that, over an average run of seasons, the wrens in the study population will produce sufficient yearlings to fill all breeding vacancies, provided none are lost during dispersal. However, in our study landscape, an estimated 11% of dispersers were lost to the population (i.e. either dispersed outside the study area or died during dispersal). We show that the remnants in the study landscape can be divided into neighbourhoods based on their relative connectivity. About 14% more potential dispersers were lost from the poorly-connected areas than from a core 'well connected' neighbourhood. This difference would be sufficient to cause population decline in a poorly connected neighbourhood. We conclude that, for species with poor dispersal capacity living in fragmented habitat, failure to maintain an adequate corridor network could be one of the most important factors contributing to a species' decline.
Mortality rates of feral ferrets (Mustela furo) in New Zealand
Authors: Caley Peter , McElrea L. M. , Hone Jim
Published: March 2003

Life-table data from feral ferret populations in New Zealand were analysed to estimate their mortality rates, and to test for any additive effect of Mycobacterium bovis infection on observed mortality rates. The observed instantaneous mortality rate was best estimated by modelling mortality as a 2-phase step model with different rates for juveniles (μ1 = 1.45 year–1, 95% C.I. 1.2–1.7 year–1) and adults (μ2 = 0.55 year–1, 95% C.I. 0.4–0.9 year–1). This corresponds to a survival probability of 0.25 during the first year of life, rising to 0.55 year–1 thereafter, and a life expectancy of 0.95 years. At a population level, no additional mortality due to M. bovis infection was observed, suggesting either that the rate of disease-induced mortality was negligible, or that it was compensatory with natural mortality.
The index of relative importance: an alternative approach to reducing bias in descriptive studies of animal diets
Authors: Hart R. K. , Calver M. C. , Dickman C. R.
Published: March 2003

The Index of Relative Importance (IRI) is a composite measure that reduces bias in descriptions of animal dietary data. The two papers introducing the IRI in 1971 had been cited a total of 214 times by the end of 2001 and proposed as a standard methodology. However, 180 of these citations concerned the description of the diets of fish, indicating that the IRI is not well known outside fisheries biology. This illustrates how the interests of researchers in a narrow range of taxa may restrict the application of a useful technique to particular groups of animals. Here we apply the IRI to dietary data from one mammal species, two bird species and two species of geckoes to illustrate its applicability to a wide range of taxa. We believe the approach should be considered seriously by terrestrial ecologists concerned about the biases inherent in single-index approaches to describing animal diets.