The effect of pre-release captivity on the stress physiology of a reintroduced population of wild eastern bettongs

Stress is important in reintroduction biology because it can influence mortality, dispersal and recruitment and determine establishment success. As stress is unavoidable during reintroduction, it requires deliberate management. Release tactics (e.g. ‘delayed- and immediate-release’) are often selected specifically based on their presumed effect on physiological stress, yet, the actual physiological effects are seldom tested. Delayed-release involves pre-release confinement (in situ), or captivity (ex situ), which can improve post-release performance in some cases, or induce a detrimental effect in others, especially in wild animals. Quarantine is another common pre-release practice that requires captivity/confinement carrying similar post-release physiological implications. We use faecal glucocorticoid metabolite concentrations (FGM) to evaluate how a delayed-release involving 95–345 days in captivity influences the stress physiology of wild eastern bettongs (Bettongia gaimardi), compared to an immediate-release (within 24 h of capture), across the initial 18 months post-release. The results suggest that FGM concentrations were relatively higher in the delayed-release group at release, but significantly lower after ca. 2 months of release. We assessed seasonal fluctuations in FGM concentrations, the effect of release tactics on in-trap behaviour, and the relationship between those behaviours and FGM concentrations. We found that FGM concentrations fluctuated seasonally, but release tactics did not influence behaviour, and that behavioural variations had no relationship with FGM concentrations. Overall our results, coupled with previous research, suggest that an immediate-release is preferable when quarantine is not required

Establishment, persistence and the importance of longitudinal monitoring in multi-source reintroductions

Incorporating genetic data into conservation programmes improves management outcomes, but the impact of different sample grouping methods on genetic diversity analyses is poorly understood. To this end, the multi-source reintroduction of the eastern bettong Bettongia gaimardi was used as a long-term case study to investigate how sampling regimes may affect common genetic metrics and hence management decisions. The dataset comprised 5307 SNPs sequenced across 263 individuals. Samples included 45 founders from five genetically distinct Tasmanian source regions, and 218 of their descendants captured during annual monitoring at Mulligan’s Flat Woodland Sanctuary (121 samples across eight generations) and Tidbinbilla Nature Reserve (97 samples across nine generations). The most management-informative sampling regime was found to be generational cohorts, providing detailed long-term trends in genetic diversity. When these generation-specific trends were not investigated, recent changes in population genetics were masked, and it became apparent that management recommendations would be less appropriate. The results also illuminated the importance of considering establishment and persistence as separate phases of a multi-source reintroduction. The establishment phase (useful for informing early adaptive management) should consist of no less than two generations and continue until admixture is achieved (admixture defined here as >80% of individuals possessing >60% of source genotypes, with no one source composing >70% of >20% individuals’ genotype) is achieved. This ensures that the persistence phase analyses of population trends remain minimally biased. Based on this case study, we recommend that emphasis be given to the value of generationally specific analyses, and that conservation programmes collect DNA samples throughout the establishment and persistence phases and avoid collecting genetic samples only when the analysis is imminent. We also recommend that population genetic analyses for multi-source reintroductions consider whether admixture has been achieved when calculating descriptive genetic metrics

Countering ecological misconceptions with strategic translocation and assessment of microhabitat use

Wildlife translocations to human-modified and inferred formerly occupied habitats can be controversial when they involve a high degree of perceived risk of failure, often stemming from a large number of unknowns or misconceptions regarding the focal species' ecology. However, it is increasingly recognised that such translocations are necessary to guide effective conservation strategies, particularly for species that persist in a subset of the habitats they formerly occupied. As a step towards alleviating some of the perceived risks around these translocations, we suggest the focal species' microhabitat use in the recipient locality of a trial translocation be compared with that where they still persist. Using a case study of a threatened Australian rodent, the pookila (Pseudomys novaehollandiae, New Holland mouse), we demonstrate how such an assessment can shed light on ecological misconceptions that may need to be addressed, and bring about the revision of species-specific recommendations for restoration works and release tactics. Feeding this knowledge back into the decision-making process, practitioners may more confidently direct future conservation activities (including further trial translocations) across a broader diversity of habitats within the species' indigenous range. Widespread and systematic implementation of this approach may help to reverse the impacts of shifting baseline syndrome, and should ultimately aid the resilience of species to future environmental change

Landscapes of nausea: Successful conditioned taste aversion in a wild red fox population

Predation by invasive mammalian species is one of the key drivers of native species' population declines and extinctions. Current management of invasive species focuses on their removal from the landscape. However, total removal can be difficult, costly and even impossible. If eradication is not achieved, reductions in predator numbers are often temporary. New tactics are needed to target predators in situ, to reduce their negative impacts. We test the efficacy of conditioned taste aversion (CTA), a tactic that could reduce the impact of predation on target prey species. By associating nausea with a specific food source, it may be possible to condition an aversion to a target bait, and ultimately to live animals in the wild. To assess if wild invasive red foxes (Vulpes vulpes) can be conditioned to avoid a specific food source, we used baits (fried deboned chicken) containing encapsulated levamisole, an anthelmintic agent known to induce nausea leading to emesis and/or diarrhea at high dosages with no long-term side effects. We buried baits at 30 stations across an open landscape. After treatment, reductions in control baits taken (at least 30%) were observed for 68 days, indicating the use of CTA had successfully reduced bait consumption by red foxes in a wild context. To our knowledge, this study represents the first successful test of CTA to a meat bait in a wild red fox population. Our results suggest that CTA shows promise as a tool to reduce the predation of vulnerable animals providing an alternative tactic to manage the impacts of invasive mammalian predators where eradication is currently impossible

Mini Safe Havens for population recovery and reintroductions ‘beyond-the-fence’

In response to the ongoing decline of fauna worldwide, there has been growing interest in the rewilding of whole ecosystems outside of fenced sanctuaries or offshore islands. This interest will inevitably result in attempts to restore species where eliminating threats from predators and competitors is extremely challenging or impossible, or reintroductions of predators that will increase predation risk for extant prey (i.e., coexistence conservation). We propose ‘Mini Safe Havens’ (MSHs) as a potential tool for managing these threats. Mini Safe Havens are refuges that are permanently permeable to the focal species; allowing the emigration of individuals while maintaining gene flow through the boundary. Crucial to the effectiveness of the approach is the ongoing maintenance and monitoring required to preserve a low-to-zero risk of key threats within the MSH; facilitating in-situ learning and adaptation by focal species to these threats, at a rate and intensity of exposure determined by the animals themselves. We trialled the MSH approach for a pilot reintroduction of the Australian native New Holland mouse (Pseudomys novaehollandiae), in the context of a trophic rewilding project to address potential naïveté to a reintroduced native mammalian predator. We found that mice released into a MSH maintained their weight and continued to use the release site beyond 17 months (525 days) post-release. In contrast, individuals in temporary soft-release enclosures tended to lose weight and became undetectable approximately 1-month post-release. We discuss the broad applicability of MSHs for population recovery and reintroductions ‘beyond-the-fence’ and recommend avenues for further refinement of the approach

Analyzing captive breeding outcomes to inform reintroduction practice: Lessons from the pookila (Pseudomys novaehollandiae)

Captive breeding is often used to produce individuals for reintroduction programs in order to reestablish a species in an area where it has become locally extinct. To maximize the likelihood of establishing a self-sustaining population in the wild, an analysis of data from captive breeding programs is commonly undertaken to (1) increase the quantity of individuals and rate at which they can be released, and (2) maintain or improve the genetic and phenotypic quality of individuals. Here we demonstrate how the knowledge gained from these analyses can also be applied to decision-making during the design of subsequent reintroductions to further advance a reintroduction program toward success. We conducted an analysis of data from a captive breeding program for the threatened pookila (Pseudomys novaehollandiae, New Holland mouse) spanning 6 years. We found evidence for relationships between the reproductive output of pookila and behavioral, demographic, experiential, health, and physiological predictors. Based on a biological interpretation of these results, and with reference to a checklist of all known translocation tactics, we recommend 11 specific design elements to maximize the probability of pookila reproduction postrelease (thereby improving the likelihood of reintroduction success). These recommendations should be interpreted as hypotheses to be evaluated and refined in future reintroduction trials for the pookila. The uncertainty around the postrelease survival and reproduction of a species that is common in reintroduction practice warrants the creative use of existing data to inform adaptive management. Indeed, there is a wealth information in well-kept captive breeding records that is currently underused by reintroduction practitioners. The direct integration of knowledge derived from captive breeding (where available) with decision-making for reintroductions, as described here, will help navigate these uncertainties, which would benefit the conservation of both understudied and well-known species around the world

Roadmap to recovery revealed through the reintroduction of an IUCN Red List species

Reintroductions are powerful tools for tackling biodiversity loss, but the resulting populations can be intrinsically small and vulnerable. It is therefore critical to maximise the number of individuals that are available to contribute to recovery efforts. To address this, we investigated how demographic parameters from a reintroduced population can reveal threats to long-term persistence, inform thresholds for management interventions, and create targets for removing an endangered species from the IUCN Red List. We calculated capture-mark-recapture population estimates for eastern quolls (Dasyurus viverrinus) which had been reintroduced to a fenced reserve in the Australian Capital Territory. We then incorporated the resulting demographic parameters into population viability analyses (PVAs) to estimate probabilities of persistence under several scenarios, including supplementations and harvests (removal of individuals for translocation to other locations). After determining sustainable harvest rates, we then ‘back-cast’ the population size and occupancy area required to remove the species from the IUCN Red List within 10 years. Our demographic results indicated high mean apparent survival (90% ± 5), and PVAs revealed the probability of persistence over a 50-year time horizon was 50.5% with no interventions, 0% when the population was harvested of > 6 individuals, and 100% if harvests ≤ 54 juveniles were combined with an annual supplementation of ten maternal females (with ≤ 6 young each). Based on this model, a total harvest area of 413 km2 and an occupancy area of 437 km2 would be needed to recover the species within 10 years (i.e., 90 similar fenced reserves, not accounting for edge effects). Due to the inherent difficulty in securing large areas for species recovery, we see these ambitious targets as a call to create coordinated and collaborative sanctuary networks where species can be managed as a metapopulation across multiple sites. By taking advantage of a rapid life history and harvesting the ‘doomed surplus’, managers can achieve their stretch goals for species recovery in the long term

Trends in animal translocation research

Translocations are an important conservation tool that enable the restoration of species and their ecological functions. They are particularly important during the current environmental crisis. We used a combination of text-analysis tools to track the history and evolution of the peer-reviewed scientific literature on animal translocation science. We compared this corpus with research showcased in the IUCNs Global Conservation Translocation Perspectives, a curated collection of non-peer-reviewed reintroduction case studies. We show that the peer-reviewed literature, in its infancy, was dominated by charismatic species. It then grew in two classical threads: management of the species of concern and management of the environment of the species. The peer-reviewed literature exhibits a bias towards large charismatic mammals, and while these data are invaluable, expansion to under-represented groups such as insects and reptiles will be critical to combating biodiversity loss across taxonomic groups. These biases were similar in the Translocation Perspectives, but with some subtle differences. To ensure translocation science can address global issues, we need to overcome barriers that restrict this research to a limited number of countries