Warmer ambient temperatures reduce protein intake by a mammalian folivore

The interplay between ambient temperature and nutrition in wild herbivores is frequently overlooked, despite the fundamental importance of food. We tested whether different ambient temperatures (10°C, 18°C and 26°C) influenced the intake of protein by a marsupial herbivore, the common brushtail possum (Trichosurus vulpecula). At each temperature, possums were offered a choice of two foods containing different amounts of protein (57% versus 8%) for one week. Animals mixed a diet with a lower proportion of protein to non-protein (P : NP, 0.20) when held at 26°C compared to that at both 10°C and 18°C (0.22). Since detoxification of plant secondary metabolites imposes a protein cost on animals, we then studied whether addition of the monoterpene 1,8-cineole to the food changed the effect of ambient temperature (10°C and 26°C) on food choice. Cineole reduced food intake but also removed the effect of temperature on P : NP ratio and instead animals opted for a diet with higher P : NP (0.19 with cineole versus 0.15 without cineole). These experiments show the proportion of P : NP chosen by animals is influenced by ambient temperature and by plant secondary metabolites. Protein is critical for reproductive success in this species and reduced protein intake caused by high ambient temperatures may limit the viability of some populations in the future. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

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.

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.

Body temperature of free-ranging koalas (Phascolarctos cinereus) in south-east Queensland

The distribution of the koala (Phascolarctos cinereus) in Queensland is predicted to contract as a result of climate change, driven by the frequency, intensity and duration of heatwaves and drought. However, little is known about the physiological responses of this species to environmental extremes under field conditions. This study aimed to establish the efficacy of surgically implanted thermal radio transmitters and data loggers to measure the body temperature of free-ranging koalas across a range of environmental conditions and ambient temperatures. Five free-ranging koalas in southeast Queensland were implanted with thermal transmitters and data loggers waxed together as a single package. Body temperatures were recorded for variable periods ranging from 3 to 12 months. Diurnal rhythms in body temperature were detected irrespective of season. The long-term diurnal body temperature peak for all koalas occurred between 16:00 and 17:00 h and body temperature was 36.7-36.9 °C, the long-term nadir occurred between 07:00 and 08:00 h and body temperature was 35.4-35.7 °C. Koala body temperatures as low as 34.2 °C and as high as 39.0 °C were recorded. Thermolability became apparent when ambient temperatures were outside the deduced thermal neutral zone for koalas (14.5-24.5 °C): heat was accumulated during the day and dissipated during the cool of the night. While this study is the first to report on body temperature of free-ranging koalas in their normal behavioural context, further investigations are necessary to determine the physiological boundaries of the thermal niche for this species, in order to better equip models that will more accurately predict the impacts of climate change on koalas.

Quantifying koala locomotion strategies: implications for the evolution of arborealism in marsupials

The morphology and locomotor performance of a species can determine their inherent fitness within a habitat type. Koalas have an unusual morphology for marsupials, with several key adaptations suggested to increase stability in arboreal environments. We quantified the kinematics of their movement over ground and along narrow arboreal trackways to determine the extent to which their locomotion resembled that of primates, occupying similar niches, or basal marsupials from which they evolved. On the ground, the locomotion of koalas resembled a combination of marsupial behaviours and primate-like mechanics. For example, their fastest strides were bounding type gaits with a top speed of 2.78 m s^-1 (mean 1.20 m s^-1), resembling marsupials, while the relatively longer stride length was reflective of primate locomotion. Speed was increased using equal modification of stride length and frequency. On narrow substrates, koalas took longer but slower strides (mean 0.42 m s^-1), adopting diagonally coupled gaits including both lateral and diagonal sequence gaits, the latter being a strategy distinctive among arboreal primates. The use of diagonally coupled gaits in the arboreal environment is likely only possible because of the unique gripping hand morphology of both the fore and hind feet of koalas. These results suggest that during ground locomotion, they use marsupial-like strategies but alternate to primate-like strategies when moving amongst branches, maximising stability in these environments. The locomotion strategies of koalas provide key insights into an independent evolutionary branch for an arboreal specialist, highlighting how locomotor strategies can convergently evolve between distant lineages.

Using virtual reality and thermal imagery to improve statistical modelling of vulnerable and protected species

Biodiversity loss and sparse observational data mean that critical conservation decisions may be based on little to no information. Emerging technologies, such as airborne thermal imaging and virtual reality, may facilitate species monitoring and improve predictions of species distribution. Here we combined these two technologies to predict the distribution of koalas, specialized arboreal foliovores facing population declines in many parts of eastern Australia. For a study area in southeast Australia, we complemented ground-survey records with presence and absence observations from thermal-imagery obtained using Remotely-Piloted Aircraft Systems. These field observations were further complemented with information elicited from koala experts, who were immersed in 360-degree images of the study area. The experts were asked to state the probability of habitat suitability and koala presence at the sites they viewed and to assign each probability a confidence rating. We fit logistic regression models to the ground survey data and the ground plus thermal-imagery survey data and a Beta regression model to the expert elicitation data. We then combined parameter estimates from the expert-elicitation model with those from each of the survey models to predict koala presence and absence in the study area. The model that combined the ground, thermal-imagery and expert-elicitation data substantially reduced the uncertainty around parameter estimates and increased the accuracy of classifications (koala presence vs absence), relative to the model based on ground-survey data alone. Our findings suggest that data elicited from experts using virtual reality technology can be combined with data from other emerging technologies, such as airborne thermal-imagery, using traditional statistical models, to increase the information available for species distribution modelling and the conservation of vulnerable and protected species.

Needing a drink: Rainfall and temperature drive the use of free water by a threatened arboreal folivore

Arboreal folivores are particularly vulnerable to the impacts of extreme climate change-driven heatwaves and droughts as they rely on leaf moisture to maintain hydration. During these increasingly frequent and intense weather events, leaf water content may not be enough to meet their moisture requirements, potentially leading to large-scale mortality due to dehydration. Water supplementation could be critical for the conservation of these animals. We tested artificial water stations for a threatened arboreal folivore, the koala (Phascolarctos cinereus), as a potential mitigation measure during hot and dry weather in New South Wales, Australia. We provided ground and tree drinkers to koalas and investigated changes in use with season, environmental conditions and foliar moisture. Our study provides first evidence of the regular use of free water by koalas. Koalas used supplemented water extensively throughout the year, even during cooler months. Time spent drinking varied with season and depended on days since last rain and temperature. The more days without rain, the more time koalas spent drinking. When temperature was high, visits to water stations were more frequent, indicating that in hot weather koalas need regular access to free water. Our results suggest that future changes in rainfall regimes and temperature in Australia have the potential to critically affect koala populations. Our conclusions can be applied to many other arboreal folivorous mammals worldwide which rely on leaves for their nutritional and water requirements. Artificial water stations may facilitate the resilience of vulnerable arboreal folivores during heat and drought events and may help mitigate the effects of climate change.

Seasonal variation in occurrence of oxalate nephrosis in South Australian koalas (Phascolarctos cinereus)

Many koalas (Phascolarctos cinereus) in the Mount Lofty Ranges, South Australia, are affected by oxalate nephrosis, in which renal calcium oxalate deposition occurs. In other species, suboptimal water intake increases the risk of urinary calcium oxalate crystal formation. Koalas principally rely on eucalypt leaf moisture content to maintain hydration but the Mount Lofty Ranges region has hot, dry summers. This study investigates the association between temperature, rainfall and eucalypt leaf moisture and the occurrence of oxalate nephrosis in this population of koalas. Koalas from the Mount Lofty Ranges population that had died or were euthanased between 2008 and 2016 were necropsied and oxalate nephrosis was determined by histopathology (n=50). Leaf moisture content of Mount Lofty eucalypts was determined seasonally. It was found that increased numbers of koalas with oxalate nephrosis died in the months following high mean maximal temperature and in the months following low rainfall. Eucalypt leaf moisture content was not significantly associated with koala deaths. These findings suggest that hot and dry summer/autumn periods contribute to an increased incidence of koala deaths due to oxalate nephrosis. This is probably due to the effects of evaporative water loss and/or lack of access to supplementary drinking water at this time.

Effects of climate on dental mesowear of extant koalas and two broadly distributed kangaroos throughout their geographic range

Dental mesowear analysis can classify the diets of extant herbivores into general categories such as grazers, mixed-feeders, and browsers by using the gross wear patterns found on individual teeth. This wear presumably results from both abrasion (food-on-tooth wear) and attrition (tooth-on-tooth wear) of individual teeth. Mesowear analyses on extinct ungulates have helped generate hypotheses regarding the dietary ecology of mammals across space and time, and recent developments have expanded the use of dental mesowear analysis to herbivorous marsupial taxa including kangaroos, wombats, possums, koalas, and relatives. However, the diet of some of the most ubiquitous kangaroos (e.g., Macropus giganteus) along with numerous other species cannot be successfully classified by dental mesowear analysis. Further, it is not well understood whether climate variables (including precipitation, relative humidity, and temperature) are correlated with dental mesowear variables including various measures of shape and relief. Here, we examine the relationship between dental mesowear variables (including traditional methods scoring the sharpest cusp and a new potential assessment of multiple cusps) and climate variables in the grazers/mixed feeders Macropus giganteus and Macropus fuliginosus, and the obligate browser Phascolarctos cinereus. We find that dental mesowear of mandibular teeth is capable of differentiating the dietary habits of koalas and the kangaroo species. Furthermore, both Macropus giganteus and Phascolarctos cinereus exhibit mesowear correlated with mean minimum temperature, while Macropus fuliginosus dental mesowear is unaffected by temperature, despite significant differences in mean minimum and mean maximum temperature across their distribution (and in the specimens examined here). Contrary to expectations that individuals from drier regions would have blunter and lower relief teeth, dental mesowear is unrelated to proxies of relative aridity—including mean annual precipitation and relative humidity. Collectively, dental mesowear in these marsupials is related to feeding behavior with increased wear in cooler regions (in Macropus giganteus and Phascolarctos cinereus) potentially related to more or different food resources consumed.

Determinants of blood water δ 18O variation in a population of experimental sheep: implications for paleoclimate reconstruction

Mammalian body, blood and hard tissue oxygen isotope compositions (δ ¹⁸O values) reflect environmental water and food sources, climate, and physiological processes. For this reason, fossil and archaeological hard tissues, which originally formed in equilibrium with body chemistry, are a valuable record of past climate, landscape paleoecology, and animal physiology and behavior. However, the environmental and physiological determinants of blood oxygen isotope composition have not been determined experimentally from large herbivores. This class of fauna is abundant in Cenozoic terrestrial fossil assemblages, and the isotopic composition of large herbivore teeth has been central to a number of climate and ecological reconstructions. Furthermore, existing models predict blood water, or nearly equivalently body water, δ ¹⁸O values based on environmental water sources. These have been evaluated on gross timescales, but have not been employed to track seasonal variation. Here we report how water, food, and physiology determine blood water δ ¹⁸O values in experimental sheep (Ovis aries) subjected to controlled water switches. We find that blood water δ ¹⁸O values rapidly reach steady state with environmental drinking water and reflect transient events including weaning, seasons, and snowstorms. Behavioral and physiological variation within a single genetically homogenous population of herbivores results in significant inter-animal variation in blood water δ ¹⁸O values at single collection times (1 s.d. = 0.1-1.4 ‰, range = 3.5 ‰) and reveals a range of water flux rates (t_1/2 = 2.2-2.9 days) within the population. We find that extant models can predict average observed sheep blood δ ¹⁸O values with striking fidelity, but predict a pattern of seasonal variation exactly opposite of that observed in our population for which water input variation was controlled and the effect of physiology was more directly observed. We introduce to these models an evaporative loss term that is a function of environmental temperatures. The inclusion of this function produces model predictions that mimic the observed seasonal fluctuations and match observations to within 1.0 ‰. These results increase the applicability of available physiological models for paleoseasonality reconstructions from stable isotope measurements in fossil or archaeological enamel, the composition of which is determined in equilibrium with blood values. However, significant blood δ ¹⁸O variation in this experimentally controlled population should promote caution when interpreting isotopic variation in the archaeological and paleontological record.

Stable isotope ecology of the koala (Phascolarctos cinereus)

Australia has undergone significant climate change, both today and in the past. Koalas, due to their restricted diet of predominantly eucalyptus leaves and limited drinking behaviour may serve as model organisms for assessing past climate change via stable isotopes of tooth enamel. Here, we assess whether stable carbon and oxygen isotopes from tooth enamel record known climate variables, including proxies of relative aridity (e.g. mean annual precipitation, mean annual maximum temperature, and relative humidity). The results demonstrate significant negative relationships between oxygen isotope values and both relative humidity and mean annual precipitation, proxies for relative aridity. The best model for predicting enamel oxygen isotope values incorporates mean annual precipitation and modelled oxygen isotope values of local precipitation. These data and the absence of any relationship between modelled oxygen isotope precipitation values, independently, suggest that koalas do not track local precipitation values but instead record relative aridity. The lack of significant relationships between carbon isotopes and climate variables suggests that koalas may instead be tracking the density of forests and/or their location in the canopy. Collectively, these data suggest that koalas are model organisms for assessing relative aridity over time – much like kangaroos.

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.

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.

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.

Seasonal, sex and live weight variations in feed and water consumptions of adult captive African Giant rats (Cricetomys gambianus, Waterhouse-1840) kept individually in cages

Adult African Giant rats (Cricetomys gambianus, Waterhouse) (AGRs) (n = 231) of both sexes (117 bucks, 114 does) were live-trapped in the wild in Zaria, Nigeria. Live weight (LW), daily feed consumption (FC) and water consumption (WC) of the AGRs were measured during the cold-dry (CDS), hot-dry (HDS) and rainy (RS) seasons for 2 years with the aim of determining seasonal, sex and LW variations. Feed consumption was significantly different (p < 0.001) between all the seasons, with the lowest mean value recorded during the HDS, while the highest was obtained during the RS. Water consumption was also lowest (p < 0.001) during the HDS but did not differ significantly (p > 0.05) between the CDS and RS. Both feed and water consumptions were higher (p < 0.01) in the males (bucks) than the females (does) during the CDS and HDS, but the sex difference was not significant (p > 0.05) during the RS. Feed consumption correlated positively (p < 0.0001) with WC and relative humidity, but negatively (p < 0.0001) with LW, ambient temperature and heat index. In conclusion, both feed and water consumptions in AGRs decrease with increased seasonal heat and adult LW and are lower in does than in bucks during the dry seasons (CDS and HDS). Intervention may be indicated during the HDS to improve feed and water consumptions for optimal performance of the AGRs.

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.

High koala mortality associated with low browse moisture in tropical environments

At St Bees Island, central Queensland, during drought conditions from July 2001 to April 2003, 85% of koala deaths occurred when browse moisture fell below 51% fresh weight. Drought-induced mortality (and changing frequencies or intensities of drought due to climate change) may have a considerable effect upon this population.

Koalas on North Stradbroke Island: diet, tree use and reconstructed landscapes

North Stradbroke Island lies 4 km off the coast of Queensland, Australia. It is home to one of the only naturally occurring island populations of koalas and it is mined for mineral sands. We analysed the diet and day use tree selections of koalas and recorded the tree species composition of revegetated and undisturbed landscapes at this location. We used faecal cuticle examination to compare the diet of koalas that used reconstructed landscapes with that of koalas that used undisturbed areas. Reconstructed landscapes that were composed of more than 95% diet and/or roost tree species had evidence of use by koalas. Eucalyptus robusta was the most commonly eaten and utilised species and there was no difference in general diet composition between koalas that used the revegetated landscape and those inhabiting undisturbed areas. Other species that were used for roosting and forage included E. racemosa, E. pilularis, Lophostemon confertus and Melaleuca quinquinerva. We observed individual differences and seasonal variation in the diet composition of radio-tracked koalas. These results suggest either flexibility in the diet choices of koalas, or individual preferences within groups of koalas. Our results also indicate that post-mining landscapes can provide habitat that will be used by koalas, which should encourage further efforts into habitat re-creation for native species.

Behavioural contributions to the regulated intake of plant secondary metabolites in koalas

In a given period of time, herbivores often eat less as dietary plant secondary metabolite (PSM) concentrations increase. This reduction in total food intake is interpreted as a need for the herbivore to regulate PSM ingestion in order to avoid toxication. However, regulation of PSM ingestion involves more than the reduction of total intake; it involves an alteration of meal patterns, through a reduction in the number and/or the size of the meals eaten. Despite this, studies of how herbivores alter their meal patterns when offered varying concentrations of PSMs are rare. We investigated whether koalas adjust the number and/or the size of their meals when offered eucalypt foliage varying naturally in concentrations of formylated phloroglucinol compounds (FPCs), a group of PSMs that have previously been shown to inhibit total food intake. High FPC concentrations caused koalas to eat more slowly, eat shorter meals and eat less per meal, which resulted in a reduced total intake. Because increasing FPC concentrations did not cause koalas to alter the number of meals that they ate, clear individual differences between koalas were observed, where some consistently ate fewer larger meals and others ate many smaller meals. Thus, different feeding strategies may still achieve the same outcome of a regulated intake of PSMs. The changes observed match the meal patterns of other herbivores ingesting PSMs known to stimulate nausea and emetic pathways, supporting the idea that feedback signals from nausea are an important way that koalas avoid toxication when eating eucalypt foliage.

Tree use by koalas (Phascolarctos cinereus) after fire in remnant coastal forest

The aim of this study was to examine the effects of fire on resource use by a population of koalas in remnant coastal forest. Fifty-five koalas were monitored regularly by radio-tracking for up to 35 months. The attributes of each tree in which the koala was sighted were recorded, giving a total of 8390 records. Analyses were undertaken on a range of ecological information. Regeneration of the forest began immediately following the fires and within three months koalas were seen among the epicormic growth. From a total 4631 trees used by koalas, 3247 (70%) were burnt. Observations of koalas feeding included 53% in burnt trees. Koalas changed trees frequently; individual trees were used once only on 3555 occasions (42% of all observations). Of all the trees used, 95% were used by only one collared koala; no trees were used by more than three koalas. Swamp mahogany (Eucalyptus robusta) was the tree species most frequently used by koalas, particularly at night and by breeding females. Koalas preferred trees of larger diameter (>30 cm) and used significantly taller trees during summer. This study has shown that resource depletion from intense wildfire is short-term for koalas because they utilise burnt trees within months of the fire for both food and shelter.

The development of habitat selection by subadult koalas

Dispersal by subadults is the principal source of gene flow between groups of koalas in Queensland, so understanding the behaviour of these immature animals is a priority for understanding the ecology of the species. Recent reports postulate that dispersing young koalas may inherit maternal tree selection, but avoid competing with adults. We compared the tree use and diet of adult female koalas with that of their offspring on St Bees Island, Queensland, using radio-tracking and faecal cuticle analysis, to examine this prediction. Koalas at St Bees Island used both fodder and non-fodder species during daytime, moving into fodder species at night. Koala diets were dominated by Eucalyptus tereticornis with E. platyphylla and Corymbia intermedia also represented. Utilisation of daytime tree species was diverse, but at night koalas were found almost exclusively in those species present in their diet. Use of trees during daytime by natal young and young adult koalas were similar to that of maternal adults, but tree use by intermediate stages (independent and dispersing young) during daytime varied from that of the mothers. This resource separation indicates that if tree utilisation for resting is learned from the mother, young animals are excluded from preferred trees while dispersing.

Energetics of free-ranging mammals, reptiles, and birds

We summarize the recent information on field metabolic rates (FMR) of wild terrestrial vertebrates as determined by the doubly labeled water technique. Allometric (scaling) relationships are calculated for mammals (79 species), reptiles (55 species), and birds (95 species) and for various taxonomic, dietary, and habitat groups within these categories. Exponential equations based on body mass are offered for predicting rates of daily energy expenditure and daily food requirements of free-ranging mammals, reptiles, and birds. Significant scaling differences between various taxa, dietary, and habitat groups (detected by analysis of covariance with P < or = 0.05) include the following: (a) The allometric slope for reptiles (0.889) is greater than that for mammals (0.734), which is greater than that for birds (0.681); (b) the slope for eutherian mammals (0.772) is greater than that for marsupial mammals (0.590); (c) among families of birds, slopes do not differ but elevations (intercepts) do, with passerine and procellariid birds having relatively high FMRs and gallinaceous birds having low FMRs; (d) Scleroglossan lizards have a higher slope (0.949) than do Iguanian lizards (0.793); (e) desert mammals have a higher slope (0.785) than do nondesert mammals; (f) marine birds have relatively high FMRs and desert birds have low FMRs; and (g) carnivorous mammals have a relatively high slope and carnivorous, insectivorous, and nectarivorous birds have relatively higher FMRs than do omnivores and granivores. The difference detected between passerine and nonpasserine birds reported in earlier reviews is not evident in the larger data set analyzed here. When the results are adjusted for phylogenetic effects using independent contrasts analysis, the difference between allometric slopes for marsupials and eutherians is no longer significant and the slope difference between Scleroglossan and Iguanian lizards disappears as well, but other taxonomic differences remain significant. Possible causes of the unexplained variations in FMR that could improve our currently inaccurate FMR prediction capabilities should be evaluated, including many important groups of terrestrial vertebrates that remain under- or unstudied and such factors as reproductive, thermoregulatory, social, and predator-avoidance behavior.