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Context. The lack of documentation and detailed assessment of previous sun bear (Helarctos malayanus) release programs raises concerns about bears’ capacity to adapt to their new habitats and key elements of release success.
AimsWe evaluated the influence of the sun bears’ individual profiles and environmental factors on their adaptability, and investigated their habitat use and movements in the wild.
Methods. We released 13 rescued sun bears (four wild-caught and nine rehabilitated) to natural habitats between December 2015 and August 2017, and inferred adaptability process by analysing their pre- and post-release data.
Key results. Post-release monitoring showed that sun bears required at least a month to acclimatise to their release area. No nuisance cases were reported, and bears were observed avoiding monitoring teams in a series of encounters. Principal-component analysis identified a previous history of ill health (e.g. malnutrition), low avoidance of humans prior to release and low potential of release sites as significant factors associated with poor adaptability of released bears. Rehabilitated bears also showed lower adaptability to hilly topography with an average elevation of more than 500 m. Individual profiles of adult physically fit wild-caught bears with high avoidance of humans prior to release were associated with high adaptability. Binary logistic regression indicated that habitat type was the main factor influencing bear movement. Bears had a high affinity for oil palm plantations adjacent to the forest edge. Most habitat use of released bears was close to the forest edge.
Conclusions. In terms of competition, predation, food availability, and adaptability, the selection of forest edges adjacent to other favourable habitats is perceived as a more opportunistic survival strategy, as long as the bears do not rely on humans to survive and endure with the natural interactions in the wild.
Implications. This study emphasises the importance of improving the likelihood of survival of rehabilitated bears, especially in the early release phase. Reducing human–bear interaction in rehabilitation centres by practising a buddy system and minimal human contact in captivity considerably enhances release effectiveness.
Context. Sex and age are frequently proposed as drivers of a number of behavioural and demographic patterns that can have important consequences for population dynamics including access to mates, sexual selection, parental care and lifetime productivity. Sex and age might also be important in shaping the movement patterns and colonisation processes of social species moving into vacant habitat. Such information is critical for the management of strongly interacting species such as the noisy miner (Manorina melanocephala), which structure ecological communities through aggressive exclusion of other taxa from areas that they occupy.
Aims. In Manorina colonies, young females are usually dispersive, while males remain in the natal colony as the philopatric sex. Following removal of individuals from an area, we aimed to determine whether female-biased dispersal, particularly of young females, would result in a more equal sex ratio and a younger age structure in the recolonising population.
Methods. These predictions were tested by anatomically ageing and sexing 1856 noisy miners that had been experimentally culled in two regions of New South Wales, Australia, to reduce the aggressive impact of this species on other native species.
Key results. Prior to removal, noisy miner populations were significantly male-biased in both regions (57% and 60%); however sex ratios after each of two removal episodes no longer differed from parity. Immature birds were a dominant feature (65%) of recolonising populations in both regions, however, the age structure of recolonising populations was different in each region, mostly likely due to the respective timing of culls during the year. Furthermore, the culling response in terms of age-specific sex ratio varied between regions. After the final cull, the sex ratio of mature birds had fallen to parity in one region but had become even more male biased (68%) in the other region. There was no sex-ratio bias among immature birds before or after culling.
Conclusion. These results confirm the expectation that immature birds are more likely to be colonisers, but the expectation of greater female dispersal was equivocal.
Implications. The differences in response between regions may reflect variation in population density, landscape connectivity or seasonality, highlighting challenges when implementing culling programs for conservation management.
Context. The Illinois Department of Natural Resources was mandated by legislation to develop management plans for American Black Bears and needed Illinois residents’ preferences for bear management strategies.
Aims. The aim of this article was to examine how demographics, emotions and attitudes were related to support for three American black bear management strategies (active reintroduction, natural recolonisation, having breeding populations of black bears). Researchers have repeatedly suggested that these predictors are related to support for management actions.
Methods. Data were obtained from a mail survey sent to two populations of stakeholder groups. A total of 896 agricultural producers completed the questionnaire (response rate = 36%); 904 hunters completed the questionnaire (response rate = 36%). Five demographic variables were used in the analyses: (1) agricultural producer; (2) hunter; (3) age; (4) sex; and (5) residence growing up. Positive and negative emotional dispositions were operationalised with eight items. General attitude toward bears was measured with four items. All three management questions were asked for ‘in Illinois’ and ‘in my county’. Reliability analyses supported combining the psychological variables into indices for each construct.
Key results. Findings indicated that demographic and psychological characteristics are related to support for bear management strategies, but that these relationships are complex for a number of reasons. First, the regression beta coefficients for the demographic regression models were ‘minimal’ (M = 0.13), whereas the coefficients for psychological variables were ‘typical’ (M = 0.30). Second, not all of the demographic and psychological variables affected support for agency actions in the same way. Third, the average R2 for the three demographic models was only 16%, whereas the average R2 for the three psychological characteristics models was 53%.
ConclusionsGiven the weak relationships between demographics and support for bear management, managers may not need to always target specific groups based on their demographics.
Implications. Certain situations may warrant specific messages to target audiences; weak demographic relationships suggest that managers should be cautious when using these characteristics to target communication messages to specific groups.
Context. Striped skunks (Mephitis mephitis) occur across a wide range of habitats in North America and co-occur with many wildlife that use similar denning structures. Few studies have quantified interspecific activity at striped skunk dens despite the concomitant implications for pathogen transmission due to direct and indirect contact at shared dens. Further, no studies have examined differences in striped skunk denning behaviour across an urban–rural gradient with various forms and degrees of human modification.
Aims. Our study described striped skunk denning behaviour in the lower Midwestern United States and assessed interspecific activity at dens.
Methods. We used radiotelemetry and camera traps to observe winter denning behaviour of radiocollared striped skunks and other sympatric species across an urban–rural gradient in southern Illinois, USA, during November–February 2018–2021. We examined correlations between striped skunks and other species captured in photos at dens. We tested for an effect of human modification on the number of dens used by striped skunks, and the effects of weather and landscape variables on striped skunk denning duration.
Key results. Striped skunks used 3–21 unique dens during a single winter and denned consecutively in one location for 2–59 days. All individuals were observed denning for ≥8 consecutive days. Three striped skunks participated in communal denning, and ≤3 striped skunks were observed at a den concurrently. Eleven mammalian species were observed at striped skunk dens, and other species were present in 35.3% of photos. Striped skunk presence at a den was positively associated with Virginia opossum (Didelphis virginiana) presence. Human modification had no significant effect on the number of dens used by a striped skunk. Human modification, distance to stream/shoreline, and mean daily temperature had significant negative effects on striped skunk denning duration.
Conclusions. We demonstrated that winter denning behaviour of striped skunks in southern Illinois, USA, fits into a latitudinal gradient of behaviour across North America, and dens are a shared resource where direct and indirect intraspecific and interspecific interactions occur.
Implications. Weather and landscape features influenced winter denning behaviour of striped skunks and ultimately pathogen transmission potential at dens, trends that could potentially be seen in other urban-adapted species.
Context. Thousands of captive white-tailed deer (Odocoileus virginianus) breeding facilities exist across North America for the purpose of producing trophy-class deer (i.e. exceptionally large-antlered). Many of these deer get marketed to private landowners, with the expectation that introduced deer will enhance genetics in the population, resulting in larger-antlered male deer. Previous research suggests that survival and reproductive success of translocated wild white-tailed deer are highly variable; however, little is known about the fate of white-tailed deer translocated from captive-breeding operations.
Aims. To assess the efficacy of translocating captive female white-tailed deer for the purpose of increasing average antler size within a high-fence property.
Methods We translocated 24 adult female deer into a private, 300-ha high-fence shooting preserve in east-central Alabama over a 3-year period. We monitored survival, reproductive success, and fawn recruitment for the translocated deer by using VHF radio collars and vaginal-implant transmitters (VITs).
Key results. We found a 12-month survival rate of 0.54 for translocated deer. We captured nine fawns throughout our study, leading to a rate of 0.9 fawns per VIT, after accounting for doe mortality and premature VIT expulsion. We found 60-day and 6-month fawn survival rates of 0.33 and 0.22 respectively.
Conclusions. Survival of translocated captive deer was comparable to rates reported in previous studies that translocated wild deer, although lower than what is found in wild populations that undergo no translocation. Translocated does produced a low number of fawns relative to the national average, although fawn recruitment was within the range of survival rates reported in studies of wild deer.
Implications. We believe our findings provide a baseline of expectations for captive-deer translocations. Given our results, we believe it is infeasible to expect increased average antler size within this study site by translocating adult female white-tailed deer.
Context. Optimal foraging strategies can be influenced at the group level by population density, which can increase competition, hunger, and activity levels. Optimal foraging can also be influenced at the individual level by personality, which in part governs how individuals assess risk versus reward.
Aims. The purpose of this study was to quantify the influence of population density on risk-taking. I focused on captive elk that had previously been studied in tandem with wild elk in order to quantify personality trait characteristics. I hypothesised that risk-taking would be shown to be a density-dependent affect, in addition to varying individually.
Methods. Automated cameras recorded visitation to four rotating treatments sites in each of high and low density pens, and which had either: forage, a novel object, forage + novel object, or a control site. Novel objects were regularly changed to elicit a spectrum of responses ranging from neofilia to neophobia. Selection or avoidance of sites was determined by comparing elk visitation to visits to control sites. The experiment was done in summer when natural forage was most abundance, and in again in autumn when natural forage was limited.
Key results. High density elk showed year-round selection for all treatment sites. In summer low density elk showed weak selection for forage and forage + novel and no selection for novel objects, and no selection for any site in autumn. These patterns showed that elk in the high density pen, which were in poorer condition, had to increase their levels of both activity and risk taking. Neither elk pen exhibited any group-wide avoidance of novel objects, indicating a group-wide gradient of neophobia to neofilia, known personality traits in elk.
Conclusions. These results show that risk-taking behaviour can be a density dependent effect. This increase in neofilia may be driven by hunger stress, but also through increases in competition that may favour elk of certain personalities.
Implications. Increasing density may increase the prevalence of both neofilia and other personality traits correlated with neofilia, which include aggression, and so may contribute to increasing human–wildlife conflicts in areas where human disturbance has resulted in ungulate hyperabundance.
Context. Wildlife is ubiquitous in urban environments, resulting in frequent interactions with humans and human infrastructure. The result of these interactions is often negative, in the form of road injury, orphaning of dependent young or eviction from natural home ranges. Wildlife rehabilitation programmes are devised to counter these negative interactions. However, the success of current management strategies is rarely assessed.
Aims. We aimed to determine whether short-term survival of juvenile hand-reared common brushtail possums (Trichosurus vulpecula) released in the wild was a function of (1) intrinsic factors such as sex, individual personality and level of human habituation, and (2) extrinsic factors such as release practice (soft vs hard-release) or location (urban vs rural). We also evaluated the relationship between habituation to humans and time spent in care by possums, if presence of conspecifics during the rehabilitation process influenced the development of individual personality, and if this differed in hand-raised animals compared with wild individuals.
Methods. We radio-tracked and monitored 20 hand-reared juvenile possums (10 females and 10 males) for up to 40 days after release in the wild.
Key results. Eight possums (40%) survived until the end of the study, nine possums (45%) were killed by foxes or had to be returned into care and three possums (15%) had unknown fates (i.e. lost VHF signal). We found that more exploratory individuals and those less human-habituated were more likely to be successful in the wild in both rural and urban areas, whether or not they were hard or soft released.
Conclusions. Our results suggest that personality is a key criterion to consider when evaluating the success of rehabilitation programmes. Behavioural traits of hand-reared brushtail possums differed significantly from those of wild individuals, showing that captive conditions can affect the development of personality. Hand-reared possums that spent more time in care were also more likely to display highly human-habituated behaviours.
Implications. By demonstrating which factors influence success of hand-reared wildlife after release in the wild, our results help in evaluating current rearing and release practices, and improve the evidence base for developing best practice wildlife rehabilitation guidelines.
Context. The fluctuating fortunes of the brush-tailed bettong have seen this species classified as ‘Rare or Likely to Become Extinct’ in the 1970s, delisted and hailed as a conservation success in the 1990s, and re-listed as ‘Critically Endangered’ in 2008. Key actions to recover this species, broad-scale fox control and reintroduction to fox-free habitat, have had variable success.
Aims. To monitor the reintroduction of bettong to fox-free habitat of Wadderin Sanctuary in the eastern wheatbelt of Western Australia.
Methods. Growth of the population was monitored over a 12-year period by regular trapping throughout the sanctuary.
Key results. The population increased monotonically to peak at 305 individuals (0.71 ha−1) at 7.5 years following release, before subsequent decline. Population growth was accompanied by a significant decline in mean condition and a reduction in the proportion of females with pouch young or lactating, presumably owing to resources per head gradually declining. The proportion of large pouch young relative to total young carried by females declined as woylie numbers increased, suggesting that, increasingly, pouch young did not go to full term. Declines in population number, condition and reproduction were exacerbated by dry seasons. Bettongs established successfully, despite a succession of single feral cats within the 427-ha sanctuary. The removal of the last cat, 8 years following the establishment of bettongs, had no obvious impact on bettong numbers, as, at this point, their population was stabilising because of declining body condition and reduced reproductive output.
Conclusions. The observed pattern of population growth of bettongs was consistent with an herbivore irruption consequent of a release of a species to new habitat. Decline following peak numbers appeared as a result of density-dependent resource limitation (declining resources per head with increased abundance) interacting with years of low rainfall.
Implications. The dynamics of irruption and decline of herbivores are relevant to management of reintroduced populations to fenced predator-free sites and, potentially, to unfenced populations following release from predation.
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