Causes of reintroduction failure of the brown treecreeper: Implications for ecosystem restoration

Brief exposure to captivity in a songbird is associated with reduced diversity and altered composition of the gut microbiome

The gut microbiome is important for host fitness and is influenced by many factors including the host's environment. Captive environments could potentially influence the richness and composition of the microbiome and understanding these effects could be useful information for the care and study of millions of animals in captivity. While previous studies have found that the microbiome often changes due to captivity, they have not examined how quickly these changes can occur. We predicted that the richness of the gut microbiome of wild-caught birds would decrease with brief exposure to captivity and that their microbiome communities would become more homogeneous. To test these predictions, we captured wild house sparrows (Passer domesticus) and collected fecal samples to measure their gut microbiomes immediately after capture ("wild sample") and again 5-10 days after capture ("captive sample"). There were significant differences in beta diversity between the wild and captive samples, and captive microbiome communities were more homogenous but only when using nonphylogenetic measures. Alpha diversity of the birds' microbiomes also decreased in captivity. The functional profiles of the microbiome changed, possibly reflecting differences in stress or the birds' diets before and during captivity. Overall, we found significant changes in the richness and composition of the microbiome after only a short exposure to captivity. These findings highlight the necessity of considering microbiome changes in captive animals for research and conservation purposes.

On the road to self-sustainability: reintroduced migratory European northern bald ibises Geronticus eremita still need management interventions for population viability

The northern bald ibis Geronticus eremita disappeared from Europe in the Middle Ages. Since 2003 a migratory population has been reintroduced in Central Europe. We conducted demographic analyses of the survival and reproduction of 384 northern bald ibises over a period of 12 years (2008–2019). These data also formed the basis for a population viability analysis simulating the possible future development of the northern bald ibis population under different scenarios. We analysed life stage-specific survival rates, rearing protocols and colonies, and the influence of stochastic catastrophic events and reinforcement translocations on population growth. Life stage-specific survival probabilities were 0.64–0.78. Forty-five per cent of the mature females reproduced, with a mean fecundity of 2.15 fledglings per nest. The complementary population viability analysis indicated that the Waldrappteam population is close to self-sustainability, with an estimated population growth rate of 0.95 and a 24% extinction probability within 50 years. Of the 326 future scenarios tested, 94% reached the criteria of extinction probabilities < 5% and population growth rates > 1. Stochastic catastrophic events had only a limited effect. Despite comparatively high survival and fecundity rates the population viability analysis indicated that to achieve self-sustainability the Waldrappteam population needs further translocations to support population growth and the implementation of effective measures against major mortality threats: illegal hunting in Italy and electrocution on unsecured power poles. The findings of this study are to be implemented as part of a second European LIFE project.

Assessing species reintroduction sites based on future climate suitability for food resources

The reintroduction of a species that is extinct in the wild demands caution because reintroduction locations may be associated with threats, such as hunting, poor-quality habitat, and climate change. This is the case for Cyanopsitta spixii (Spix's Macaw), which has been extinct in the wild since 2000. The few living individuals were created in captivity and will be used in a reintroduction project within the species' original distribution area, the Caatinga domain (Brazil). Because the occurrence records for this bird are old and inaccurate, we investigated the current and future environmental suitability of the 14 plant species used by C. spixii as resource. These plants are key elements for the long-term reestablishment of the species in the wild, so the use of models helps in the assessment of the effects of climate change on the availability of these resources for the species and informs selection of the best places for reintroduction. We based our models of environmental suitability on 19 bioclimatic variables and nine physical soil and topography variables. Climate projections were created for the present and for the year 2070 with an optimistic (SSP2-4.5) and a pessimistic (SSP5-8.5) climate scenario. Both future climate scenarios lead to a reduction in area of environmental suitability that overlapped for all the plant species: 33% reduction for SSP2-4.5 and 63% reduction for SSP5-8.5. If our projections materialize, climate change could thus affect the distribution of key resources, and the maintenance of C. spixii would depend on restoration of degraded areas, especially riparian forests, and the preservation of already existing natural areas. The Caatinga domain is very threatened by habitat loss and, for the success of this reintroduction project, the parties involved must act to protect the species and the resources it uses.

Can evolutionary theories of dispersal and senescence predict postrelease survival, dispersal, and body condition of a reintroduced threatened mammal?

Theories of dispersal and senescence (or aging) predict that dispersal, and ongoing survival and body condition, are influenced by evolutionary drivers, along with intrinsic and extrinsic factors. Such theories are relevant to translocations of animals where high mortality, loss of body condition, and dispersal beyond the area of release are commonly reported. However, these theories have rarely been tested using data from translocations.We explore whether theories of dispersal and senescence, together with biological knowledge and management interventions, can predict rates of postrelease dispersal, survival and change in body condition of a translocated endangered meso-predator, the eastern quoll Dasyurus viverrinus.Captive-bred quolls (n = 60) from three sanctuaries were translocated to an unfenced, predator-managed reserve (Booderee National Park) over 2 years (2018, 2019). Survival, dispersal and body mass were monitored via GPS/VHF tracking and targeted trapping for 45 days postrelease.We found support for the "social subordinate" hypothesis, with smaller quolls dispersing further. Consistent with theories of senescence and the biology of our species, survival was marginally greater for females, and females regained losses in body mass in both years following release. In contrast, males recovered body condition in the first but not the second release as this coincided with breeding. Quolls that originated from the mainland sanctuary were on average heavier at release and, after accounting for weight, dispersed further. Synthesis and applications. Using theory to test outcomes of wildlife translocations can provide insights into patterns across taxa and under different conditions, enabling useful improvements to future fauna translocations. This allows for better predictions to be made about the likelihood of success from proposed translocations, changes to planning to improve outcomes (e.g., modifying sex ratios, individual selection and release cohort), and improved animal welfare as fewer animals are subjected to trials.

Conservation implications of using an imitation carnivore to assess rarely used refuges as critical habitat features in an alpine ungulate

Understanding relationships between animals and their habitat is a central goal in ecology with important implications for conservation. Misidentified habitat requirements can have serious repercussions because land protection or reintroductions might occur in less than optimal habitat. Studies of resource selection have greatly facilitated an understanding of ecological relationships but can be improved when vital yet infrequently utilized habitat features are more fully described. A critical element for many prey species is escape terrain or some other form of refuge to avoid predation. Mountain goats (Oreamnos americanus) are well known for their use of cliffs to avoid predation, but a survey of the literature revealed at least twelve different approximations of goat escape terrain, ranging from > 25° to > 50° slopes. Here, we seek to (1) enhance estimates of mountain goat escape terrain and antipredator behavior, and (2) highlight the limitations of the assumption that the time an animal spends in an area is proportional to importance. To improve estimates of goat escape terrain, we conducted field work across two years (2014–15) in Glacier National Park, Montana USA and manipulated apparent predation risk by exposing mountain goats to a threatening simulated grizzly bear (Ursus arctos) treatment and a non-threatening ungulate (control) treatment. Mountain goats moved in response to the simulated bear but not in response to the simulated ungulate, with shorter latencies to move for subjects in larger groups and at shorter distances to the simulated threat. Through a used-unused resource selection function we tested 22 landscape variables to describe the use of escape terrain. Proximity to slopes greater than 60° best explained the locations to which mountain goats fled after exposure to the simulated bear, and the average slope of these escape locations was 56.5° (±14.1 S.D.). Our results suggest that mountain goat escape terrain be considered at slopes of 60° as a minimum because our simulated threat did not include pursuit of goats and, thus, slopes of 60° are likely underestimates of actual escape terrain. Additionally, because direct interactions between carnivores and goats seldom occur, serious escape terrain is infrequently used. Past estimates of escape may have miscalculated the slopes which goats select for in response to predation risk. Based on experimental approaches in the wild, we suggest that anti-predator behavior should be included in studies of resource selection when the goal is to consider habitat as a predictor for conservation success. Finally, we discuss evidence suggesting a past mountain goat introduction failed due to lack of adequate escape terrain and subsequent recolonization of a predator.

Release site selection: reintroductions and the habitat concept

Identifying release sites with good habitat quality is one of the most important steps in any reintroduction project. However, despite their wide application in legislation and research, the habitat concept and habitat-related terms remain poorly defined and subject to confusion. Reviewing a variety of definitions, we advocate for understanding habitat as an area with a species-specific set of resources and environmental conditions that enable a population to persist and reproduce. Using this understanding we investigated release site selection as well as the usage of the term habitat and other habitat-related terms in 324 reintroduction case studies and reintroduction policy documents published during January 1990–May 2016. Although the use of the habitat concept in these publications remained mostly unclear because of the lack of definitions provided, we found an overall improvement in the quality of reintroduction site assessment, and a shift towards more systematic approaches, such as habitat modelling and experimental translocation. To further improve reporting on release site selection, we recommend updating IUCN reintroduction publications and encouraging practitioners to consider the spatial and temporal heterogeneity of habitat, as well as the multiple scales at which a species selects its habitat, in the design of a release site assessment.

Habitat selection and behaviour of a reintroduced passerine: linking experimental restoration, behaviour and habitat ecology

Habitat restoration can play an important role in recovering functioning ecosystems and improving biodiversity. Restoration may be particularly important in improving habitat prior to species reintroductions. We reintroduced seven brown treecreeper (Climacteris picumnus) social groups into two nature reserves in the Australian Capital Territory in south-eastern Australia. This study provided a unique opportunity to understand the interactions between restoration ecology, behavioural ecology and habitat ecology. We examined how experimental restoration treatments (addition of coarse woody debris, variations in ground vegetation cover and nest box installation) influenced the behaviour and microhabitat use of radio-tracked individuals to evaluate the success of restoration treatments. The addition of coarse woody debris benefited the brown treecreeper through increasing the probability of foraging on a log or on the ground. This demonstrated the value of using behaviour as a bio-indicator for restoration success. Based on previous research, we predicted that variations in levels of ground vegetation cover would influence behaviour and substrate use, particularly that brown treecreepers would choose sites with sparse ground cover because this allows better access to food and better vigilance for predators. However, there was little effect of this treatment, which was likely influenced by the limited overall use of the ground layer. There was also little effect of nest boxes on behaviour or substrate use. These results somewhat confound our understanding of the species based on research from extant populations. Our results also have a significant impact regarding using existing knowledge on a species to inform how it will respond to reintroduction and habitat restoration. This study also places great emphasis on the value of applying an experimental framework to ecological restoration, particularly when reintroductions produce unexpected outcomes.