Spatiotemporal dynamics of habitat use by koalas: the checkerboard model

Patch quality and habitat fragmentation shape the foraging patterns of a specialist folivore

Research on use of foraging patches has focused on why herbivores visit or quit patches, yet little is known about visits to patches over time. Food quality, as reflected by higher nutritional quality and lower plant defenses, and physical patch characteristics, which offer protection from predators and weather, affect patch use and hence should influence their revisitation. Due to the potentially high costs of moving between patches, fragmented habitats are predicted to complicate foraging decisions of many animals. We aimed to determine how food quality, shelter availability and habitat fragmentation influence tree reuse by a specialist folivore, the koala, in a fragmented agricultural landscape. We GPS-tracked 23 koalas in northern New South Wales, Australia and collated number of revisits, average residence time, and average time-to-return to each tree. We measured tree characteristics including food quality (foliar nitrogen and toxic formylated phloroglucinol compounds, FPCs concentrations), tree size, and tree connectedness. We also modeled the costs of locomotion between trees. Koalas re-visited isolated trees with high leaf nitrogen disproportionately often. They spent longer time in trees with high leaf nitrogen, and in large trees used for shelter. They took longer to return to trees with low leaf nitrogen. Tree connectivity reduced travel costs between patches, being either individual or groups of trees. FPC levels had no detectable effect on patch revisitation. We conclude that food quality and shelter drive koala tree re-visits. Scattered, isolated trees with nutrient-rich leaves are valuable resource patches for koalas despite movement costs to reach them.

Memory and Conformity, but Not Competition, Explain Spatial Partitioning Between Two Neighboring Fruit Bat Colonies

Spatial partitioning between neighboring colonies is considered a widespread phenomenon in colonial species, reported mainly in marine birds. Partitioning is suspected to emerge due to various processes, such as competition, diet specialization, memory, information transfer, or even “foraging cultures.” Yet, empirical evidence from other taxa, and studies that tease apart the relative contribution of the processes underlying partitioning, remain scarce, mostly due to insufficiently detailed movement data. Here, we used high-resolution movement tracks (at 0.125 Hz) of 107 individuals belonging to two neighboring colonies of the Egyptian fruit bat (Rousettus aegyptiacus), a highly gregarious central-place forager, using the ATLAS reverse-GPS system in the Hula Valley, Israel. Based on comparisons between agent-based mechanistic models and observed spatial partitioning patterns, we found high levels of partitioning of both area and tree resources (<11% overlap) that were stable across different fruiting seasons. Importantly, partitioning could not have emerged if the bats’ movement was only limited by food availability and travel distances, as most commonly hypothesized. Rather than density-dependent or between-colony competition, memory, and, to a lesser extent, conformity in tree-use explain how partitioning develops. Elucidating the mechanisms that shape spatial partitioning among neighboring colonies in the wild under variable resource conditions is important for understanding the ecology and evolution of inter-group coexistence, space use patterns and sociality.

Estimating koala density from incidental koala sightings in South-East Queensland, Australia (1997-2013), using a self-exciting spatio-temporal point process model

The koala, Phascolarctos cinereus, is an iconic Australian wildlife species facing a rapid decline in South-East Queensland (SEQLD). For conservation planning, the ability to estimate the size of koala populations is crucial. Systematic surveys are the most common approach to estimate koala populations but because of their cost they are often restricted to small geographic areas and are conducted infrequently. Public interest and participation in the collection of koala sighting data is increasing in popularity, but such data are generally not used for population estimation. We modeled monthly sightings of koalas reported by members of the public from 1997 to 2013 in SEQLD by developing a self-exciting spatio-temporal point process model. This allowed us to account for characteristics that are associated with koala presence (which vary over both space and time) while accounting for detection bias in the koala sighting process and addressing spatial clustering of observations. The density of koalas varied spatially due to the heterogeneous nature of koala habitat in SEQLD, with a mean density of 0.0019 koalas per km2 over the study period. The percentage of land areas with very low densities (0-0.0005 koalas per km2) remained similar throughout the study period representing, on average, 66% of the total study area. The approach described in this paper provides a useful starting point to allow greater use to be made of incidental koala sighting data. We propose that the model presented here could be used to combine systematic koala survey data (which is spatially restricted, but more precise) with koala sighting data (which is incidental and often biased by nature, but often collected over large geographical areas). Our approach could also be adopted for modeling the density of other wildlife species where data is collected in the same manner.

Application of low-power wide-area network GPS to koala monitoring

We evaluated long range antennae and associated solar-powered global positioning system (GPS) ear tags designed for use with domestic cattle, as a novel system for monitoring ranging behaviour of the koala (Phascolarctos cinereus). The mean location error of our GPS tags was 33.9 m (s.e. = 0.46). The tags were relatively light (30 g), reported eight locations per day when attached to koala radio-collars and had an operating life that exceeded our study period (8 months). Deployed as a stand-alone, solar powered, remote system, this technology can provide a viable option for wildlife tracking projects.

Comparison of three methods of estimating the population size of an arboreal mammal in a fragmented rural landscape

Abstract Context Precise and accurate estimates of animal numbers are often essential for population and epidemiological models, as well as for guidance for population management and conservation. This is particularly true for threatened species in landscapes facing multiple threats. Estimates can be derived by different methods, but the question remains as to whether these estimates are comparable. Aims We compared three methods to estimate population numbers, namely, distance sampling, mark–recapture analysis, and home-range overlap analysis, for a population of the iconic threatened species, the koala (Phascolarctos cinereus). This population occupies a heavily fragmented forest and woodland habitat on the Liverpool Plains, north-western New South Wales, Australia, on a mosaic of agricultural and mining lands. Key resultsAll three methods produced similar estimates, with overlapping confidence intervals. Distance sampling required less expertise and time and had less impact on animals, but also had less precision; however, future estimates using the method could be improved by increasing both the number and expertise of the observers. ConclusionsWhen less intrusive methods are preferred, or fewer specialised practitioners are available, we recommend distance sampling to obtain reliable estimates of koala numbers. Although its precision is lower with a low number of sightings, it does produce estimates of numbers similar to those from the other methods. However, combining multiple methods can be useful when other material (genetic, health and demographic) is also needed, or when decisions based on estimates are for high-profile threatened species requiring greater confidence. We recommend that all estimates of population numbers, and their precision or variation, be recorded and reported so that future studies can use them as prior information, increasing the precision of future surveys through Bayesian analyses.

Koala tree selection in a mixed-tenure landscape and post-fire implications

Abstract ContextThe more frequent and intense bushfires predicted under climate change are likely to heavily impact koalas living inside protected areas and intact forests, which makes koala habitat in asset protection zones more important. Understanding how koalas use different habitats in a mixed-tenure landscape can inform effective conservation management. AimsThe aims of this study were to determine (1) the species and size of trees used by koalas, (2) whether choice of daytime trees was affected by available proportions of tree species and sizes in koala home ranges, and (3) whether developed land was used as frequently as native forest. MethodsTree use by koalas was determined by radio-tracking 10 koalas for an average of 12 months and recording the species and diameter of trees they occupied. To compare the proportions of tree species used by koalas with those available, tree availability was measured using random quadrats in the home ranges of five koalas that used forested areas extensively. The habitats used by 10 koalas were classified as native forest or developed land to investigate the importance of human-modified areas. Key resultsEucalyptus punctata was a preferred tree species, but each individual used four to nine species. Tree species were not chosen solely on the basis of available proportions; some species were selected preferentially. Half of the koalas used more developed land than native forest. Koalas preferentially used trees with larger diameters than the mean of available trees, and selected larger trees in developed areas than in native forest and when re-using trees. ConclusionsDespite the higher availability of trees in protected native forest at the site, 70% of the koalas used developed land in and around asset protection zones. Koalas whose home ranges were geographically close, but had different soil types and vegetation communities, were able to utilise different tree species. ImplicationsKoalas would benefit from protection of remnant native forests containing preferred trees on shale cap soil and conservation of native vegetation corridors along fence lines and in paddocks in developed areas because they are valuable resources and connect patchy landscapes. Protecting koalas on developed land improves their likelihood of surviving bushfires, allowing recolonisation of surrounding protected areas.

Inbreeding and disease avoidance in a free-ranging koala population

Habitat destruction and fragmentation are increasing globally, forcing surviving species into small, isolated populations. Isolated populations typically experience heightened inbreeding risk and associated inbreeding depression and population decline; although individuals in these populations may mitigate these risks through inbreeding avoidance strategies. For koalas, as dietary specialists already under threat in the northern parts of their range, increased habitat fragmentation and associated inbreeding costs are of great conservation concern. Koalas are known to display passive inbreeding avoidance through sex-biased dispersal, although population isolation will reduce dispersal pathways. We tested whether free-ranging koalas display active inbreeding avoidance behaviours. We used VHF tracking data, parentage reconstruction, and veterinary examination results to test whether free-ranging female koalas avoid mating with (a) more closely related males; and (b) males infected with sexually transmitted Chlamydia pecorum. We found no evidence that female koalas avoid mating with relatively more related available mates. In fact, as the relatedness of potential mates increases, so did inbreeding events. We also found no evidence that female koalas can avoid mating with males infected with C. pecorum. The absence of active inbreeding avoidance mechanisms in koalas is concerning from a conservation perspective, as small, isolated populations may be at even higher risk of inbreeding depression than expected. At risk koala populations may require urgent conservation interventions to augment gene flow and reduce inbreeding risks. Similarly, if koalas are not avoiding mating with individuals with chlamydial disease, populations may be at higher risk from disease than anticipated, further impacting population viability.

Scattered paddock trees and roadside vegetation can provide important habitat for koalas (Phascolarctos cinereus) in an agricultural landscape

Habitat loss and fragmentation threaten the survival of koalas in Queensland. In rural landscapes, remaining koala habitat is often in the form of scattered paddock trees, patches of vegetation and roadside vegetation. The aims of this study were to (1) quantify the use of these three habitat types; (2) determine whether there is an increased use of scattered trees during the breeding season; and (3) describe the movement characteristics (daily step-length and turning angle) of koalas in different habitat types. To do this, koalas were caught and fitted with global positioning system (GPS) loggers that recorded their daily locations. We found koalas utilised all three habitat types in both breeding and non-breeding seasons, but roadside vegetation and scattered trees were utilised significantly more than expected based on their availability within the landscape. We found no significant difference in step-length or turning angles in scattered trees compared with patches of vegetation. We conclude that scattered trees are a critical element of habitat in this rural landscape. This work provides evidence that retaining or planting scattered trees within the rural landscape would likely complement or possibly enhance the conservation value of rural landscapes for koalas.

A Necropsy Study of Disease and Comorbidity Trends in Morbidity and Mortality in the Koala (Phascolarctos cinereus) in South-East Queensland, Australia

Koalas are an iconic Australian marsupial undergoing precipitous population reduction in South-East Queensland from complex interacting threats. To investigate the causes of death and the interaction of comorbidities with demography in South-East Queensland koalas, a large scale, high-throughput prospective necropsy survey was conducted spanning 2013–2016. During this period, 519 necropsies were conducted in 155 young/subadult koalas, 235 mature, 119 old koalas and 10 of unknown age. Similar numbers of males and females were assessed. Trauma and infectious disease at were the most common single diagnoses. However, comorbidity was frequent, including multicentric infection or infectious disease in combination with trauma or senescence. Female koalas had proportionally more reproductive chlamydiosis compared to males in which the ocular and urinary systems were more commonly affected. Comorbidity and disease were strongly associated with poor body condition, and trauma was associated with good body condition. Animals affected by motor vehicle trauma were often in better body condition than those affected by animal attack, tree fall or other causes of trauma. This study identified a higher frequency of infections and comorbidity then previously reported, confirming the complex nature of interacting threats to the koala population.

Passive acoustics and sound recognition provide new insights on status and resilience of an iconic endangered marsupial (koala Phascolarctos cinereus) to timber harvesting

Retention forestry aims to mitigate impacts of native forestry on biodiversity, but data are limited on its effectiveness for threatened species. We used acoustics to investigate the resilience of a folivorous marsupial, the koala Phascolarctos cinereus, to timber harvesting where a key mitigation practice is landscape exclusion of harvesting. We deployed acoustic recorders at 171 sites to record male bellows (~14,640 hours) for use in occupancy modelling and for comparisons of bellow rate (bellows night^-1). Surveys targeted modelled medium-high quality habitat, with sites stratified by time since logging and logging intensity, including old growth as a reference. After scanning recordings with software to identify koala bellows, we found a high probability of detection (~0.45 per night), but this varied with minimum temperature and recorder type. Naïve occupancy was ~ 64% across a broad range of forests, which was at least five times more than expected based on previous surveys using alternative methods. After accounting for imperfect detection, probability of occupancy was influenced by elevation (-ve), cover of important browse trees (+ve), landscape NDVI (+ve) and extent of recent wildfire (-ve, but minor effect). Elevation was the most influential variable, though the relationship was non-linear and low occupancy was most common at tableland elevations (> 1000 m). Neither occupancy nor bellow rate were influenced by timber harvesting intensity, time since harvesting or local landscape extent of harvesting or old growth. Extrapolation of occupancy across modelled habitat indicates that the hinterland forests of north-east NSW support a widespread, though likely low density koala population that is considerably larger than previously estimated. Retention forestry has a significant role to play in mitigating harvesting impacts on biodiversity, including for forest specialists, but localised studies are needed to optimise prescriptions for koalas.

The remarkable vocal anatomy of the koala (Phascolarctos cinereus): insights into low-frequency sound production in a marsupial species

Koalas are characterised by a highly unusual vocal anatomy, with a descended larynx and velar vocal folds, allowing them to produce calls at disproportionately low frequencies. Here we use advanced imaging techniques, histological data, classical macroscopic dissection and behavioural observations to provide the first detailed description and interpretation of male and female koala vocal anatomy. We show that both males and females have an elongated pharynx and soft palate, resulting in a permanently descended larynx. In addition, the hyoid apparatus has a human-like configuration in which paired dorsal, resilient ligaments suspend the hyoid apparatus from the skull, while the ventral parts tightly connect to the descended larynx. We also show that koalas can retract the larynx down into the thoracic inlet, facilitated by a dramatic evolutionary transformation of the ventral neck muscles. First, the usual retractors of the larynx and the hyoid have their origins deep in the thorax. Secondly, three hyoid muscles have lost their connection to the hyoid skeleton. Thirdly, the genioglossus and geniohyoid muscles are greatly increased in length. Finally, the digastric, omohyoid and sternohyoid muscles, connected by a common tendinous intersection, form a guiding channel for the dynamic down-and-up movements of the ventral hyoid parts and the larynx. We suggest that these features evolved to accommodate the low resting position of the larynx and assist in its retraction during call production. We also confirm that the edges of the intra-pharyngeal ostium have specialised to form the novel, extra-laryngeal velar vocal folds, which are much larger than the true intra-laryngeal vocal folds in both sexes, but more developed and specialised for low frequency sound production in males than in females. Our findings illustrate that strong selection pressures on acoustic signalling not only lead to the specialisation of existing vocal organs but can also result in the evolution of novel vocal structures in both sexes.

Fine-scale changes in spatial habitat use by a low-density koala population in an isolated periurban forest remnant

Koala (Phascolarctos cinereus) populations in south-east Queensland are in decline. Although various studies have looked at broad-scale tree preference and habitat quality, there has been little attempt to quantify fine-scale activity shifts from one year to the next or examination of activity at the mesoscale. This study quantified koala activity levels in a 909-ha forest patch at Karawatha Forest Park, in south Brisbane. The Spot Assessment Technique was used to quantify activity and tree selection on 33 long-term monitoring plots in 2009 and 2010. In total, 843 trees were searched and koala pellets were found underneath 34 and 47 trees in 2009 and 2010, respectively. A higher proportion of pellets was found underneath Eucalyptus tindaliae and E. fibrosa and there was weak selection for larger trees. A low occurrence of revisits and a minor shift in activity distribution from 2009 to 2010 indicate that the koala population exists at a low density. Rapid declines in koala populations are occurring in primary habitats. Hence, stable low-density koala populations are important for maintaining genetic diversity and connectivity in fragmented urban landscapes.

Individuals matter: predicting koala road crossing behaviour in south-east Queensland

The ability to predict the frequency with which koalas (Phascolarctos cinereus) cross roads is an important step in developing mitigation strategies aimed at maintaining metapopulation viability for this species. In south-east Queensland, Australia, rapid urban development, including fragmentation and vehicle-related mortality, has contributed to a dramatic decline in local koala populations. Assessment of wildlife crossing structures that mitigates the impact of roads demonstrates these to be beneficial for many species. However, building enough structures to enable animals to move freely across impacted landscapes may be prohibitive in complex urban landscapes. The focus for this study was to consider the role of differing characteristics for species at risk. We examined the frequency of road crossings by individual koalas among six subpopulations in south-east Queensland. We explored the influence of potential predictor variables including: age, sex, and distance from roads. We established that road crossings were limited to a subset of individuals, with only 18 of 51 (~35%) koalas studied ever crossing a road. We found that koalas were disproportionately more likely to cross a road if they had initially been found within a distance of 100 m of that road. Males were more likely to cross roads than females, as were koalas aged less than five years. We suggest that successful wildlife road mitigation can be improved by better understanding the road-crossing behaviour of species such as the koala.

A review of climatic change as a determinant of the viability of koala populations

The koala (Phascolarctos cinereus) occupies a broad range of eastern and southern Australia, extending over tropical coastal, semiarid inland and temperate regions. In many areas koala populations are under threat, in particular from the direct and indirect effects of ongoing habitat destruction due to increased urbanisation and other anthropogenic processes. Climate change presents additional threats to the integrity of koala habitats because many species of food and non-food trees have narrow climate envelopes and are unable to adapt to altered temperatures and rainfall. Climate extremes also produce physiological stresses in koalas that may increase the likelihood of outbreaks of chlamydiosis and other diseases. Climate change–related increases in the relative content of toxic chemicals in leaves are further stresses to the koala after ingestion. In addition, populations that originated from a small number of founder individuals are at potential risk due to their relatively low genetic diversity. Strategies that maintain residual habitat fragments and promote the construction of new refugia are now being formulated. Modelling of the impact of habitat metrics on koala distribution is providing important information that can be used in the rehabilitation of koala refugia. In future these models could be augmented with metrics that describe koala homeostasis to inform local conservation strategies. These considerations are also relevant for the maintenance of other taxa in the wider ecosystem that are also at risk from habitat destruction and climate change.

Do koalas really get the blues? Critique of ‘Aversive behaviour by koalas (Phascolarctos cinereus) during the course of a music festival in northern New South Wales, Australia'

It is imperative that the reported results of scientific studies are based on sound data analyses and unbiased interpretation, especially where they may be used to guide government policy and regulation. A recent paper by Phillips (2016) evaluated the behavioural response of radio-collared koalas to an inaugural large music festival held in 2010 in northern New South Wales. The study concluded that six of seven koalas showed an aversive response. However, we regard the paper as misleading because it contains serious errors in the examination of koala home ranges and in the subsequent assessment of ‘aversive behaviour’ during the music festival. We conclude that Phillips’ paper is based on sufficient data to state that three, not six, of the koalas he studied displayed a short-term behavioural response to the music festival. These koalas temporarily moved outside of their estimated ranges during the festival period (10–80 m). Further, Phillips fails to report crucial ecological data regarding the high level of disease and mortality he recorded, which are presented in their entirety in the author’s prior, unpublished report. For the two deaths that are reported, no mention is made that these koalas had pre-existing disease. Rather, the author raises the possibility that the mortalities may have been related to festival-induced stress. The omission of such key data is prejudicial to the interpretation of results. The reported short-term impact of the festival upon some of the study animals is indeed noteworthy; however, it is apparent that the impact has been considerably overstated due to errors of analysis and the omission of critical ecological data. Our critique highlights our concerns by drawing on the author’s unpublished report as well as our own research at the same site over the past five years. Our aim is to ensure that debate over the impact of music festivals on wildlife is based on sound data analyses and unbiased interpretation, to provide guidance to relevant regulators and land managers.

Movement patterns of koalas in remnant forest after fire

The increasing fragmentation of fire-prone forests of Australia has made the remaining populations of koalas (Phascolarctos cinereus) more vulnerable to extinction. We examined the movement patterns of koalas in remnant forest of Port Stephens following a major wildfire. Each koala (n = 55) was monitored regularly by radio-tracking for up to 35 months. The movements of koalas showed a wide variation in patterns, from highly localised movements to long-range dispersal over 20 km. Within the first 12 months, 35% of tracked koalas moved from their release location to new areas where they established home ranges. Daily movement distances of males (mean = 278.3 m) was higher than for females (141.0 m). Monthly displacement ranged from less than 10 m to more than 5 km, and was higher for koalas that subsequently died. Home ranges of males (95% kernel) were significantly larger than those of females (mean for males = 58.9 ± 10.5 ha; mean for females = 25.7 ± 8.6 ha), and this sex difference was also evident for core areas (50% kernel). There were no differences in the movement patterns or home-range sizes of rehabilitated koalas compared with wild koalas. This study has shown that resource depletion from wildfire is short term for koalas because their mobility allows rapid recolonisation of the burnt forest, and they can maintain home ranges within sites regenerating from fire. The reintroduction of rehabilitated koalas into burnt forest may also assist in the recovery of populations in fragmented and isolated habitat.

Chemosensory discrimination of identity and familiarity in koalas

Despite numerous descriptive accounts of scent marking in marsupials, rigorous experimentation is rare, and relatively little evidence exists to show that conspecifics use chemical signals to distinguish between individuals or different social groups. In this study a series of olfactory discrimination tests sought to determine whether: (1) male koala sternal scent gland secretions are individually distinctive; and (2) male koalas can differentiate between the scent of familiar and unfamiliar individuals. In the first experiment a habituation-discrimination trial demonstrated that male koalas discriminate between the scent gland secretions of different unfamiliar individuals. In a second experiment male koalas spent significantly more time investigating scent from unfamiliar males than familiar males, supporting the hypothesis that they differentiate between conspecifics based on their familiarity. Taken together these results suggest that male koalas are able to discriminate the identity and familiarity of conspecifics using chemical cues, and provide a platform for further studies investigating the functional role of olfactory communication in this species.

The Role of Bioacoustic Signals in Koala Sexual Selection: Insights from Seasonal Patterns of Associations Revealed with GPS-Proximity Units

Despite being a charismatic and well-known species, the social system of the koala (Phascolarctos cinereus--the only extant member of the family Phascolarctidae) is poorly known and much of the koala's sociality and mating behaviors remain un-quantified. We evaluated these using proximity logging-GPS enabled tracking collars on wild koalas and discuss their implications for the mating system of this species. The frequency and duration of male-female encounters increased during the breeding season, with male-male encounters quite uncommon, suggesting little direct mating competition. By comparison, female-female interactions were very common across both seasons. Body mass of males was not correlated with their interactions with females during the breeding season, although male size is associated with a variety of acoustic parameters indicating individuality. We hypothesise that vocal advertising reduces the likelihood of male-male encounters in the breeding season while increasing the rate of male-female encounters. We suggest that male mating-season bellows function to reduce physical confrontations with other males allowing them to space themselves apart, while, at the same time, attracting females. We conclude that indirect male-male competition, female mate choice, and possibly female competition, mediate sexual selection in koalas.

Nutritional correlates of koala persistence in a low-density population

It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus) populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts) compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence.

Testing the regional genetic representativeness of captive koala populations in South-East Queensland

Context Captive breeding for release back to the wild is an important component of ex situ conservation but requires genetic diversity that is representative of the wild population and has the ultimate goal of producing ecologically sustainable and resilient populations. However, defining and testing for representativeness of captive populations is difficult. Koalas (Phascolarctos cinereus) are bred for educational and tourism purposes in zoos and wildlife parks in South-East Queensland, but there are drastic declines evident in some wild koala populations in this region. Aim We compared genetic diversity at microsatellite loci and mitochondrial DNA in two captive koala populations with that of the local, wild koalas of South-East Queensland, determining the degree to which genetic diversity of neutral loci had been preserved and was represented in the captive populations. Key results The expected heterozygosity and the allelic richness was significantly greater in one captive colony than one wild South-East Queensland population. There was low but significant differentiation of the captive from wild populations using FST, with greater differentiation described by Jost’s Dest. In contrast, a newly introduced Kullback–Leibler divergence measure, which assesses similarity of allele frequencies, showed no significant divergence of colony and wild populations. The captive koalas lacked many of the mitochondrial haplotypes identified from South-East Queensland koalas and possessed seven other haplotypes. Conclusions Captive colonies of koalas have maintained levels of overall neutral genetic diversity similar to wild populations at microsatellite loci and low but significant differentiation likely resulted from drift and founder effects in small captive colonies or declining wild populations. Mitochondrial DNA suggests that captive founders were from a wider geographic source or that haplotypes have been lost locally. Implications Overall, tested captive koalas maintain sufficient microsatellite diversity to act as an in situ reservoir for neutral genetic diversity of regional populations.

Potential 'ecological traps' of restored landscapes: koalas Phascolarctos cinereus re-occupy a rehabilitated mine site

With progressively increasing anthropogenic habitat disturbances, restoration of impacted landscapes is becoming a critical element of biodiversity conservation. Evaluation of success in restoration ecology rarely includes faunal components, usually only encompassing abiotic and floral components of the ecosystems. Even when fauna is explicitly included, it is usually only species presence/absence criteria that are considered. If restoration is to have a positive outcome, however, populations in restored habitats should exhibit comparable survival and reproductive rates to populations found in undisturbed surroundings. If a species recolonises restored areas but later experiences decreased fitness, restored areas could become ecological sinks or traps. We investigated this possibility in a case study of koalas Phascolarctos cinereus occupying rehabilitated mining areas on North Stradbroke Island, Australia. Our holistic approach compared rehabilitated and undisturbed areas on the basis of their vegetation characteristics, of koalas' body condition, roosting trees, diet, as well as predator index. Koalas using rehabilitated areas appeared to be able to access an adequate supply of roosting and fodder trees, were in good condition and had high reproductive output. We did not find any significant differences in predator density between rehabilitated areas and undisturbed surroundings. The results presented in this study showed there was no evidence that the post-mining rehabilitated areas constitute ecological sinks or traps. However, to reach a definitive conclusion as to whether areas rehabilitated post-mining provide at least equivalent habitat to undisturbed locations, additional research could be undertaken to assess foliar nutrient/water/toxin differences and predation risk in rehabilitated areas compared with undisturbed areas. More generally, the evaluation of whether restoration successfully produces a functional ecological community should include criteria on the fitness of faunal populations reoccupying such sites, so as to ensure functioning ecosystems, rather than ecological sinks or traps, are the outcome.

Movement patterns of an arboreal marsupial at the edge of its range: a case study of the koala

BACKGROUND

Conservation strategies derived from research carried out in one part of the range of a widely distributed species and then uniformly applied over multiple regions risk being ineffective due to regional variations in species-habitat relationships. This is particularly true at the edge of the range where information on animal movements and resource selection is often limited. Here, we investigate home range size, movement patterns and resource selection of koalas Phascolarctos cinereus in the semi-arid and arid landscapes of southwest Queensland, Australia. We placed collars with GPS units on 21 koalas in three biogeographic regions. Home range sizes, resource selection and movement patterns were examined across the three regions.

RESULTS

Habitat selectivity was highest at the more arid, western edge of the koala's range with their occupancy restricted to riparian/drainage line habitats, while the more easterly koalas displayed more variability in habitat use. There was no significant difference between home range sizes of koalas at the western edge of the range compared to the more easterly koalas. Instead, variability in home range size was attributed to spatial variations in habitat quality or the availability of a key resource, with a strong influence of rainfall and the presence of freestanding water on the home range size of koalas. Within a 580 m spatial range, movement patterns of male and female paths showed a tortuous trend, consistent with foraging behavior. Beyond this spatial range, male paths showed a trend to more linear patterns, representing a transition of movement behavior from foraging to breeding and dispersal.

CONCLUSIONS

The difference in home range movement patterns and resource use among the different koala populations shows that behavior changes with proximity to the arid edge of the koala's range. Changes in home range size and resource use near the range edge highlight the importance of further range-edge studies for informing effective koala conservation and management actions, especially when developing species-specific adaptation responses to climate change.

Free-ranging male koalas use size-related variation in formant frequencies to assess rival males

Although the use of formant frequencies in nonhuman animal vocal communication systems has received considerable recent interest, only a few studies have examined the importance of these acoustic cues to body size during intra-sexual competition between males. Here we used playback experiments to present free-ranging male koalas with re-synthesised bellow vocalisations in which the formants were shifted to simulate either a large or a small adult male. We found that male looking responses did not differ according to the size variant condition played back. In contrast, male koalas produced longer bellows and spent more time bellowing when they were presented with playbacks simulating larger rivals. In addition, males were significantly slower to respond to this class of playback stimuli than they were to bellows simulating small males. Our results indicate that male koalas invest more effort into their vocal responses when they are presented with bellows that have lower formants indicative of larger rivals, but also show that males are slower to engage in vocal exchanges with larger males that represent more dangerous rivals. By demonstrating that male koalas use formants to assess rivals during the breeding season we have provided evidence that male-male competition constitutes an important selection pressure for broadcasting and attending to size-related formant information in this species. Further empirical studies should investigate the extent to which the use of formants during intra-sexual competition is widespread throughout mammals.

Reliable genotyping of the koala (Phascolarctos cinereus) using DNA isolated from a single faecal pellet

The koala, an Australian icon, has been added to the threatened species list. Rationale for the listing includes proposed declines in population size, threats to populations (e.g. disease) and loss and fragmentation of habitat. There is now an urgent need to obtain accurate data to assess the status of koala populations in Australia, to ensure the long-term viability of this species. Advances in genetic techniques have enabled DNA analysis to study and inform the management of wild populations; however, sampling of individual koalas is difficult in tall, often remote, eucalypt forest. The collection of faecal pellets (scats) from the forest floor presents an opportunistic sampling strategy, where DNA can be collected without capturing or even sighting an individual. Obtaining DNA via noninvasive sampling can be used to rapidly sample a large proportion of a population; however, DNA from noninvasively collected samples is often degraded. Factors influencing DNA quality and quantity include environmental exposure, diet and methods of sample collection, storage and DNA isolation. Reduced DNA quality and quantity can introduce genotyping errors and provide inaccurate DNA profiles, reducing confidence in the ability of such data to inform management/conservation strategies. Here, we present a protocol that produces a reliable individual koala genotype from a single faecal pellet and highlight the importance of optimizing DNA isolation and analysis for the species of interest. This method could readily be adapted for genetic studies of mammals other than koalas, particularly those whose diet contains high proportions of volatile materials that are likely to induce DNA damage.

Koala habitat use and population density: using field data to test the assumptions of ecological models

In principle, conservation planning relies on long-term data; in reality, conservation decisions are apt to be based upon limited data and short-range goals. For the koala (Phascolarctos cinereus), frequently reliance is made on the assumption that indirect signs can be used to indicate behavioural preferences, such as diet choice. We examined the relationship between the use of trees by koalas and the presence of scats beneath those trees. Tree use was associated with scat presence on 49% of occasions when koalas were radio-tracked in both central Queensland (n = 10 koalas) and south-east Queensland (n = 5 koalas), increasing to 77% of occasions when trees were rechecked the following day. Koala densities were correlated with scat abundance at sites with koala density between ~0.2 and 0.6 koalas per hectare. Our results confirm that scat searches are imprecise indicators of tree use by koalas, but demonstrate that these searches can be used, with caveats, to estimate koala population densities. We discuss how errors in estimating or applying predictive model parameters can bias estimates of occupancy and show how a failure to validate adequately the assumptions used in modelling and mapping can undermine the power of the products to direct rational conservation and management efforts.

Continuous monitoring of feeding by koalas highlights diurnal differences in tree preferences

Context It is difficult to measure feeding rates for most wild nocturnal mammalian herbivores. Thus, although koalas are a popular species to study, we have a poor understanding of their activity patterns and feeding ecology. Researchers often assume that the trees that koalas occupy during the day indicate feeding preferences, but they may better reflect preferred resting sites. Aims We recorded the activities of koalas, with an emphasis on their feeding, particularly when they fed, the trees that they fed from, the number of meals they consumed and the variability in these measurements. Methods We continuously monitored eight koalas by audio- and radio-telemetry for 14 consecutive 24-h periods each. We followed two koalas at a time and recorded the trees they visited, when, where and how long they fed, and the size and nutritional composition of the trees in the landscape. Key results Individual koalas varied in how many trees they visited, how many meals they ate and how long they spent feeding during each 24-h period. They preferred Eucalyptus globulus trees during the day, but fed mainly at night, with a preference for E. viminalis. The trees that koalas visited during the day were larger than those that they visited at night. Conclusions The trees that koalas occupied during the day were poor indicators of their diet preferences, whereas the daily feeding activities of individual koalas varied widely. Implications Predicting a koala’s diet from the trees it occupies during the day is fraught with error. Although the trees that koalas rest in are important in the species ecology for reasons other than feeding, we should refrain from using them to predict an animal’s diet. Because feeding activity is difficult to measure, it is probably best done indirectly by analysing leaf-cuticle fragments or waxes in faeces. The substantial day-to-day variation in koala activities also indicates that behavioural and physiological studies of koalas require long monitoring periods – a week or longer.

Genetic diversity in natural and introduced island populations of koalas in Queensland

Island populations of animals are expected to show reduced genetic variation and increased incidence of inbreeding because of founder effects and the susceptibility of small populations to the effects of genetic drift. Koalas (Phascolarctos cinereus) occur naturally in a patchy distribution across much of the eastern Australian mainland and on a small number of islands near the Australian coast. We compared the genetic diversity of the naturally occurring population of koalas on North Stradbroke Island in south-east Queensland with other island populations including the introduced group on St Bees Island in central Queensland. The population on St Bees Island shows higher diversity (allelic richness 4.1, He = 0.67) than the North Stradbroke Island population (allelic richness 3.2, He = 0.55). Koalas on Brampton, Newry and Rabbit Islands possessed microsatellite alleles that were not identified from St Bees Island koalas, indicating that it is most unlikely that these populations were established by a sole secondary introduction from St Bees Island. Mitochondrial haplotypes on the central Queensland islands were more similar to a haplotype found at Springsure in central Queensland and the inland clades in south-east Queensland, rather than the coastal clade in south-east Queensland.

Perception of male caller identity in Koalas (Phascolarctos cinereus): acoustic analysis and playback experiments

The ability to signal individual identity using vocal signals and distinguish between conspecifics based on vocal cues is important in several mammal species. Furthermore, it can be important for receivers to differentiate between callers in reproductive contexts. In this study, we used acoustic analyses to determine whether male koala bellows are individually distinctive and to investigate the relative importance of different acoustic features for coding individuality. We then used a habituation-discrimination paradigm to investigate whether koalas discriminate between the bellow vocalisations of different male callers. Our results show that male koala bellows are highly individualized, and indicate that cues related to vocal tract filtering contribute the most to vocal identity. In addition, we found that male and female koalas habituated to the bellows of a specific male showed a significant dishabituation when they were presented with bellows from a novel male. The significant reduction in behavioural response to a final rehabituation playback shows this was not a chance rebound in response levels. Our findings indicate that male koala bellows are highly individually distinctive and that the identity of male callers is functionally relevant to male and female koalas during the breeding season. We go on to discuss the biological relevance of signalling identity in this species' sexual communication and the potential practical implications of our findings for acoustic monitoring of male population levels.

Age and seasonal changes in the semiochemicals of the sternal gland secretions of male koalas (Phascolarctos cinereus)

Male koalas communicate with conspecifics using scent markings from their sternal scent gland. We examined age and seasonal changes in the profile of organic compounds produced by koala sternal glands. Scent exudates from 12 male koalas were collected over a one-year period and analysed by direct-injection gas chromatography–mass spectrometry (GC–MS) of the methanol extract. Carboxylic acids, aldehydes, ketones, and alcohols were found to dominate the scent mixture. Thirty-seven compounds were identified by comparison of their spectra with those in the Wiley 138K library. The identity, complexity and relative concentrations of these compounds were found to vary both seasonally and by age of the individuals, with the most odorous and complex mixtures occurring during the mating season. We suggest that seasonal and age differences in the complexity of the chemical composition of the koala scent gland exudate provides evidence that olfactory communication probably has important ramifications for male reproductive success in the wild.