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Spatial ecology informs reintroduction tactics for warabin (Burhinus grallarius; bush stone-curlew)
Abstract
This thesis provides a case-study using an initial reintroduction to inform tactic selection for future translocations. Warabin (Burhinus grallarius) have declined substantially in southern Australia due to habitat loss and predation by feral predators (largely foxes, Vulpes vulpes) and now occupy a subset of their former niche. They have been successfully reintroduced to a fenced reserve, Mulligans Flat Woodland Sanctuary (MFWS), which provides an opportunity to assess their habitat requirements and movement behaviours.
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 km ² and an occupancy area of 437 km ² 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.
Unlabelled:
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.
Supplementary information:
The online version contains supplementary material available at 10.1007/s10531-022-02495-6.
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.
Global biodiversity losses continue despite tremendous growth in the volume of conservation science and many local successes. Research that can achieve conservation science's aims—arresting declines in biodiversity and preventing extinctions—is therefore of ever greater importance. Here, we ask whether conservation science, as currently performed, is progressing in such a way as to maximize its impact. We present a simple framework for how effective conservation research could progress, from identifying problems to diagnosing their proximate and ultimate causes, and from proposing, to designing, implementing, and testing responses. We then demonstrate that for three well‐known examples—South Asian vultures, whooping cranes, and bycatch of procellariform seabirds—published studies appear to follow this sequence, with considerable benefits. However, for a representative sample of the wider conservation literature, we find no evidence of such a progression. Instead, the vast majority of papers remain focused on describing the state of nature or on mechanisms directly causing changes, with very little research on designing or implementing conservation responses. This lack of research on the sorts of questions that might most help conservation science deliver its stated mission strongly suggests we will struggle to translate the huge increase in research activity into real‐world benefits.
Simplification of stand structure of forests and woodlands through human-induced modification is a serious threat to biodiversity. Restoring lost habitat complexity and heterogeneity, such as woody debris, requires an understanding of the relationships between different elements that contribute to stand structure. In this study, we examine the structure and composition of a critically endangered box-gum grassy woodland in south-eastern Australia and relationships with woody debris loads. We found that: (1) despite modification by humans and differing susceptibility to dieback, the two dominant tree species, Blakeley’s red gum, Eucalyptus blakelyi and yellow box, E. melliodora, occurred in similar proportions irrespective of vegetation density; (2) E. blakelyi had the largest number of stems and basal area, but while E. melliodora had fewer stems, it had a similar basal area to E. blakelyi. E. melliodora also showed fewer signs of dieback than E. blakelyi with between 40–50% trees in good condition compared to 2% for the latter species; (3) woody debris loads were low compared to other studies in woodland, but there were levels of heterogeneity indicating ‘natural’ accumulation was occurring; (4) tree basal area and woody debris loads had a 1:1 relationship across all sites and vegetation densities. Overall, our study indicated that ecosystem recovery was taking place (i.e. with many young trees), but there were fewer large trees that are known to supply most woody debris. Our findings highlight the slow accumulation of this critical resource because the volumes were lower than expected. Based on our results, we recommend: (1) aiming for approximately a 50:50 ratio of yellow box to Blakely's red gum basal area in woodland restoration projects; (2) to accelerate the recovery of woodland structure, addition of woody debris should be added at a minimum ratio of 1:1 to standing basal area (i.e. a basal area of 5.99 m² requires a minimum volume of 3.11 m³) (3) managing for both volume and heterogeneity of woody debris loads; (4) preserving large diameter trees to harness proportionally higher woody debris and litter inputs.
Introduced predators are a serious threat to Australian vertebrates. However, the consequences of predation for the avifauna have rarely been quantified. We took advantage of the establishment of a 7,832 ha fox‐ and cat‐free safe haven at Mt. Gibson, in Western Australia, to assess the consequences of excluding introduced mammal predators on the bird fauna. Bird surveys were conducted over six years, before and after the establishment of the introduced predator‐free safe haven. After three years, half the sites were enclosed by the fence that excluded introduced predators, while the remainder of sites remained outside the fence and were exposed to fox and cat activity. The sites were stratified by four major vegetation types. A total of 91 bird species were variously detectable with the survey approach, but were typically more detectable during morning surveys. Site occupancy varied considerably among species, but overall, occupancy by all species was most likely to be either not impacted or positively impacted by the safe haven. The most notable change was that avifaunal richness appeared to increase in woodland and shrubland habitats within, as compared to outside, the safe haven. We conclude that: (1) the safe haven had an overall positive impact on bird occupancy; and (2) there were no consistent trends with respect to the kinds of species whose occupancy was positively impacted, beyond them all being small‐ to medium‐sized birds and mostly insectivorous. However, these conclusions must be tempered by the poor detection probability of many species. This article is protected by copyright. All rights reserved.
Grasslands and grassy woodlands worldwide have experienced declines in extent and condition, with substantial changes to their ground-layer biodiversity. In Australia, this decline has coincided with the extinction of many digging mammals that may have once created regeneration niches for native ground layer plants. These digging mammals are widely recognised as ‘ecosystem engineers’, due to their influence on biopedturbation and resultant soil functions. Yet there is uncertainty as to the benefits of digging in restoring grassland diversity with current levels of modification and the presence of exotic plants. We investigated the effect of digging by the reintroduced eastern bettong (Bettongia gaimardi) on seedling germination in a temperate grassy woodland in south-eastern Australia. We marked fresh bettong foraging pits and undisturbed control plots in dense and open grassland. We added seeds of seven native forb species and monitored germination and establishment over 2 years. We found significantly more seedlings in bettong pits than controls, particularly in dense grassland. This effect persisted beyond 1 year, suggesting that pits may have increased seedling survival in dry conditions. Surprisingly, native species displayed a stronger positive response to pits than exotic species, particularly in a wet year. There was an initial reduction in exotic species, but this was followed by their increase in 1-year-old pits, suggesting that the disturbance created by digging could eventually lead to an increase in weed abundance. Our results demonstrate that while bettong pits provide a germination niche for native forbs, reintroducing digging animals will not necessarily result in the desired restoration outcomes. Ongoing persistence of exotic species is to be expected, and seed addition may be required for species that are seed-limited.
Digging animals may alter many characteristics of their environment as they disrupt and modify the ground’s surface by creating foraging pits or burrows. Extensive disturbance to the soil and litter layer changes litter distribution and availability, potentially altering fuel loads. In many landscapes, including peri‐urban areas, fire management to reduce fuel loads is complex and challenging. The reintroduction of previously common digging animals, many of which are now threatened, may have the added benefit of reducing fuel loads. We experimentally examined how the reintroduction of a marsupial bandicoot, quenda (Isoodon fusciventer), altered surface fuel loads in an urban bush reserve in Perth, Western Australia. Foraging activities of quenda (where they dig for subterranean food) were substantial throughout the reserve, creating a visibly patchy distribution in surface litter. Further, in open plots where quenda had access, compared to fenced plots where quenda were excluded, quenda foraging significantly reduced litter cover and litter depth. Similarly, estimated surface fuel loads were nearly halved in open plots where quenda foraged compared to fenced plots where quenda were absent (3.6 c.f. 6.4 tonnes ha‐1). Fire behaviour modelling, using the estimated surface fuel loads, indicated the predicted rate of spread of fire were significantly lower for open plots where quenda foraged compared to fenced plots under both low (29.2 c.f. 51.4 m hr‐1; total fuels) and high (74.3 c.f. 130.4 m hr‐1; total fuels) fire conditions. Although many environments require fire, including the bushland where this study occurred, fire management can be a considerable challenge in many landscapes, including urban bushland reserves which are usually small and close to human infrastructure. The reintroduction of previously common digging species may have potential value as a complimentary tool for reducing fuel loads, and potentially, fire risk.
Temperate grasslands and woodlands are the focus of extensive restoration efforts worldwide. Reintroduction of locally extinct soil-foraging and burrowing animals has been suggested as a means to restore soil function in these ecosystems. Yet little is known about the physical and chemical effects of digging on soil over time and how these effects differ between species of digging animal, vegetation types or ecosystems. We compared foraging pits of a native reintroduced marsupial, the eastern bettong ( Bettongia gaimardi ) and that of the exotic European rabbit ( Oryctolagus cuniculus ). We simulated pits of these animals and measured pit dimensions and soil chemical properties over a period of 2 years. We showed that bettong and rabbit pits differed in their morphology and longevity, and that pits had a strong moderating effect on soil surface temperatures. Over 75% of the simulated pits were still visible after 2 years, and bettong pits infilled faster than rabbit pits. Bettong pits reduced diurnal temperature range by up to 25 °C compared to the soil surface. We did not find any effects of digging on soil chemistry that were consistent across vegetation types, between bettong and rabbit pits, and with time since digging, which is contrary to studies conducted in arid biomes. Our findings show that animal foraging pits in temperate ecosystems cause physical alteration of the soil surface and microclimatic conditions rather than nutrient changes often observed in arid areas.
The critically endangered and iconic plains-wanderer (Pedionomus torquatus) is phylogenetically distinct and endemic to south eastern Australia, and is a high conservation priority. Furthermore, it relies on critically-endangered native grasslands for its survival, which vary temporally in structure and hence do not always provide suitable habitat. To manage the remaining native grasslands appropriately, it is essential to understand the temporal and spatial dynamics of plains-wanderer habitat preferences. We monitored plains-wanderers and habitat measurements for nine years to link habitat preferences to specific elements of grassland structure. We also observed habitat selection by plains-wanderers at two spatial scales – sites (paddocks) and at microsites (immediate vicinity of the birds). The plains-wanderer population declined rapidly after a dramatic increase in native grass cover in 2011, and recovery of the population since then has been slow. In 2015/16, plains-wanderers were generally encountered at microsites with higher bare ground and cryptogam cover. However, at the site scale, paddocks with plains-wanderers had similar cover of native grass and bare ground than those without plains-wanderers. The results suggest that observation of highly-localised habitat components alone may mask aspects of the habitat selection occurring at larger spatial scales. Plains-wanderers may require areas of denser perennial grass for nesting and shelter, as well as access to the open areas where they are commonly encountered. We discuss how private land used for commercial grazing may be crucial to plains-wanderer conservation. The results also prompt consideration of how we measure and interpret habitat selection for grassland birds globally.
Long-term faunal responses to restoration efforts can be very different from those in the short term, but are often not quantified systematically to identify ways that maximise restoration outcomes. We report on a 9-year landscape-scale ecological experiment that tests the long-term responses of reptile populations to coarse woody debris (CWD) addition, reduced native macropod grazing, and prescribed fire. We found that reptile species richness was increased 9 years after CWD addition, as was the abundance of several common reptile species. Further, the more CWD was added to the system, the more benefits were afforded to reptiles. The positive effect of CWD depended on the surrounding vegetation structure and was greater in sites with low tree and shrub cover. Further, lower levels of macropod grazing appeared to lessen the effects of CWD addition in the long term. Our results show that restoration projects in open woodlands and scattered tree ecosystems should consider the addition of CWD as a fundamental element of their management actions. To maximise benefits of CWD addition for reptiles, we recommend a strategy of placing CWD in areas with low tree and shrub cover rather than areas with high tree and shrub cover. The addition of CWD in such areas would provide crucial shelter and foraging substrates for reptiles in a comparatively hostile portion of the landscape. Our study helps to establish guidelines for achieving long-lasting effects of ecosystem restoration for vertebrates and demonstrates the benefits of monitoring vertebrates over the long term.
The highly interactive nature of predator-prey interactions is essential for ecosystem conservation; however predators are disappearing from entire ecosystems all over the Earth. Reintroduction is as a management technic to reverse this trend. Ecological Niche Models (ENM) are a preemptive tool to release- site selection, which can also improve conservation strategies by defining habitat quality levels. The Atlantic Forest Biodiversity hotspot is losing its top predators, and Harpy Eagles Harpia harpyja – Earth largest eagle – are now limited to few forest pockets. Harpy Eagles are widespread on Amazon Forest, where habitat loss and degradation is advancing at a fast pace. We aim to access the suitability of currently available Atlantic Forest to Harpy Eagle reintroduction, as well as to describe the varying suitability of threatened Amazonian landscapes to this key predator. Here we show that the best section for Harpy Eagle reintroduction in Atlantic Forest is the Paranaguá-Serra do Mar protected areas; and that much of habitat has been lost in Amazonia with the advance of the Arc of Deforestation. At Paranaguá-Serra do Mar forest corridor, Harpy Eagles could reinstall behavioral and demographic control over primates which are damaging vegetation. Reintroduction and extensive captive breeding programs have taken place for Harpy Eagles, building technical and biological basis for a successful restoration. Meanwhile, the habitat loss in Amazonia, combined with industrial logging and shooting by Amerindians and settlers, suggest that the species status must be reevaluated since Amazon Forest may no longer perform as a stronghold for the species in the future. We recommend researchers and practitioners to borrow from our discoveries regarding Harpy Eagle conservation.
Background: Spatio-temporal patterns of movement can characterize relationships between organisms and their surroundings, and address gaps in our understanding of species ecology, activity budgets, bioenergetics, and habitat resource management. Highly mobile waterfowl, which can exploit resources over large spatial extents, are excellent models to understand relationships between movements and resource usage, landscape interactions and specific habitat needs.
Methods: We tracked 3 species of dabbling ducks with GSM-GPS transmitters in 2015-17 to examine fine-scale movement patterns over 24 hour periods (30min interval), dividing movement pathways into temporally continuous segments and spatially contiguous patches. We quantified distances moved, area used and time allocated across the day, using linear and generalized linear mixed models. We investigated behavior through relationships between these variables.
Results: Movements and space-use were small, and varied by species, sex and season. Gadwall (Mareca strepera) generally moved least (FFDs: 0.5 – 0.7 km), but their larger foraging patches resulted from longer within-area movements. Pintails (Anas acuta) moved most, were more likely to conduct flights >300m, had FFDs of 0.8 – 1.1 km, used more segments and patches per day that they revisited more frequently, resulting in the longest daily total movements. Females and males differed only during the post-hunt season when females moved more. 23.6% of track segments were short duration (1-2 locations), approximately 1/3 more than would be expected if they occurred randomly, and were more dispersed in the landscape than longer segments. Distance moved in 30 minutes shortened as segment duration increased, likely reflecting phases of non-movement captured within segments.
Conclusions: Pacific Flyway ducks spend the majority of time using smaller foraging and resting areas than expected or previously reported, implying that foraging areas may be highly localized, and nutrients obtainable from smaller areas. Additionally, movement reductions over time demonstrates behavioral adjustments that represent divergent energetic demands, the detection of which is a key advantage of higher frequency data. Ducks likely use less energy for movement than currently predicted and management, including distribution and configuration of essential habitat, may require reconsideration. Our study illustrates how fine-scale movement data from tracking help understand and inform various other fields of research.
Many species depend on multiple habitats at different points in space and time. Their effective conservation requires an understanding of how and when each habitat is used, coupled with adequate protection. Migratory shorebirds use intertidal and supratidal wetlands, both of which are affected by coastal landscape change. Yet the extent to which shorebirds use artificial supratidal habitats, particularly at highly developed stopover sites, remains poorly understood leading to potential deficiencies in habitat management. We surveyed shorebirds on their southward migration in southern Jiangsu, a critical stopover region in the East Asian Australasian Flyway (EAAF), to measure their use of artificial supratidal habitats and assess linkages between intertidal and supratidal habitat use. To inform management, we examined how biophysical features influenced occupancy of supratidal habitats, and whether these habitats were used for roosting or foraging. We found that shorebirds at four of five sites were limited to artificial supratidal habitats at high tide for ~11–25 days per month because natural intertidal flats were completely covered by seawater. Within the supratidal landscape, at least 37 shorebird species aggregated on artificial wetlands, and shorebirds were more abundant on larger ponds with less water cover, less vegetation, at least one unvegetated bund, and fewer built structures nearby. Artificial supratidal habitats were rarely used for foraging and rarely occupied when intertidal flats were available, underscoring the complementarity between supratidal roosting habitat and intertidal foraging habitat. Joined‐up artificial supratidal management and natural intertidal habitat conservation are clearly required at our study site given the simultaneous dependence by over 35,000 migrating shorebirds on both habitats. Guided by observed patterns of habitat use, there is a clear opportunity to improve habitat condition by working with local land custodians to consider shorebird habitat requirements when managing supratidal ponds. This approach is likely applicable to shorebird sites throughout the EAAF. The dependence of thousands of imperiled migratory birds on artificial supratidal and natural intertidal wetlands necessitates simultaneous management of both habitats in coastal eastern China. Guided by observed patterns of use, there is a clear opportunity to improve habitat conditions by working with local land custodians to consider the habitat requirements of shorebirds when managing supratidal ponds that are used for human production activities.
Context: Many Australian mammal species are highly susceptible to predation by introduced domestic cats (Felis catus) and European red foxes (Vulpes vulpes). These predators have caused many extinctions and have driven large distributional and population declines for many more species. The serendipitous occurrence of, and deliberate translocations of mammals to, 'havens' (cat- A nd fox-free offshore islands, and mainland fenced exclosures capable of excluding cats and foxes) has helped avoid further extinction. Aims: The aim of this study was to conduct a stocktake of current island and fenced havens in Australia and assess the extent of their protection for threatened mammal taxa that are most susceptible to cat and fox predation. Methods: Information was collated from diverse sources to document (1) the locations of havens and (2) the occurrence of populations of predator-susceptible threatened mammals (naturally occurring or translocated) in those havens. The list of predator-susceptible taxa (67 taxa, 52 species) was based on consensus opinion from >25 mammal experts. Key results: Seventeen fenced and 101 island havens contain 188 populations of 38 predator-susceptible threatened mammal taxa (32 species). Island havens cover a larger cumulative area than fenced havens (2152 km² versus 346 km²), and reach larger sizes (largest island 325 km², with another island of 628 km² becoming available from 2018; largest fence: 123 km²). Islands and fenced havens contain similar numbers of taxa (27 each), because fenced havens usually contain more taxa per haven. Populations within fences are mostly translocated (43 of 49; 88%). Islands contain translocated populations (30 of 139; 22%); but also protect in situ (109) threatened mammal populations. Conclusions: Havens are used increasingly to safeguard threatened predator-susceptible mammals. However, 15 such taxa occur in only one or two havens, and 29 such taxa (43%) are not represented in any havens. The taxon at greatest risk of extinction from predation, and in greatest need of a haven, is the central rock-rat (Zyzomys pedunculatus). Implications: Future investment in havens should focus on locations that favour taxa with no (or low) existing haven representation. Although havens can be critical for avoiding extinctions in the short term, they cover a minute proportion of species' former ranges. Improved options for controlling the impacts of cats and foxes at landscape scales must be developed and implemented.
Conservation activities, including translocations of threatened species, are increasingly important priorities for conserving biodiversity and culture on Indigenous-managed lands, which occupy over 20% of the Australian landmass. In the Anangu Pitjantjatjara Yankunytjatjara (APY) Lands of north-western South Australia, the Warru Recovery Team reintroduced the threatened black-footed rock-wallaby (warru) to Wamitjara in May 2018. We outline the unique planning and logistical issues inherent in securing support and involvement of Traditional Owners and Indigenous rangers for predator, weed and fire management, cross-fostering, captive breeding, monitoring and translocation of the rock-wallabies. Altogether, the project cost AU3.86 million (actual-AU1.86 million, in kind-AU2.00 million) over 10 years of preparation and one year of post-Translocation monitoring. This consisted of AU1.18 million for cross-fostering and captive breeding at Monarto Zoo and a further AU0.55 million for the construction and maintenance of a fenced exclosure in the APY Lands. It is estimated that AU0.51 million of the total costs were directly attributed to working remote and Indigenous-owned land, with most of the remaining costs typical of other reintroduction programs. Large-scale reintroduction opportunities on Indigenous-managed land can provide considerable conservation outcomes as well as delivering cultural objectives and supporting employment.
Count data can be analyzed using generalized linear mixed models when observations are correlated in ways that require random effects. However, count data are often zero-inflated, containing more zeros than would be expected from the typical error distributions. We present a new package, glmmTMB, and compare it to other R packages that fit zero-inflated mixed models. The glmmTMB package fits many types of GLMMs and extensions, including models with continuously distributed responses, but here we focus on count responses. glmmTMB is faster than glmmADMB, MCMCglmm, and brms, and more flexible than INLA and mgcv for zero-inflated modeling. One unique feature of glmmTMB (among packages that fit zero-inflated mixed models) is its ability to estimate the Conway-Maxwell-Poisson distribution parameterized by the mean. Overall, its most appealing features for new users may be the combination of speed, flexibility, and its interface's similarity to lme4.
Background
Social learning allows animals to eavesdrop on ecologically relevant knowledge of competitors in their environment. This is especially important when selecting a habitat if individuals have relatively little personal information on habitat quality. It is known that birds can use both conspecific and heterospecific information for social learning, but little is known about the relative importance of each information type. If provided with the choice between them, we expected that animals should copy the behaviour of conspecifics, as these confer the best information for that species. We tested this hypothesis in the field for Pied Flycatchers Ficedula hypoleuca arriving at their breeding grounds to select a nest box for breeding. We assigned arbitrary symbols to nest boxes of breeding pied flycatchers (conspecifics) and blue and great tits, Cyanistes caeruleus and Parus major (heterospecifics), in 2014 and 2016 in two areas with different densities of tits and flycatchers. After ca 50% of flycatchers had returned and a flycatcher symbol was assigned to their nest box, we gave the later arriving flycatchers the choice between empty nest boxes with either a conspecific (flycatcher) or a heterospecific (tit) symbol.
Results
As expected, Pied Flycatchers copied the perceived nest box choice of conspecifics, but only in areas that were dominated by flycatchers. Against our initial expectation, flycatchers copied the perceived choice of heterospecifics in the area heavily dominated by tits, even though conspecific minority information was present.
Conclusions
Our results confirm that the relative density of conspecifics and heterospecifics modulates the propensity to copy or reject novel behavioural traits. By contrasting conspecific and heterospecific ecology in the same study design we were able to draw more general conclusions about the role of fluctuating densities on social information use.
Search behavior is often used as a proxy for foraging effort within studies of animal movement, despite it being only one part of the foraging process, which also includes prey capture. While methods for validating prey capture exist, many studies rely solely on behavioral annotation of animal movement data to identify search and infer prey capture attempts. However, the degree to which search correlates with prey capture is largely untested. This study applied seven behavioral annotation methods to identify search behavior from GPS tracks of northern gannets (Morus bassanus), and compared outputs to the occurrence of dives recorded by simultaneously deployed time–depth recorders. We tested how behavioral annotation methods vary in their ability to identify search behavior leading to dive events. There was considerable variation in the number of dives occurring within search areas across methods. Hidden Markov models proved to be the most successful, with 81% of all dives occurring within areas identified as search. k-Means clustering and first passage time had the highest rates of dives occurring outside identified search behavior. First passage time and hidden Markov models had the lowest rates of false positives, identifying fewer search areas with no dives. All behavioral annotation methods had advantages and drawbacks in terms of the complexity of analysis and ability to reflect prey capture events while minimizing the number of false positives and false negatives. We used these results, with consideration of analytical difficulty, to provide advice on the most appropriate methods for use where prey capture behavior is not available. This study highlights a need to critically assess and carefully choose a behavioral annotation method suitable for the research question being addressed, or resulting species management frameworks established.
Translocations are a valuable tool within conservation, and when performed successfully can rescue species from extinction. However, to label a translocation a success, extensive post-translocation monitoring is required, ensuring the population is growing at the expected rate. In 2011, a habitat assessment identified Frégate Island as a suitable island to host a Seychelles Warbler (Acrocephalus sechellensis) population. Later that year, 59 birds were translocated from Cousin Island to Frégate Island. Here, we determine Seychelles Warbler habitat use and population growth on Frégate Island, assessing the status of the translocation and identifying any interventions that may be required. We found that territory quality, an important predictor of fledgling production on Cousin Island, was a poor predictor of bird presence on Frégate Island. Instead, tree diversity, middle-storey vegetation density, and broad-leafed vegetation density all predicted bird presence positively. A habitat suitability map based on these results suggests most of Frégate Island contains either a suitable or a moderately suitable habitat, with patches of unsuitable overgrown coconut plantation. To achieve the maximum potential Seychelles Warbler population size on Frégate Island, we recommend habitat regeneration, such that the highly diverse subset of broad-leafed trees and a dense middle storey should be protected and replace the unsuitable coconut. Frégate Island’s Seychelles Warbler population has grown to 141 birds since the release, the slowest growth rate of all Seychelles Warbler translocations; the cause of this is unclear. This study highlights the value of post-translocation monitoring, identifying habitat use and areas requiring restoration, and ultimately ensuring that the population is growing.
Supplementary feeding is a common practice to raise reproductive output in raptors and other species; nevertheless, its application in conservation has only recently been discussed critically. Here, we analyse the effect of supplementary feeding in territorial raptors, taking advantage of two long-term datasets for the Spanish imperial eagle (Aquila adalberti) and bearded vulture (Gypaetus barbatus). In both species, supplementary feeding was used over four years, allowing the extraction of eggs or nestlings for reintroduction programmes. Both populations increased during the last 20 years. In 2001, only 10 Spanish imperial eagle pairs were found in Sierra Morena, increasing to 91 pairs in 2015 (810% of increase). The Bearded vulture population in Aragon increased from 15 occupied territories in 1988 to 67 in 2012 (347% of increase). Density-dependent breeding productivity on habitat heterogeneity was established in both populations. Results of generalized linear mixed model analysis with relative productivity as the dependent variable, species and supplementary feeding as fixed factors, and territory as random factor showed a significant effect of supplementary feeding on relative productivity in both species as well as in the interaction between territory and supplementary feeding. This implied a different response among territories to supplementary feeding. Birds in poor-quality territories with low productivity levels responded more strongly to supplementary feeding than birds in territories with higher levels of natural productivity. A reintroduction programme based on supplementary feeding and extraction of nestlings costs eight times less than the same programme based on captive breeding and takes 10 years less. Synthesis and applications. Supplementary feeding in territorial raptors could be useful (1) in an episodic main prey collapse and (2) in poor-quality territories in a high-density population, to produce extra young for reintroduction programmes. For greatest efficiency, supplementary feeding needs to be targeted at poorer territories in which the reproductive rate has the potential to be raised by provision of extra food. The extra young produced can then be used in reintroduction programmes in which chances of recruiting to a breeding population are high.
Potential for habitat restoration is increasingly used as an argument for reintroducing ecosystem engineers. Beaver have well known effects on hydromorphology through dam construction, but their scope to restore wetland biodiversity in areas degraded by agriculture is largely inferred. Our study presents the first formal monitoring of a planned beaver-assisted restoration, focussing on changes in vegetation over 12years within an agriculturally-degraded fen following beaver release, based on repeated sampling of fixed plots. Effects are compared to ungrazed exclosures which allowed the wider influence of waterlogging to be separated from disturbance through tree felling and herbivory. After 12years of beaver presence mean plant species richness had increased on average by 46% per plot, whilst the cumulative number of species recorded increased on average by 148%. Heterogeneity, measured by dissimilarity of plot composition, increased on average by 71%. Plants associated with high moisture and light conditions increased significantly in coverage, whereas species indicative of high nitrogen decreased. Areas exposed to both grazing and waterlogging generally showed the most pronounced change in composition, with effects of grazing seemingly additive, but secondary, to those of waterlogging. Our study illustrates that a well-known ecosystem engineer, the beaver, can with time transform agricultural land into a comparatively species-rich and heterogeneous wetland environment, thus meeting common restoration objectives. This offers a passive but innovative solution to the problems of wetland habitat loss that complements the value of beavers for water or sediment storage and flow attenuation. The role of larger herbivores has been significantly overlooked in our understanding of freshwater ecosystem function; the use of such species may yet emerge as the missing ingredient in successful restoration.
Investigating habitat use and preferences of a threatened species can be challenging, especially if wild populations have decreased to such low numbers that they occupy only fractions of their former natural range. Hence, assessing habitat suitability of a potential release site for a threatened species before a reintroduction attempt can be difficult because frequently no comparable baseline data are available. In these instances, post-release monitoring data can inform about habitat use and preferences of a reintroduced species. Here, we use monitoring data of an endangered endemic island bird, the Chatham Island black robin Petroica traversi, to investigate habitat preferences and the temporal change in distribution patterns across 26 years following a reintroduction. We show that densities and distribution of black robin pairs at the reintroduction site have changed significantly over the years. Spatial distribution of pairs is clustered, and this clustering has intensified as the population increased. We used the maximum entropy method MaxEnt to model habitat suitability on the island, showing that black robins clearly prefer forested areas inland that are within 70 m to the forest edge at lower elevations (<40 m a.s.l.) and on slopes that have a N-NE aspect. The model also identified one area on the island that comprises suitable habitat, but is currently uninhabited. Applying maximum observed densities to the available area of each suitability class, carrying capacity is estimated as 170 nesting pairs across the island, highlighting the need to find further appropriate habitat urgently. Overall, these topographical and habitat preferences considerably restrict this species' potential distribution, a constraint that has serious conservation implications for future population growth of current populations and (re)introductions to new locations. This study demonstrates that post-release data can reveal relevant limitations to habitat use of highly threatened species.
The availability of spatially referenced environmental data and species occurrence records in online databases enable practitioners to easily generate species distribution models (SDMs) for a broad array of taxa. Such databases often include occurrence records of unknown reliability, yet little information is available on the influence of data quality on SDMs generated for rare, elusive, and cryptic species that are prone to misidentification in the field. We investigated this question for the fisher (Pekania pennanti), a forest carnivore of conservation concern in the Pacific States that is often confused with the more common Pacific marten (Martes caurina). Fisher occurrence records supported by physical evidence (verifiable records) were available from a limited area, whereas occurrence records of unknown quality (unscreened records) were available from throughout the fisher’s historical range. We reserved 20% of the verifiable records to use as a test sample for both models and generated SDMs with each dataset using Maxent. The verifiable model performed substantially better than the unscreened model based on multiple metrics including AUCtest values (0.78 and 0.62, respectively), evaluation of training and test gains, and statistical tests of how well each model predicted test localities. In addition, the verifiable model was consistent with our knowledge of the fisher’s habitat relations and potential distribution, whereas the unscreened model indicated a much broader area of high-quality habitat (indices > 0.5) that included large expanses of high-elevation habitat that fishers do not occupy. Because Pacific martens remain relatively common in upper elevation habitats in the Cascade Range and Sierra Nevada, the SDM based on unscreened records likely reflects primarily a conflation of marten and fisher habitat. Consequently, accurate identifications are far more important than the spatial extent of occurrence records for generating reliable SDMs for the fisher in this region. We strongly recommend that practitioners avoid using anecdotal occurrence records to build SDMs but, if such data are used, the validity of resulting models should be tested with verifiable occurrence records.
Soil microbial communities are often overlooked in the context of ecological restoration. Given their central role in a broad range of ecosystem processes, however, understanding their response to restoration activities is critical to predicting restoration trajectories. In this study, we quantified the response of soil bacterial and fungal communities to restoration treatments, variation in microhabitat elements and vegetation in a critically endangered Australian box-gum grassy woodland ecosystem. Restoration treatments included the addition of coarse woody debris (CWD) and reduced grazing pressure. Four years after applying restoration treatments, we found no significant effect of CWD addition on soil microbial diversity, while reduced grazing significantly affected composition of the fungal, but not the bacterial, communities. Both bacterial and fungal communities responded to microhabitat element (open ground vs. old logs and trees), overlying vegetation and soil edaphic properties, and strong aboveground-belowground linkages were observed. Plant alpha diversity was positively correlated to soil bacterial, but not fungal, alpha diversity and plant community composition was a good predictor of both soil bacterial and fungal beta diversity. Co-occurrence network analysis identified numerous complex, non-linear associations between soil bacteria, fungi, edaphic properties and overlying plants. Soil microbes affected by restoration treatments included fungal saprotrophs and Actinobacteria, likely involved in litter breakdown, as well as bacteria likely involved in soil N cycling. Although the directions of the observed plant-microbe relationships remain unclear, we demonstrated the possibility of inducing changes to soil microbial communities to enhance restoration outcomes in box-gum grassy woodland ecosystems.
Reintroductions have been increasingly used for species restoration and it seems that this conservation tool is going to be more used in the future. Nevertheless, there is not a clear consensus about the better procedure for that, consequently a better knowledge of how to optimize this kind of management is needed. Here we examined the dynamics of released long-lived bird populations (lesser kestrel, Falco naumanni, Bonelli's eagle Aquila fasciata, and bearded vulture Gypaetus barbatus) in object-oriented simulated reintroduction programs. To do that, number of young per year and number of years of released necessary to achieve a successful reintroduced population were calculated. We define a successful reintroduction as one in which when the probability of extinction during two times the maximum live-span period for the species (20, 50, and 64 years respectively) was less than 0.001 (p<0.001) and they showed a positive trend in population size (r>0.00). Results showed that a similar total number of young (mean 98.33-5.26) must be released in all the species in all the scenarios in order to get a successful reintroduction. Consequently, as more young per year are released the new population is going to be larger at the end of the simulations, the lesser the negative effects in the donor population and the lowest the total budget needed will be. © 2017 Morandini, Ferrer. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abstract
The management of populations of threatened species requires the capacity to identify areas of high habitat
value. We developed a high resolution species distribution model (SDM) for the endangered Pilbara
northern quoll Dasyurus hallucatus, population using MaxEnt software and a combined suite of bioclimatic
and landscape variables. Once common throughout much of northern Australia, this marsupial
carnivore has recently declined throughout much of its former range and is listed as endangered by the
IUCN. Other than the potential threats presented by climate change, and the invasive cane toad Rhinella
marina (which has not yet arrived in the Pilbara). The Pilbara population is also impacted by introduced
predators, pastoral and mining activities. To account for sample bias resulting from targeted surveys unevenly
spread through the region, a pseudo-absence bias layer was developed from presence records of
other critical weight-range non-volant mammals. The resulting model was then tested using the biomod2
package which produces ensemble models from individual models created with different algorithms. This
ensemble model supported the distribution determined by the bias compensated MaxEnt model with a
covariance of of 86% between models with both models largely identifying the same areas as high priority
habitat. The primary product of this exercise is a high resolution SDM which corroborates and elaborates
on our understanding of the ecology and habitat preferences of the Pilbara Northern Quoll population
thereby improving our capacity to manage this population in the face of future threats.
Nature Conservation 18: 27–46 (2017)
doi: 10.3897/natureconservation.18.12235
http://natureconservation.pensoft.net
Copyright
Wherever wildlife management concerns the movement of individuals across structured habitat, its scale of operations will encompass metapopulation dynamics. The goal of this chapter is to review the potential applications of metapopulation concepts and models in reserve design and conservation management. Our perspective is forward-looking. We show how some key problems of where to direct conservation effort and how to manage populations can be addressed in the context of regional habitat structure and the survival and renewal of habitat patches. We also mention several cases of successful metapopulation management and point out practical problems. We emphasise (1) that the viability of a population may depend on surrounding populations, in which case metapopulation processes influence or determine reserve design and management options; (2) that understanding the dynamic processes requires models, which make assumptions that need validating; (3) that the principle limitation of metapopulation models is their single-species focus. Conservation strategies clearly depend on the particular social, economic and ecological circumstances of each region, and concepts such as the metapopulation can seem irrelevant to practical concerns. We aim to show, nevertheless, that an understanding of metapopulation dynamics can be vital to asking pertinent questions and seeking potential solutions. The conceptual framework of metapopulation dynamics tells us what information is needed in order to build case-specific models relevant to any of a wide range of issues. These issues include the potential disadvantages of habitat corridors, or hidden benefits of sink habitat; the optimal schedule for translocations or reintroductions; the relative merits of reducing local extinctions against increasing colonisations; the optimum distribution of habitat improvement; and the advantages of increasing life spans of ephemeral habitats.
For migratory species, the success of population reintroduction or reinforcement through captive-bred released individuals depends on survivors undertaking appropriate migrations. We assess whether captive-bred Asian Houbara Chlamydotis macqueenii from a breeding programme established with locally sourced individuals and released into suitable habitat during spring or summer undertake similar migrations to wild birds. Using satellite telemetry, we compare the migrations of 29 captive bred juveniles, 10 wild juveniles and 39 wild adults (including three birds first tracked as juveniles), examining migratory propensity (proportion migrating), timing, direction, stopover duration and frequency, efficiency (route deviation) and wintering and breeding season locations. CAPTIVE BRED birds initiated autumn migration an average of 20.6 (± 4.6) days later and wintered 470.8 km (± 76.4) closer to the breeding grounds, mainly in Turkmenistan, northern Iran and Afghanistan, than wild birds, which migrated 1217.8 km (± 76.4), predominantly wintering in southern Iran and Pakistan (juveniles and adults were similar). Wintering locations of four surviving captive bred birds were reoccupied in subsequent years (median distance to first wintering site = 70.8 km, range 6.56–221.6 km), suggesting that individual captive bred birds (but not necessarily their progeny) remain faithful to their first wintering latitude. The migratory performance of captive bred birds was otherwise similar to that of wild juveniles. Although the long-term fitness consequences for captive bred birds establishing wintering sites at the northern edge of those occupied by wild birds remain to be quantified, it is clear that the pattern of wild migrations established by long-term selection is not replicated. If the shorter migration distance of young captive bred birds has a physiological rather than a genetic basis, then their progeny may still exhibit wild-type migration. However, as there is a considerable genetic component to migration, captive breeding management must respect migratory population structure as well as natal and release-site fidelity.
Conservation behavior assists the investigation of species endangerment associated with managing animals impacted by anthropogenic activities. It employs a theoretical framework that examines the mechanisms, development, function, and phylogeny of behavior variation in order to develop practical tools for preventing biodiversity loss and extinction. Developed from a symposium held at the International Congress on Conservation Biology in 2011, this is the first book to offer an in-depth, logical framework that identifies three vital areas for understanding conservation behavior: anthropogenic threats to wildlife, conservation and management protocols, and indicators of anthropogenic threats. Bridging the gap between behavioral ecology and conservation biology, this volume ascertains key links between the fields, explores the theoretical foundations of these linkages, and connects them to practical wildlife management tools and concise applicable advice. Adopting a clear and structured approach throughout, this book is a vital resource for graduate students, academic researchers, and wildlife managers.
This book (11 chapters) presents an overview of seed ecophysiology and its role in shaping plant communities. Updated information on frugivory, seed dispersal, seed predation, light-mediated germination responses, chemical regulation of germination, and seed dormancy is provided. New chapter contributions include an overview of seed development, anatomy and morphology, the chemical ecology of seed persistence, implications of climate change on the regeneration by seeds, and the functional role of seed banks in agricultural and natural ecosystems. This book serves as a highly comprehensive review resource for new students of seed ecology and plant community regeneration, as well as an update for the more seasoned and experienced scientist.
A ‘refugee’ species is one with a current distribution that has been restricted to a subset of their former niche by threatening processes. Conservation opportunities for such species can be limited by a poor understanding of habitat requirements, where habitat models are based on current distributions and not the innate capacity of the animal to survive where threats are managed. We examined patterns of habitat selection by a putative refugee species, the threatened New Holland mouse Pseudomys novaehollandiae, following reintroduction into historic habitat (habitat that corresponds to a currently unoccupied component of its former niche). Current New Holland mouse populations exist predominantly in coastal heath habitat of select vegetation and fire history, and these environmental conditions differ greatly to those found across the species historical distribution. Using a novel, non‐invasive method of detection for the species, we investigated patterns of habitat selection following reintroduction into historic habitat, where the species primary threat of exotic predators has been removed. We also assessed the changes in genetic diversity measures across three stages of the reintroduction process (before, during and after) using microsatellite markers, to reflect on past efforts in maintaining genetic diversity. We found that historic habitat can still support New Holland mouse populations and identified more diverse potential habitat for the species. We also identified loss of alleles and an increased inbreeding coefficient at the captive breeding stage, but these findings were not statistically significant. This study expands on our limited understanding of habitat requirements and the fundamental niche of the New Holland mouse, highlighting new potential conservation opportunities. Many small Australian native mammals currently reside in refuge habitat. Habitat models for these species are typically based on current distributions and not on the innate capacity of the animal to survive where introduced threats are managed. Thus, our understanding of the fundamental ecology of these species is relatively poor. We used a novel non‐invasive survey technique to investigate habitat use by the New Holland mouse post reintroduction into ‘historic habitat’, where exotic predators have been removed. We also investigated changes in genetic diversity measures throughout the reintroduction process, to reflect on past methods in maintaining genetic diversity and inform future management strategies. This study expands on our limited understanding of the fundamental ecology of the New Holland mouse, highlighting new potential conservation opportunities.
Many translocations and introductions to recover threatened populations fail because predators kill prey soon after release; a problem exacerbated for predator-naive prey. While pre-release training has been shown to work in some situations, it is time consuming and relies on using inferred predator cues and treating small groups. We review a relatively new and very promising management tool: in situ , pre-release predator conditioning. Here, the goal is to allow prey in large enclosures to live with low densities of predators to accelerate selection for antipredator traits (in an evolutionary sense) or provide prey essential experience with predators that they will later encounter. We review the published results of a large-scale, controlled experiment where we have permitted burrowing bettongs ( Bettongia lesueur ) and greater bilblies ( Macrotis lagotis ) to live with low densities of feral cats ( Felis catus ), a species implicated in their widespread decline and localized extinction. We found that both species could persist with cats, suggesting that future work should define coexistence thresholds—which will require knowledge of prey behaviour as well as the structure of the ecological community. Compared to control populations, predator-naive prey exposed to cats has a suite of morphological and behavioural responses that seemingly have increased their antipredator abilities. Results suggest that predator-conditioned bilbies survive better when released into a large enclosure with an established cat population; future work will determine whether this increased survival extends to the wild.
This article is part of the theme issue ‘Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation’.
Spillover effects are an expansion of conservation benefits beyond protected areas through dispersal of species that reside within. They have been well documented in marine but not terrestrial systems. To understand the effects on wildlife created by conservation fences, we explored the internal and external gradients of activity in mammal, reptile, and bird species at a conservation reserve in arid Australia that is fenced to exclude invasive rabbits (Oryctolagus cuniculus), cats (Felis catus), and foxes (Vulpes vulpes). Two methods were used: counts of animal tracks along transects on sand dunes and captures at pitfall‐trapping sites. In both cases, sites were spaced at different distances from the reserve fenceline inside and outside the reserve. We recorded a range of spillover, source‐sink, step, and barrier effects that combined to create a zone within and around the reserve with fence‐induced species‐specific wildlife gradients. Two endemic rodents but none of the 4 mammal species reintroduced to the reserve showed positive spillover effects. Barrier effects, where activity was highest close to the fence, were recorded for the feral cat and native bettong (Bettongia lesueur), species that could not breach the fence. In comparison, some reptiles and native mammal species that could permeate the fence displayed source‐sink effects; that is, their activity levels were reduced close to the fence likely due to constant emigration to the side with lower density. Activity of some reptiles was lowest at core sites in the reserve and increased as distance toward the outside increased, a gradient likely related to trophic cascades triggered by predator exclusion. Our result show that fenced reserves can create overlapping layers of species‐specific gradients related to each species’ ability to permeate the fence and its varying susceptibility to threats. Managers should be aware that these gradients may extend for several kilometers either side of the fence and that not all contained species will increase in abundance. Creating wider conservation benefits may require increased fence permeability and threat reduction outside the fence. This article is protected by copyright. All rights reserved Article impact statement: Conservation fences create species‐specific internal and external wildlife gradients that don't always generate positive conservation benefits.
The eastern bettong (Bettongia gaimardi), a medium-sized digging marsupial, was reintroduced to a predator-free reserve after 100 years of absence from the Australian mainland. The bettong may have the potential to restore temperate woodlands degraded by a history of livestock grazing, by creating numerous small disturbances by digging. We investigated the digging capacity of the bettong and compared this to extant fauna, to answer the first key question of whether this species could be considered an ecosystem engineer, and ultimately if it has the capacity to restore lost ecological processes. We found that eastern bettongs were frequent diggers and, at a density of 0.3-0.4 animals ha-1, accounted for over half the total foraging pits observed (55%), with echidnas (Tachyglossus aculeatus), birds and feral rabbits (Oryctolagus cuniculus) accounting for the rest. We estimated that the population of bettongs present dug 985 kg of soil per ha per year in our study area. Bettongs dug more where available phosphorus was higher, where there was greater basal area of Acacia spp. and where kangaroo grazing was less. There was no effect on digging of eucalypt stem density or volume of logs on the ground. While bettong digging activity was more frequent under trees, digging also occurred in open grassland, and bettongs were the only species observed to dig in scalds (areas where topsoil has eroded to the B Horizon). These results highlight the potential for bettongs to enhance soil processes in a way not demonstrated by the existing fauna (native birds and echidna), and introduced rabbit.
Wildlife translocations can have conservation value but results have been mixed regarding animal behavior and survival post-release. Practitioners have adopted antipredator training, environmental enrichment, and soft release as pre-release conditioning tactics to encourage adaptive behavior and improve post-release survival, but their utility has not been broadly quantified. We performed a formal literature review and conducted meta-analysis on 108 effects from 41 studies experimentally testing how these tactics affected survival, movement, or site fidelity compared to unconditioned animals. We further investigated how each conditioning tactic, animal source (wild-to-wild translocated or captive-released), age, and taxonomic group (birds, fish, mammals, and reptiles) influenced outcomes. Relative to unconditioned animals, conditioned individuals were 1.5 times more likely to survive, had reduced movement, and were three times more likely to show site fidelity. Each of the three conditioning tactics resulted in improved survival. Juveniles released from captivity derived the greatest survival benefit from conditioning. Across taxa, conditioning most benefitted survival of fish. Conditioning also had positive effects on survival of mammals and reptiles, albeit with less certainty than for fish. Estimates comparing survival of conditioned to unconditioned birds were much more variable, suggesting avian translocation programs using conditioning generally need improvement. Soft release consistently reduced movement and increased site fidelity; this was an especially viable technique for adult wild-to-wild translocated animals. We provide quantitative evidence that behavioral conditioning can aid wildlife translocations, and we encourage continued experiments to further elucidate how refined tactics could advance conservation efforts using translocation as a management tool.
Conservation translocations of threatened species are being widely used to mitigate human impacts. However, their effects are surrounded by some controversy since these actions have often failed to meet planned objectives. Despite the limited number of published studies, existing evidence indicates that a main constraint for the long-term success of translocation actions is the selection of suitable receptor sites. In this study, we present a methodological approach to identify suitable receptor sites that combines the use of species distribution models (SDMs) and in situ field validation trials. This method was successfully applied to translocate a population of Critically Endangered Narcissus cavanillesii, which was going to be destroyed by the construction of the Alqueva dam (Portugal), the largest dam in Europe. The results of the SDM developed for the target species were biologically validated through in situ germination trials in sites with contrasting species suitability values. The population translocated to the site selected with this approach has experienced a stable demographic trend for more than ten years and established new mature plants outside the translocated patches. This methodology, which has proven to be a fast and reliable approach for the selection of appropriate receptor sites for conservation translocations, could be useful in other studies. Keywords: Extinction, Receptor site selection, Conservation translocations, Narcissus cavanillesii, Portugal
The Action Plan for Australian Birds 2010 is the third in a series of action plans that have been produced at the start of each decade. The book analyses the International Union for Conservation of Nature (IUCN) status of all the species and subspecies of Australia's birds, including those of the offshore territories. For each bird the size and trend in their population and distribution has been analysed using the latest iteration of IUCN Red List Criteria to determine their risk of extinction. The book also provides an account of all those species and subspecies that are or are likely to be extinct. The result is the most authoritative account yet of the status of Australia's birds. In this completely revised edition each account covers not only the 2010 status but provides a retrospective assessment of the status in 1990 and 2000 based on current knowledge, taxonomic revisions and changes to the IUCN criteria, and then reasons why the status of some taxa has changed over the last two decades. Maps have been created specifically for the Action Plan based on vetted data drawn from the records of Birds Australia, its members and its partners in many government departments. This is not a book of lost causes. It is a call for action to keep the extraordinary biodiversity we have inherited and pass the legacy to our children. 2012 Whitley Award Commendation for Zoological Resource.
Long-term monitoring of threatened species often reveals processes undermining population recovery that may not be evident over shorter timeframes. When populations are small and isolated, normal behaviours such as dispersal may cause the loss of certain demographic stages if compensatory immigration no longer occurs. Social interactions that facilitate mate pairing can become rare,
reducing the likelihood of successful breeding pairs establishing. Against a backdrop of habitat loss and degradation, these factors may make population recovery difficult to achieve. We present 15
years of monitoring data from the Central Coast of NSW targeting a small population of endangered Bush Stone-curlews Burhinus grallarius. The monitoring, undertaken by volunteers, collected breeding and banding observations between 2003 and 2018. Taken together, the data show that the number of breeding pairs fluctuates between 1 and 6, and can increase relatively quickly. However, juvenile dispersal south to highly urbanised and dangerous sites in Sydney has become a population ‘sink’, undermining population recovery. The long-term banding observations have been fundamental to understanding
how juvenile dispersal affects Bush Stone-curlew population dynamics. We suggest translocating pairs to ‘stepping stone’ sites to the north of the population to exploit dispersal behaviours and enhance connectivity between the Central Coast population and breeding pairs around Port Stephens. We strongly urge the continuation of monitoring in conjunction with local habitat conservation and management to work towards sustainable and resilient Bush Stone-curlew populations.
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.
Context. Reintroductions can be an effective means of re-establishing locally extinct or declining faunal populations. However, incomplete knowledge of variables influencing survival and establishment can limit successful outcomes. Aim. We aimed to examine the factors (e.g. sex, body mass, release order) influencing the survival, dispersal, home range and habitat selection of reintroduced southern brown bandicoots (eastern subspecies; Isoodon obesulus obesulus) into an unfenced, predator-managed environment in south-eastern Australia (Booderee National Park). Methods. Over 2 weeks in May 2016, six female and five male bandicoots were wild-caught in state forest and hard released into the park. Release locations were approximately evenly distributed between three primary vegetation types assessed as suitable habitat: heath, woodland and forest. Bandicoots were radio-tracked day and night for 4 weeks from the initial release date. Key results. No mortality was detected. Males dispersed more than twice as far as females (male x 704 m, female x 332 m), but there was no significant sex bias in home range size. At the landscape scale, bandicoots preferentially selected home ranges that contained heath and avoided forest. Within home ranges, heath and woodland were both favoured over forest. Conclusions. Post-release dispersal is sex-biased, but more data are required to determine the influence of other predictors such as body mass and release order. Within the release area, bandicoots favoured non-forest vegetation types. Implications. Our study outlines factors influencing the establishment of reintroduced bandicoots. We recommend that future bandicoot reintroductions to Booderee National Park occur within areas of heath and woodland, and that subsequent releases consider the potentially larger spatial requirements and conspecific avoidance among male bandicoots. Our findings contribute new knowledge for improving translocation methods of a nationally endangered mediumsized mammal.
The keystone species concept was introduced in 1969 in reference to top-down regulation of communities by predators, but has expanded to include myriad species at different trophic levels. Keystone species play disproportionately large, important roles in their ecosystems, but human-wildlife conflicts often drive population declines. Population declines have resulted in the necessity of keystone species reintroduction, however, studies of such reintroductions are rare. We conducted a literature review and found only 30 peer-reviewed journal articles that assessed reintroduced populations of keystone species, and only 11 of these assessed ecosystem-level effects following reintroduction. Nine of 11 publications assessing ecosystem-level effects found evidence of resumption of keystone roles; however, these publications focus on a narrow range of species. We highlight the deficit of peer-reviewed literature on keystone species reintroductions, and draw attention to the need for assessment of ecosystem-level effects so that the presence, extent, and rate of ecosystem restoration driven by keystone species can be better understood.
Large areas of habitat are being fenced globally to restore and relocate species that can no longer survive in their surrounding landscapes, such as because of introduced predators. Despite their promise, the contributions of fenced and intensively-managed reserves towards achieving wider biodiversity goals are contentious. There has been little empirical evidence that fenced reserves can restore communities or ecological function over larger landscapes in ways that justify their large economic and sometimes social costs. Here we tested whether the exclusion of introduced predators restored mammal-sensitive habitat after 8 years within a mainland fenced reserve in southern New Zealand. We also asked whether the abundance of bird-dispersed fruiting trees and frugivorous birds was elevated immediately outside the reserve as compared with the broader landscape. We found that only saplings of fleshy-fruited tree species sensitive to browsing and seed predation by introduced mammals increased over time within the reserve. These mammal-sensitive trees were also more abundant in the surrounding unfenced landscape when close to the reserve, i.e. within 500 m. Our results suggested that mammal-sensitive trees were benefitting from increased fruit dispersal that was spilling over the fenced boundary as mammal-sensitive frugivores responded to predator control. Using point count surveys at 278 unique sites throughout the broader region, we found that the native frugivore community that evolved in the absence of mammalian predators was a third more abundant within the reserve and immediately outside the fenced boundary than at sites 20 km away in the surrounding landscape. Non-endemic frugivores did not show the same spatial pattern. Our work provides among the first evidence that an intensively-managed wildlife reserve can measurably restore populations of threatened flora and fauna and disperse conservation benefits into wider landscapes.
Translocations are an important conservation tool, but many are unsuccessful. Soft-release translocations involve holding animals on site for a period prior to release, whereas hard-release translocations involve immediate release of animals into a new environment. Evaluating the relative impacts of hard and soft release on site fidelity of released individuals can be informative, especially when comparing between translocated and resident animals. We monitored the movement, dispersal, and home range of both translocated (hard and soft released) and resident Jewelled Geckos (Naultinus gemmeus) for three weeks during winter using radiotelemetry. We also monitored a hard-released group during summer and incorporated data from a previously published soft- versus hard-release translocation of Jewelled Geckos undertaken in spring. In winter, soft-released geckos dispersed less than hard-released geckos and both soft-released and resident geckos had significantly smaller home ranges than those hard released. Further, area occupied by soft-released geckos remained constant during the tracking period but increased 20-fold for hard-released geckos. Mean dispersal distances were not influenced by season or the amount of time in an enclosure prior to soft release (i.e., four months yielded similar results to nine months). Translocations employing a soft-release strategy may have value for a wide range of lizard species and could contribute to translocation success.
Reintroduction biology is a field of scientific research that aims to inform translocations of endangered species. We review two decades of published literature to evaluate whether reintroduction science is evolving in its decision-support role, as called for by advocates of evidence-based conservation. Reintroduction research increasingly addresses a priori hypotheses, but remains largely focused on short-term population establishment. Similarly, studies that directly assist decisions by explicitly comparing alternative management actions remain a minority. A small set of case studies demonstrate full integration of research in the reintroduction decision process. We encourage the use of tools that embed research in decision-making, particularly the explicit consideration of multiple management alternatives because this is the crux of any management decisions.
In the last two decades it has become increasingly clear that the spatial dimension is a critically important aspect of ecological dynamics. Ecologists are currently investing an enormous amount of effort in quantifying movement patterns of organisms. Connecting these data to general issues in metapopulation biology and landscape ecology, as well as to applied questions in conservation and natural resource management, however, has proved to be a non-trivial task. This book presents a systematic exposition of quantitative methods for analyzing and modeling movements of organisms in the field. Quantitative Analysis of Movement is intended for graduate students and researchers interested in spatial ecology, including applications to conservation, pest control, and fisheries. Models are a key ingredient in the analytical approaches developed in the book; however, the primary focus is not on mathematical methods, but on connections between models and data. The methodological approaches discussed in the book will be useful to ecologists working with all taxonomic groups. Case studies have been selected from a wide variety of organisms, including plants (seed dispersal, spatial spread of clonal plants), insects, and vertebrates (primarily, fish, birds, and mammals).
