Energy Requirements and Water Turnover in Free-Living Leadbeater's Possums, Gymnobelideus Leadbeateri (Marsupialia: Petauridae).

Detailed field and modelling studies have been completed at different spatial scales for the endangered arboreal marsupial, Leadbeater's Possum (Gymnobelideus leadbeateri); a species virtually confined to the ash-type eucalypt forests in the Central Highlands of Victoria, south-eastern Australia. These forests are also subject to considerable pressure to produce timber and paper products. The studies of Leadbeater's Possum highlighted the factors influencing the distribution and abundance of the species ranging from broad distribution patterns, the occupancy of habitat patches at the landscape scale, and the use of individual den sites and the quality of trees that provide food within particular stands. These scales correspond to the entire known range of the species, sub-populations within a metapopulation occupying an ensemble of patches at the landscape scale, and colonies occupying den trees in individual stands. Information on the factors influencing the distribution of Leadbeater's Possum at one spatial scale were found to be important for informing processes at another. For example, an understanding of the species‘ habitat requirements informed the spatial distribution of habitat patches at the landscape level which, in turn, gave insights into predicted metapopulation dynamics. Each spatial scale of ecological investigation of Leadbeater's Possum had a corresponding scale of forest management, and they included: virtually the entire ash-type eucalypt resource in the region, the location of large reserves, the design of corridors and retained patches within production forest landscapes, silvicultural practices employed in individual stands, and the retention of individual trees and clusters of trees on logged sites. This range of forest management scales, and the corresponding-scaled array of ecological studies, have particular implications for the conservation of Leadbeater's Possum. The results of investigations to date have revealed that conservation efforts must focus on ash-type eucalypt forests in the Central Highlands of Victoria because populations of Leadbeater's Possum are virtually confined to these areas. Within the broadscale limits of the distribution of the species, the long-term conservation of Leadbeater's Possum will not only be dependent on large reserves, but also intermediate-scale reserves and corridors within wood production areas, as well changed silvicultural practices to better provide suitable habitat on logged sites. While each strategy will make a contribution to the persistence of Leadbeater's Possum, it also has important limitations; an outcome which highlights the need for a multi-scale approach to attempts to conserve the species. Notably, the overaching implications for the design of an array of different conservation strategies for Leadbeater's Possum could not have been derived from any single study at a particular spatial scale. Thus, the case study on Leadbeater's Possum suggests that consideration of factors at a range of scales should be an integral part of management and conservation planning, not only for this species, but for wildlife per se.

An assessment of ectoparasites across highland and lowland populations of Leadbeater's possum (Gymnobelideus leadbeateri): Implications for genetic rescue translocations.

Forest succession and habitat management for Leadbeater's possum in the State of Victoria, Australia

The numbat (Myrmecobius fasciatus) is a diurnal and exclusively termitivorous marsupial. This study examines interrelationships between diet, metabolic rate and water turnover for wild, free-living numbats. The numbats (488+/-20.8 g) remained in mass balance during the study. Their basal metabolic rate (BMR) was 3.6 l CO(2) day(-1), while their field metabolic rate (FMR) was 10.8+/-1.22 l CO(2) day(-1) (269+/-30.5 kJ day(-1)). The ratio FMR/BMR was 3+/-0.3 for numbats. We suggest that the most accurate way to predict the FMR of marsupials is from the regression log FMR=0.852 log BMR+0.767; ( r(2)=0.97). The FMR of the numbat was lower than, but not significantly different from, that of a generalised marsupial, both before (76%) and after (62-69%) correction for the significant effect of phylogeny on FMR. However the numbat's FMR is more comparable with that of other arid-habitat Australia marsupials (98-135%), for which the regression relating mass and FMR is significantly lower than for nonarid-habitat marsupials, independent of phylogeny. The field water turnover rate (FWTR) of free-living numbats (84.1 ml H(2)O day(-1)) was highly correlated with FMR, and was typical (89-98%) of that for an arid-habitat marsupial after phylogenetic correction. The higher than expected water economy index for the numbat (FWTR/FMR=0.3+/-0.03) suggests that either the numbats were drinking during the study, the water content of their diet was high, or the digestibility of their termite diet was low. Habitat and phylogenetic influences on BMR and FMR appear to have pre-adapted the numbat to a low-energy termitivorous niche.

Rates of turnover of water, energy and sodium were measured in free-ranging and enclosed Lacerta viridis and Vipera aspis at a site in Western France in late summer. Rates of CO2 production did not differ significantly between free-ranging Lacerta and those maintained in large outdoor enclosures and averaged 0.371 ± 0.056 mL(g.hr)-1 which was significantly greater (P < 0.05) than the rate of 0.152 ± 0.02 mL(g.hr)-1 recorded for Vipera aspis living in similar outdoor enclosures. Rates of water, but not sodium, turnover were significantly greater in free-ranging than in enclosed Lacerta (12.03 ± 1.21 mL(100g.day)-1 versus 7.46 ± 1.03 mL(100g.day)-1 respectively), suggesting that the free-ranging individuals, which were captured along a canal, had access to a source of free water not linked with their diet. Field Metabolic Rates (FMR) of Lacerta were positively and significantly correlated with the rate of water turnover and analysis of influx and efflux data indicate that this lizard requires on the average approximately 8mL(100g.day)-1 of water to maintain its hydric balance. A similar analysis suggests that this species requires roughly 1meq(kg.day)-1 of sodium for the maintenance of electrolyte balance. Rates of sodium and water turnover were significantly correlated in captive Lacerta, the diet of which was supplemented daily with mealworms and crickets, but the correlation in the case of animals living by the canal was not significant, indicating again that sources of water and sodium intake were independent in these individuals. Rates of water and sodium turnover were low in the vipers maintained in external enclosures and both elements were in negative balance, as would be expected with non-feeding animals. The data reveal a small but significant intake of sodium however, which was not identified. A regression of water intake versus rate of weight loss suggest that Vipera aspis requires an intake of approximately 2.5mL(100g.day)-1 to maintain hydric balance under these conditions. The data reported here for FMR's and rates of water turnover are compared with those for other lizards in the literature and suggest that Lacerta viridis falls mid-way between desert and tropical species studied to date. Further work with temperate-living species should prove of value in delineating the physiological capacities of terrestrial reptiles.

Leadbeater's possums (Gymnobelideus leadbeateri) are a critically endangered marsupial found in a restricted area of cold, wet forest in South‐Eastern Australia. The majority of Leadbeater's possums inhabit highland forest, with one outlying lowland population. In 2012, a breeding program was established for the lowland Leadbeater's possums when this genetically distinct population faced imminent extinction. Successful reproduction by highland Leadbeater's possums in the international zoo‐based population between 1970 and 2010 led to the widespread belief that the species bred readily in captivity. Lowland possums have not bred in the 2012–2021 contemporary captive conservation breeding program. This study reviewed the historic captive‐breeding data and found that of the 84% (162/194) that reached reproductive maturity; 37% of males (n = 30) and 39.5% of females (n = 32) bred, and this success was highly skewed towards a subset of highly fecund individuals (14% of females and 15% of males produced 75% and 80% of all offspring). Although lack of reproductive output in the captive lowland animals could be explained if age at mortality was lower than that of highlands possums, comparison of the longevity of highland and lowland animals had no significant difference. Conservation objectives that specify how captive breeding may support in situ recovery of wild populations are integral to the success of captive programs. A lack of reflective analysis of past husbandry records allowed misconceptions of success and approaches implemented in the management of the breeding program, reducing the benefits for the conservation of this high profile threatened species. This case study provides a lesson for the management of conservation breeding programs and illustrates the importance of well‐defined conservation objectives, integration of in situ and ex situ strategies, and the importance of objective, systematic and timely analysis of available evidence to inform management objectives and improve conservation outcomes in real time.

Details of the energy (food) requirements of domestic herbivores are essential for predicting grazing pressures and subsequent ecological impacts on rangelands. However, these details are lacking for some of the more recently introduced sheep breeds to Australia, such as the Dorper breed sheep, which are principally meat sheep, and it is uncertain how they compare with the traditional Merino, a wool-breed, sheep. We used the doubly labelled water method to compare the field metabolic rate and water turnover rate of Dorpers and Merinos grazing together in a small holding paddock in a typical rangeland environment. We found no significant differences in field metabolic rate (Dorpers 481 ± 125 kJ and Merinos 500 ± 109 kJ kg–0.73 day–1) or water turnover rate (Dorpers 397 ± 57 mL and Merinos 428 ± 50 mL kg–0.8 day–1). As such we conclude that under controlled conditions with limited movement and ready access to feed and water, dry sheep equivalent of 1 is appropriate for Dorpers (that is, one Dorper ewe had a grazing requirement equal to one standard, dry Merino wether). However, we also found that the field metabolic rate for Merinos under these conditions was only around half that measured in published studies for animals ranging freely in a large paddock system. This suggests that more work is needed to fully appreciate the energetic and grazing impacts of Dorpers versus Merinos under more realistic grazing conditions (e.g. large paddock systems) where feed and water are more spread. It also highlights limitations of the current dry sheep equivalent rating system, which has been derived from laboratory measures of sheep metabolic rates.

Managing Leadbeater's possum in the mountain ash forests of Victoria, Australia—Reply

SummaryRoads and other linear infrastructure create treeless gaps that can limit the movement of non‐flying, arboreal animals. These negative effects are particularly strong in dense forests, where even narrow infrastructure corridors represent a significant change in habitat structure. Artificial canopy bridges are an increasingly common approach to mitigating the barrier effect of roads and other linear infrastructure on the movement of arboreal mammals; however, questions remain about the success of various designs for different species. Here we conduct an experimental evaluation of the response of a critically endangered possum, Leadbeater's Possum (Gymnobelideus leadbeateri), to two artificial canopy bridge designs: single‐rope bridges and ladder bridges. We found that both bridges were used by Leadbeater's Possum and five other species of arboreal marsupial to cross narrow, forestry roads. However, Leadbeater's Possums crossed ladder bridges 13 times more often than the single‐rope design (average of 564.5 and 41.75 crossings per design respectively). Radiotelemetry conducted on four Leadbeater's Possums prior to bridge installation detected no road crossings, providing preliminary evidence that the bridges improved cross‐road movement. Ladder bridges appear to be the better design choice for a wider range of arboreal marsupials as they were used more frequently, offer greater stability, and provide better predator avoidance than single‐rope designs.

AimOccurrence records for cryptic species are typically limited or highly uncertain, leaving their distributions poorly resolved and hampering conservation. This can apply to well‐studied species, and increased survey effort and/or novel methods are required to improve distribution data. Here, we paired species distribution modelling (SDM) with decision tools to direct surveys for the critically endangered Leadbeater's possum (Gymnobelideus leadbeateri) outside its current restricted range. We also assessed survey areas for their suitability to host translocations.LocationVictoria, Australia.MethodWe used both recent and historic records (now out of range and spatially uncertain) of Leadbeater's possum to build SDMs using MaxEnt. The SDMs informed an initial multi‐criteria decision analysis (MCDA) that enabled prioritization of 80 survey sites across seven forest patches (13–145 km outside the known range), which we surveyed using camera traps. Site and vegetation data were used in a post‐survey MCDA to rank their potential translocation suitability.ResultsThe SDM predictions were consistent with the species’ ecology, identifying cold areas with high rainfall that had not recently burnt as suitable. The spatial uncertainty of records did not exert a strong influence on either model predictions or the ranking of patches for surveys. Camera trap surveys yielded records of 19 native species, with Leadbeater's possum detected in only one survey patch, 13 km outside of its previously known range. The post‐survey MCDA identified three forest patches as potentially suitable for conservation translocations, and these priorities were not sensitive to the decision criteria used.Main conclusionsThe approach outlined here prioritized survey effort over a large area, resulting in detection of Leadbeater's possum in one new patch. The potential translocation sites identified could present an important risk‐spreading measure for the species given the threat posed by bushfire. Combining SDMs and decision tools can help target surveys and guide subsequent conservation strategies.

In this issue August 2016: Preventive health care of Pony Club horses · Treatment of subclinical Streptococcus equi in Thoroughbreds · Cardiac biomarker concentrations in canine tick paralysis · Lead toxicity diagnosis in two dogs · Feline leprosy syndrome (FLS) in a cat · Skin blistering in a dog exposed to Plumbago auriculata · Postpartum anoestrus in seasonally-calving dairy farms

Risk assessment to determine the probability of persistence of populations has an increasingly important role in the development of conservation and resource use strategies. We used the computer program VORTEX to estimate the viability of populations of Leadbeater's possum, Gymnobelideus leadbeateri, an endangered species of forest‐dependent marsupial inhabiting timber production areas in southeastern Australia. The study simulated population dynamics and genetic variability in metapopulations occupying small numbers of habitat patches of varying size. The impacts of different rates of migration between subpopulations were also examined. Computer simulations with subpopulations of 20 or fewer G. leadbeateri were characterized by very rapid rates of extinction, and most metapopulations typically failed to persist for longer than 50 yr. Increasing either the rate of migration or the number of small subpopulations exacerbated the demographic instability of metapopulations when subpopulations contained <20 individuals and when migration rates were kept within plausible values for dispersal of this species between disjunct habitat patches. This was reflected by lower rates of population growth and depressed probabilities of metapopulation persistence. These effects appeared to be associated with substantial impacts of demographic stochasticity on very small subpopulations together with dispersal of animals into either empty patches or functionally extinct (i.e., single‐sex) subpopulations. There were significant differences between metapopulation dynamics of 40 animals and those comprising 20 or fewer individuals. Increased migration and addition of subpopulations of 40 G. leadbeateri resulted in higher rates of population growth, lower probabilities of extinction, and longer persistence times. Extinctions in these scenarios were also more likely to be reversed through recolonization by dispersing individuals. At the highest rates of migration, subpopulations of 40 G. leadbeateri were essentially panmictic and behaved genetically as a single larger population. Increased numbers of subpopulations and accelerated rates of migration slowed the loss of expected heterozygosity in all scenarios. However, there was a significant (>10%) loss in expected heterozygosity over 100 yr even at the highest rates of migration among five subpopulations of 40 animals. Our analyses predicted that while demographic stability might occur in metapopulations of 200 G. leadbeateri, considerably more individuals than this might be required to avoid a significant decline in genetic variability over 100 yr. Thus, genetic and demographic stability in G. leadbeateri occurred at different metapopulation sizes. Metapopulation structures used in our investigation were hypothetical. However, our results might emulate the dynamics of some populations of arboreal marsupials over the next century within substantial areas of wood production forests in the Central Highlands of Victoria. In many of these areas, there are now only a few and typically very small remaining patches of old‐growth forest that will provide suitable habitat for G. leadbeateri in the long term. Thus, over the next 100 yr, the species might be lost from extensive parts of its present range within montane ash forests that are utilized for timber production. Our study also indicated that there might be metapopulation structures in which the addition of subpopulations and moderate migration could have a negative effect on subpopulation persistence. These findings highlight the importance of understanding the size, number, and isolation of subpopulations that are targeted for management.

Computer simulation analyses using a generic package for population viability analysis (PVA) were used to examine the dynamics of a limited number of metapopulation structures of the mountain brushtail possum, Trichosurus caninus, and the greater glider, Petauroides volans. These arboreal marsupials inhabit tall eucalypt forests in southeastern Australia. As in a parallel study of Leadbeater's possum, Gymnobelideus leadbeateri, the results indicated that there are some metapopulation structures in which increased movement between habitat patches may have a detrimental effect on demographic stability and, in turn, reduce population persistence. These negative impacts were most pronounced in model metapopulations composed of an ensemble of very small subpopulations of 4, 10, or 20 animals. The patterns were accentuated with increased inter‐patch movement as well as the addition of further small subpopulations. These counter‐intuitive findings appear to result when animals from already unstable and declining sub‐populations disperse into unoccupied patches of habitat that act as a type of population sink. These trends in population demography were reversed in scenarios in which larger subpopulations of 40 animals were modeled. In such cases the impacts of movement and additional habitat patches on subpopulation and metapopulation dynamics were positive. In contrast to the results for various demographic parameters, increased movement and added subpopulations had a beneficial effect on genetic variability among all the types of metapopulation structures that were examined. Results for the two species were compared to each other and also with investigations of Leadbeater's possum, Gymnobelideus leadbeateri. These comparisons confirmed general trends but also revealed potential quantitative differences in the behavior of metapopulations of T. caninus, P. volans, and G. leadbeateri. Many of these differences were attributed to variations in key life history parameters such as birth and death rates, but trends in metapopulation viability did not correlate simply with intrinsic rates of population growth. The three species differed in the size of metapopulations required for demographic and genetic stability, and the rank order of their susceptibility to demographic and genetic stochasticity may not be consistent. Different species, even those within the same guild, may vary in vulnerability to disturbance and environmental perturbation. Our analyses also emphasized the need to understand the structure and composition of metapopulations in the development of strategies for conservation of wildlife at the landscape and regional scales.

In 1986, a small, outlying population of Leadbeater’s possum (Gymnobelideus leadbeateri) was discovered inhabiting lowland swamp forest at Yellingbo Nature Conservation Reserve. It is the only known extant lowland population, and occurs in habitat dramatically different to that throughout the possum’s core range in the montane ash forests of the Victorian Central Highlands. As part of an investigation into the species’ ecology in lowland swamp forest, surveys were undertaken to establish the possum’s distribution and abundance at Yellingbo. The population is estimated to contain 80 - 100 individuals, distributed along a narrow, 6 km length of riparian forest. Most of the suitable foraging habitat is presently occupied, and densities are similar to those previously reported for the species in montane ash forest. The possums are breeding year round, with significant recruitment of young into the population, and data obtained between 1995-2004 suggest that the population size is currently stable. A highly targeted revegetation program focused on the floodplain has the potential to improve up to 85 ha of degraded swamp forest, and in so doing would more than double the area of suitable habitat for G. leadbeateri in the reserve.

We used doubly labelled water to measure field metabolic rates (FMR) and water turnover rates (WTR) in one of Australia's largest native herbivores, the red kangaroo (Macropus rufus) and one of Australia's dominant livestock species, the wool-breed Merino sheep, under free-living conditions in a typical Australian rangeland. Also, we used GPS technology to examine animal space use, along with the comparisons of urine concentration, diet, diet digestibility, and subsequent grazing pressures. We found smaller space-use patterns than previously reported for kangaroos, which were between 14 and 25% those of sheep. The FMR of a 25-kg kangaroo was 30% that of a 45-kg sheep, while WTR was 15% and both were associated with smaller travel distances, lower salt intakes, and higher urine concentration in kangaroos than sheep. After accounting for differences in dry matter digestibility of food eaten by kangaroos (51%) and sheep (58%), the relative grazing pressure of a standard (mature, non-reproductive) 25-kg kangaroo was 35% that of a 45-kg sheep. Even for animals of the same body mass (35kg), the relative grazing pressure of the kangaroo was estimated to be only 44% that of the sheep. After accounting for the energetic costs of wool growth by sheep, the FMRs of our sheep and kangaroos were 2-3 times their expected BMRs, which is typical for mammalian FMR:BMRs generally. Notably, data collected from our free-living animals were practically identical to those from animals confined to a semi-natural enclosure (collected in an earlier study under comparable environmental conditions), supporting the idea that FMRs are relatively constrained within species.