Effects of vegetation, fire and other disturbance factors on small mammal ecology and conservation

The relationship of vegetation and disturbance factors to the distribution, abundance and diversity of small mammals in the eastern Otway region, Victoria were investigated. Antechinus stuartii, Rattus fuscipes and Rattus lutreolus were widely distributed and occurred in the majority of the eleven floristic vegetation groups identified. Antechinus minimus, Antechinus swainsonnii and Pseudomys novaehollandiae had restricted distributions and were recorded in only two or three vegetation groups. New information on the distribution of the rare species P. novaehollandiae, was obtained and two floristically rich vegetation groups that it preferred were identified. Species-rich small mammal communities occurred in vegetation communities with high numbers of sclerophyll plant species and high structural diversity. Maximum food resources were considered to be provided in these communities. Local habitat diversity was also correlated with species-richness. Small mammal abundance was maximum in non-sclerophyllous canmunities, where high plant productivity was considered to be important. For the first time, the presence of the plant pathogen Phytophthora cinnamomi was shown to affect small mammals. It was associated with small mammal communities of low species richness and abundance, Recovery of small mammal populations after wildfire was slow until the fourth year. Mus musculus reached peak abundance from 2-3 years and then declined rapidly. P. novaehollandiae was the only native species that achieved maximum abundance early in the succession. A. stuartii, R. fuscipes and R. lutreolus approached maximum abundance in mid-succession, while Isoodon obesulus was a mid- to late-successional species. A. minimus survived the fire, but did not persist after one year. The pattern of succession was influenced by attributes of species, such as survival after fire, their ability to disperse and reproduce.

Succession of small mammal communities after fire and reintroduction of the swamp antechinus 'Antechinus minimus'

This thesis is involved with changes that have occurred to small mammal populations following a major disturbance in the Anglesea region as a result of the 1983 Ash Wednesday fires. Fire, with its effects on spatial and temporal heterogeneity, was found to be an important factor in the maintenance of vegetation and small mammal community structure and diversity in the region. Successional changes in vegetation and small mammal communities were described by multivariate analyses, using data collected annually from 22 study sites. The use of factor analysis techniques, in reducing the annual capture data content, enabled long-term changes in the structure of mammal communities to be interpreted. The small mammal communities in the coastal heath and forest vegetation in the Anglesea region show evidence of a general resilience, (the degree and speed of recovery), to disturbance. Two phases of successional response to fire by mammal species have been proposed; a ‘re-establishment’ phase which occurs in the initial 5-6 years post-fire and is accompanied by rapid increase in species’ abundance, and a subsequent ‘maintenance’ phase accompanied by relatively minor changes in abundance. Habitat Suitability Indices were produced relating to these phases. Vertical density measures of understorey shrubs and herb layers showed significant relationships with small mammal species abundance at the study sites. Long term studies following major disturbances are needed to distinguish between short term recovery of plant and animal species and long term changes in these species. Studies extending over a number of years enable a better directional view of changes in small mammal communities than can be determined from . observations made over a short period. As a part of the investigation into temporal change, it was proposed to undertake trial reintroductions of the Swamp antechinus, Ant echinus minimus, a marsupial dasyurid species which was trapped in the area prior to the 1983 fire, but rarely subsequently. Other more commonly observed native small mammal species (e.g. Rattus fuscipes,R. lutreolus, Antechinus stuartii, Sminthopsis leucopus) had re-invaded the proposed reintroduction site after this fire. Failure of A. minimus to re-establish may have been due to spatial separation of the pre-fire populations coupled with the extensive area burnt in 1983, A source population of the species was located about 100km to the west and habitat utilization and interspecific and niche relationships between the species making the small mammal community explored. Discriminant analysis revealed some spatial separation of species within a habitat based on structural vegetation factors rather than floristic factors. Temporal separation of species was observed, asA. minimus were more active than Rattus species during daylight periods. There was evidence of micro-habitat selection by species, and structural vegetation factors were most commonly identified in statistical analyses as contributing towards selection by small mammal species. Following a theoretical modelling study three reintroduction trials were carried out near Anglesea during 1992-94. Individuals were subsequently radio tracked, and habitat relationships between the species in the small mammal community investigated. Although successful breeding of A, minimus occurred during the latter two trials, the subsequent fate of offspring was not determined. Invasive techniques required to adequately monitor young animals were considered potentially too damaging. Telemetry studies indicated a preference of A. minimus for short, wet heath vegetation. Structural vegetation factors were identified as being significant in discriminating between capture locations of species. Small scale and inexpensive trial reintroductions have yielded valuable additional data on this species and may be viewed as a useful tool in the conservation of other small native mammals.

Vascular plant and small mammal communities over an elevational gradient

Plant species richness and plant and small mammal beta diversity decline over the elevational gradient in the Otway ranges. These patterns are influenced by climate, habitat and spatial structure. This highlights the need to preserve continuous habitat and understand the influence of climate, to conserve communities in the changing future.

The effect of powerline corridor management on small mammal communities

This thesis investigated the ecological impacts of powerline corridor management on small mammals. The study found that powerline corridors provide habitat for native small mammal species, contrary to common belief that Australian powerline corridors are poor in native species. It is important however, that ecological sensitive management regimes are implemented.

Effects of a fox removal program on small and medium-sized mammal population dynamics within the Anglesea Heathlands, Victoria

This thesis assessed the diet of foxes within the ALCOA lease area of Anglesea to determine which native and introduced species foxes were eating. Results showed that Swamp Wallaby was regularly eaten but many other mammals, birds, insects and reptiles were also consumed. The response of native mammals to seasonal fox removal was also determined.

Sooty owl ecology and recent small mammal decline

This thesis investigated the ecology of the threatened sooty owl, which was used to improve understanding of recent small mammal declines and how a top-order predator adapted to changes in ecosystem condition following European settlement. This knowledge will help improve biodiversity conservation and management of forested ecosystems in south-eastern Australia.

A comparison of the effectiveness of camera trapping and live trapping for sampling terrestrial small-mammal communities

Context. There is an increasing reliance on the use of camera-trap technologies for surveys of medium to large terrestrial mammals. Camera trapping may, however, also have significant applications for broad-scale surveys of small mammals.
Aims. The present study aims to compare results from camera-trapping surveys to those of the more traditional live trapping techniques. Specifically, it aims to test the effectiveness of the techniques for detecting species, and the cost effectiveness of both approaches.
Methods. Surveys were conducted across 36 sites in the Grampians National Park, Victoria, Australia, between April and July 2009. At each site, independent surveys were conducted for small mammals by using a combination of Elliot and cage trapping, then camera trapping. Results for the two different approaches were compared for both their ability to generate small-mammal presence data and their cost effectiveness.
Key results. Camera-trapping surveys of 36 sites in the Grampians National Park compared favourably with those of live trapping surveys. Similar species were detected across the sites, and camera trapping was a considerably more cost effective than live trapping.
Conclusions. Camera-trapping surveys of small terrestrial mammals may provide a new and cost-effective technique for surveying terrestrial small mammals. This is particularly the case when presence data are the main requirement of the survey, with no requirement to capture and tag animals.
Implications. Given the cost-effective nature of camera trapping, there is potential to use this approach to increase the level of replication and spatial coverage of small-mammal surveys. Improving the replication and spatial coverage of studies has the potential to significantly increase the scope of research questions that can be asked, thus providing the potential to improve wildlife management.

Underestimated and severe : small mammal decline from the forests of south-eastern Australia since European settlement, as revealed by a top-order predator

In Australia, numerous small mammal species have suffered extinction or severe declines in distribution and abundance following European settlement. The extent of these declines from forested areas of south-eastern Australia, however, remains poorly understood. In this paper we use sub-fossil deposits of the sooty owl (Tyto tenebricosa tenebricosa) as a tool for understanding the diversity of the small mammal palaeocommunity. These results are compared to the contemporary sooty owl diet from the same geographical region to investigate the degree of small mammal decline following European settlement. Of 28 mammal species detected in sub-fossil deposits and considered prey items of the sooty owl at the time of European settlement, only 10 species were detected in the contemporary sooty owl diet. Numerous small mammal species have not only recently suffered severe declines in distribution and abundance but have also recently undergone niche contraction, as they occupied a greater diversity of regions and habitats at the time of European settlement. For some species our understanding of their true ecological niche and ecological potential is therefore limited. The species that underwent the greatest declines occupied open habitat types or were terrestrial. The severity of decline is also likely to have resulted in severe disruption of ecosystem functions, with wide scale ecosystem consequences. There is an urgent need to improve small mammal conservation, to maintain crucial ecosystem functions performed by small mammals. It is recommended that broad-scale exotic predator control programs are conducted which may also provide suitable conditions for the re-introduction of locally extinct species.

Genetic status of an endemic marine mammal, the Australian fur seal, following historical harvesting

Genetic variation, and the way in which it is partitioned among populations, has implications for a species’ survival and evolutionary potential. Such information is particularly important for the successful conservation and management of species that have experienced past human impacts and potential losses of genetic diversity. Overharvesting of the Australian fur seal Arctocephalus pusillus doriferus in the 18th and 19th centuries resulted in severe population reductions and elimination of an estimated 17 of 26 colonies. Currently, the subspecies is recovering and c. 20 000 pups are produced annually at 13 colony sites, most of which are situated in Bass Strait in south-eastern Australia. Genetic analysis of samples collected from pups captured at nine colonies revealed no difference in allelic diversity or heterozygosity at five microsatellite loci and no differences in haplotype diversity within a 344 bp region of the mitochondrial DNA control region. There was some evidence for isolation by distance but the program STRUCTURE predicted a single cluster of individuals. Gene flow among colonies appears to be substantial at present, indicating that the Australian fur seal is currently a single, panmictic unit.

Habitat fragmentation disrupts the demography of a widespread native mammal

Fragmentation theory predicts that population persistence should be positively correlated with the size of habitat fragments. The patterns of occurrence of many species are consistent with this prediction, but the demographic processes that determine how species respond to fragmentation are poorly understood. In addition, habitat quality may interact with fragment size as an influence on demographic performance. We investigated these predictions for the native bush rat Rattus fuscipes by testing the following hypotheses: 1) population performance (i.e. viability as determined by various demographic parameters) is positively correlated with fragment size; and 2) population performance is positively correlated with habitat quality. Populations of R. fuscipes were censused in two large (>49 ha) and eight small (<2.5 ha) forest fragments in an agricultural region of southeastern Australia. Fragments with high and low quality habitat were included in each size category. Fragment size influenced multiple aspects of population demography; populations in large fragments had higher densities, older age structures, received more potential immigrants, and were more likely to recruit adults than those in small fragments. Reproductive patterns were more predictable in large fragments. Habitat quality per se had less marked effects; adult females were heavier and subadults more prevalent in fragments with high quality habitat. However, high quality habitat enhanced population performance in small fragments more so than in large ones. Despite being widespread in the study area, R. fuscipes populations are profoundly impacted by habitat fragmentation, with population performance declining with fragment size. Studies based on patterns of species occurrence should be interpreted with caution as they may mask critical processes occurring at the population level. For a thorough understanding of the effects of habitat fragmentation, population-level studies are required.

The disappearing mammal fauna of northern Australia : context, cause, and response

This article provides a context to, attempts an explanation for, and proposes a response to the recent demonstration of rapid and severe decline of the native mammal fauna of Kakadu National Park. This decline is consistent with, but might be more accentuated than, declines reported elsewhere in northern Australia; however, such a comparison is constrained by the sparse information base across this region. Disconcertingly, the decline has similarities with the earlier phase of mammal extinctions that occurred elsewhere in Australia. We considered four proximate factors (individually or interactively) that might be driving the observed decline: habitat change, predation (by feral cats), poisoning (by invading cane toads), and novel disease. No single factor readily explains the current decline. The current rapid decline of mammals in Kakadu National Park and northern Australia suggests that the fate of biodiversity globally might be even bleaker than evident in recent reviews, and that the establishment of conservation reserves alone is insufficient to maintain biodiversity. This latter conclusion is not new; but the results reported here further stress the need to manage reserves far more intensively, purposefully, and effectively, and to audit regularly their biodiversity conservation performance.

Electromagnetic field and other physical methods influencing cell growth in mammal cell culture systems

The growth rate of cultured mammalian cells can be influenced by chemical and physical methods such as electromagnetic fields (EMF), light, temperature and plasma. These physical methods have a number of well documented effects on mammalian cells including modification of gene expression, cell cycle, invasion, motility, cell viability, proliferation, apoptosis and mammosphere numbers. A study of the existing literature confirms that the impact of physical method on mammalian cells depends on the cell type, culture environment, exposure time, frequency, wave shape, and amount of dose. The modification of cell proliferation and apoptosis is necessary for cells products, tissue engineering, and therapy. In this article, we reviewed the impact of four physical methods on the growth rate and viability of cells. Plasma is the best method among fours because we can get desired result ranging from increasing cell proliferation to inducing apoptosis depending on the dose.

Managing fire mosaics for small mammal conservation : a landscape perspective

1.Fire is a major driver of ecosystem structure and function worldwide. It is also widely used as a management tool to achieve conservation goals. A common objective is the maintenance of 'fire mosaics' comprising spatially heterogeneous patches of differing fire history. However, it is unclear what properties of fire mosaics most enhance conservation efforts. Here we focus on the spatial and temporal properties of fire-prone landscapes that influence the distribution of small mammals.

2.We surveyed small mammals in 28 landscapes (each 12·6km²) representing a range of fire histories in the Murray Mallee region (104 000km²) of semi-arid Australia. Generalised linear mixed models were used to examine the influence of five landscape properties on the capture rate of individual species and the species richness of native small mammals. We investigated the influence of the proportional extent of fire age-classes, the diversity of fire age-classes, the extent of the dominant vegetation type, rainfall history and biogeographic context.

3.Three of four study species were associated with the spatial extent of fire age-classes. Older vegetation was found to provide important habitat for native small mammals. Overall, however, rainfall history and biogeographic context were dominant influences: for example, the species richness of native mammals was positively associated with above-average rainfall. There was little evidence that the diversity of fire age-classes influenced either the capture rate of individual species or species richness.

4.Synthesis and applications. In fire-prone environments, habitat availability can change markedly over short time-scales. Sufficient habitat at a suitable seral stage within the landscape is a key requirement for species conservation. In mallee ecosystems, the retention of older vegetation is recommended to create more desirable fire mosaics for native small mammals. In addition to such spatial properties of mosaics that are amenable to manipulation, an understanding of how ecological processes affect the biota (such as variation in rainfall-driven productivity) is also essential for informed conservation management.