Personality and plasticity predict postrelease performance in a reintroduced mesopredator

Reintroductions involve the relocation of animals into their historical range following extinction or extirpation. In this context, individuals with certain personalities may be more successful than others. For example, proactive individuals may dominate by being bolder, exploratory and more willing to take risks in familiar, stable environments (i.e. the source environment). Reactive personalities, in contrast, may thrive in novel, unstable environments (i.e. the release site) by being vigilant and risk averse. In addition, an individual's ability to adjust its behaviours over time (plasticity, or responsiveness) can play a pivotal role in determining postrelease performance. There is uncertainty, however, surrounding which behavioural measures translate to reintroduction success. We conducted behavioural assays and postrelease monitoring for eastern quolls, Dasyurus viverrinus, to determine whether behavioural measures (e.g. latency to emerge, time spent vigilant) could predict postrelease survival and dispersal in a fenced sanctuary. Using the ‘behavioural reaction norm’ approach, we found that personality derived from time spent exposed or vigilant during the assays had significant associations with postrelease den sharing and home range, while plasticity derived from latency (i.e. time delay) to reach food had a significant association with mean distance between consecutive dens. We recommend that proactive and rigid founders be preferred for initial trial reintroductions, and that reactive and plastic founders be used to supplement the population in later translocations. Our study demonstrates that, by including novelty, innovative behavioural assays offer significant value as a conservation tool to provide the fastest pathway to reintroduction success

Herbivore management for biodiversity conservation: A case study of kangaroos in the Australian Capital Territory (ACT)

Populations of macropods are higher than estimated pre-European densities in many parts of Australia. To achieve appropriate densities of macropods in the Australian Capital Territory's nature reserves, multi-tenure kangaroo management units are used to tailor management of kangaroos and total grazing pressure to achieve conservation objectives. An adaptive management framework is recommended that monitors the state of the ground-layer vegetation and alters the cull accordingly. This case study may provide insights for kangaroo management in other temperate areas of Australia

Adapting reintroduction tactics in successive trials increases the likelihood of establishment for an endangered carnivore in a fenced sanctuary

Threatened species recovery programs are increasingly turning to reintroductions to reverse biodiversity loss. Here we present a real-world example where tactics (techniques which influence post-release performance and persistence) and an adaptive management framework (which incorporates feedback between monitoring and future actions) improved reintroduction success. Across three successive trials we investigated the influence of tactics on the effective survival and post-release dispersal of endangered eastern quolls (Dasyurus viverrinus) reintroduced into Mulligans Flat Woodland Sanctuary, Australian Capital Territory. Founders were monitored for 42 days post-release, and probability of survival and post-release dispersal were tested against trial, origin, sex, den sharing and presence of pouch young. We adopted an adaptive management framework, using monitoring to facilitate rapid learning and to implement interventions that improved reintroduction success. Founders released in the first trial were less likely to survive (28.6%, n = 14) than those founders released the second (76.9%, n = 13) and third trials (87.5%, n = 8). We adapted several tactics in the second and third trials, including the selection of female-only founders to avoid elevated male mortality, and post-mating releases to reduce stress. Founders that moved dens between consecutive nights were less likely to survive, suggesting that minimising post-release dispersal can increase the probability of survival. The probability of moving dens was lower in the second and third trials, for females, and when den sharing with another founder. This study demonstrates that, through iterative trials of tactics involving monitoring and learning, adaptive management can be used to significantly improve the success of reintroduction programs

Baseline health and disease assessment of founder eastern quolls (Dasyurus viverrinus) during a conservation translocation to mainland Australia

We evaluated the health of 31 (eight males, 23 females) founder eastern quolls (Dasyurus viverrinus), translocated to a fenced reserve in the Australian Capital Territory between February 2016 and July 2017. Quolls were wild caught in Tasmania (16 animals) or captive bred at Mount Rothwell Biodiversity Interpretation Centre, Victoria (15 animals). Quolls were assessed for the presence of selected potential pathogens (Toxoplasma gondii, herpesviruses, Salmonella serovars, hemoprotozoa, and ectoparasites). We assessed the relationships among sex, provenance (captive or free ranging), T. gondii or herpesvirus infection, weight, and hematologic and biochemical variables. Six of 21 quolls (29%) tested were seropositive for antibodies to T. gondii. Seropositive quolls weighed significantly more and had significantly lower potassium levels, anion gaps, and urea and triglyceride levels than seronegative quolls had. Eighteen of 31 (58%) combined conjunctival-pharyngeal-cloacal swabs collected from quolls were PCR positive for a newly identified gammaherpesvirus, tentatively named dasyurid gammaherpesvirus 3. There were no significant differences among hematologic and biochemical variables or body weights from PCR-positive and PCR-negative quolls. Eighteen of 18 (100%) of rectal-swab samples were culture negative for Salmonella serovars. Three species of tick (Ixodes tasmani, Ixodes fecialis, and Ixodes holocyclus), two species of mite (Andreacus radfordi, one unidentified), and four species of flea (Pygiopsylla hoplia, Acanthopsylla rothschildi rothschildi, Uropsylla tasmanica, and Stephanocircus dasyuri), were detected on wild-caught quolls, whereas a fifth species of flea, Echidnophaga myremecobii, was detected only on captive-bred quolls. Five of 15 blood samples (33%) were positive for hemoprotozoan DNA via PCR, a novel Hepatozoon species, a novel Theileria species, Theileria paparinii, and Trypanosoma copemani were detected. Despite the presence of several potential pathogens known to be associated with disease in other marsupials, the quolls were considered to be in good general health, suitable for translocation, and a viable population was subsequently established

The ‘Goldilocks Zone’ of predation: The level of fox control needed to select predator resistance in a reintroduced mammal in Australia

A large component of the anthropogenic biodiversity crisis is the loss of animal species. In response, there has been significant investment in reintroductions of species to their historical ranges. Predation by native and exotic predators, however, remains a barrier to success. Over the past 200 years, Australia has seen the highest rate of mammal extinction on earth, with mammals within a critical weight range (CWR: 35 g–5.5 kg) most affected due to predation by exotic predators. Populations of some threatened species now exist only in Tasmania, offshore islands, or predator-proof sanctuaries. The next critical step is to return native populations outside of predator-free areas, ‘beyond-the-fence’, on the continental mainland. Given our current inability to completely remove exotic predators from mainland ecosystems, how can we achieve successful mammal reintroductions? A potential solution is to drive adaptation of reintroduced animals towards predator-resistance by exposing them to low levels of predation. We propose the concept of a ‘Goldilocks Zone’—the ‘just right’ levels of predation needed to drive selection for predator-resistant native species, while ensuring population viability. We experimentally reintroduced a mammal, the eastern bettong (Bettongia gaimardi), to mainland Australia, 100 years after its local extinction. Using an intense baiting regime, we reduced the population density of the red fox (Vulpes vulpes), the main factor behind the eastern bettong’s extirpation from the continent. Reducing bait take to 15% of previous levels allowed differential survival among bettongs; some surviving under 100 days and others over 450 (~ 4 times longer than some similar trials with related species). Surviving individuals were generally larger at release than those that died earlier, implying selection for larger bettongs. Our results suggest that reducing predation could establish a Goldilocks Zone that could drive selection for bettongs with predator-resistant traits. Our work contributes to a growing body of literature that explores a shift towards harnessing evolutionary principles to combat the challenges posed by animal management and conservation

Transition to density dependence in a reintroduced ecosystem engineer

When does a reintroduced population of animals become self-regulating? Quantifying this is critical in determining when interventions can be tapered off, or when they may need to be reinstated. We tracked the growth trajectory of a reintroduced population to establish whether it was irruptive and/or had transitioned to self-regulation. In 2012, we reintroduced 32 eastern bettongs (Bettongia gaimardi), a potoroid marsupial from Tasmania, Australia, to a 485 ha exotic predator-proof fenced reserve in the Australian Capital Territory. We established a 92 cage trap monitoring network to track population growth between the Austral Autumn 2014 and Summer 2018. We used capture-recapture models to track changes in the population through time, and modelled ‘bettong weight’, ‘pouch occupancy’ and ‘age of pouch young’ with population variation, to establish potential associations with changes in population size. The estimated population grew from 32 individuals in 2012 to 100 in 2014, 192 in Autumn 2016, and then declined to 151 in Summer 2018. Estimated survival of adults was high—above 92% between most sessions. Adult female weights ranged between 0.485 and 2.428 kg, and adult males between 0.470 and 2.775 kg. Our study showed density dependence was achieved over the 6 year period. Low adult mortality, and variable pouch occupancy related to female weight, suggested that food availability had influenced lactation in females, with flow-on impacts on juvenile survival. Long-term, broad-scale population dynamics were probably driven by a mix of direct (e.g. disease, harvesting for other reintroductions), and indirect (i.e. climate dependent availability of nutritious food) influences on population size