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Data from animals equipped with global positioning system collars have advanced our understanding of vertebrates, but this technology has rarely been employed to study feral equids. Hesitation to equip feral equids with telemetry collars in the USA can often be attributed to safety concerns stemming from one study from the 1980s, where injuries were sustained by feral horses (Equus ferus caballus) equipped with radio-collars. Improvements in collar design over the ensuing quarter-century may have decreased risk of collar-related complications; however, telemetry-based studies on feral equids continue to be limited. In the present review, studies from wild and feral equids worldwide were systematically reviewed to better understand the mortality and injury risk in application of telemetry collars to equids. Our goals were to: (1) report the number of individual equids fitted with telemetry collars (1979–2017); and (2) document the number of individual equids that reportedly died or suffered injuries from collars or other sources. A comparative review of elk (Cervus canadensis), mule deer (Odocoileus hemionus) and pronghorn (Antilocapra americana) was also conducted to evaluate the relative risk of collar-related complications among equids and routinely collared North American ungulates. In total, 1089 wild and feral telemetered equids were identified across 48 studies. Of these, 87 (8.0%) were reported to have died, with only one (0.09%) mortality attributable to a collar. Comparatively, 23.0% (1095) of 4761 elk, mule deer and pronghorn fitted with telemetry collars were found to have died in the same number of studies, though no mortalities were reported to be related to the collar. Although wild and feral equids did not experience increased natural mortality compared with the other ungulates, studies have not provided sufficient information to assess relative risk of collar-related complications. Explicit reporting and discussion of telemetry collar impacts in future publications of all animal species are recommended, especially equids, to improve understanding of how telemetry collars can affect study individuals.
Context. Estimates of a species abundance and habitat preferences provide vital information on their status and the appropriate conservation management. For nocturnal arboreal primates, obtaining reliable estimates of these parameters is particularly challenging because of their cryptic behaviour, often resulting in a small number of detections. Although techniques are available for assessing the abundance of species with a low probability of detection, most require strict assumptions that are difficult to meet.
Aims. Here, we aimed to explore the possibility of improving nocturnal-primate abundance estimates when detection probability is low and to determine the minimal effort required to calculate reasonable estimates of their overall abundance and the effect of habitat type on abundance estimates.
Methods. We used count data obtained from spotlighting along line transects for estimating density of Bengal slow loris (Nycticebus bengalensis) in north-eastern Thailand with N-mixture hierarchical modelling, to run simulations of varying survey parameters and asses the effort needed to produce robust estimates based on the relative bias from each simulation.
Key results. N-mixture analysis showed that the data obtained from our study were still biased (9%), with a lambda of 1.79 lorises, detection probability of 0.11, 50 survey sites and a maximum of 12 sample occasions. The simulation results found that increasing the number of sample occasions to 14 per transect would produce an acceptable bias (<5%).
Conclusions. We recommend that future studies on nocturnal arboreal species should use preliminary surveys to gauge the specific lambda and probability of detection so as to establish the effort needed to produce reasonable estimates of abundance.
Implications. Our study showed that count data obtained from spotlighting can be used to produce robust abundance estimates of nocturnal arboreal species. Unlike simple encounter rate, this method incorporates detection probability and habitat preferences, yet does not require additional trained field technicians.
Context. In Australia, various species of macropods (family Macropodidae) are known to occur within peri-urban areas, where they can be a source of human–wildlife conflict. Some species, such as the eastern grey kangaroo (Macropus giganteus), have received considerable research attention over the past few years following demands from land managers for evidence-based management guidelines; however, the ecology of other macropod species found in peri-urban areas, such as the eastern wallaroo (Osphranter robustus robustus), remains poorly understood.
Aims. The aims were to determine the home range of male and female eastern wallaroos and assess habitat selection in order to define whether wallaroos in a peri-urban environment should be viewed as thriving (‘matrix-occupying’), persisting (‘matrix-sensitive’) or struggling (‘urban-sensitive’).
Methods. Home range and habitat use of six adult male, five adult female and one subadult male eastern wallaroo were investigated using GPS telemetry between October 2017 and May 2018 in the south-west of Sydney.
Key results. Home ranges (mean ± s.e.) of males (63.1 ± 10.2 ha) were significantly larger than those of females (31.1 ± 3.3 ha). Every adult wallaroo had highly overlapping monthly home ranges, indicating strong site fidelity in all individuals. Eastern wallaroos selected habitats based on vegetation composition during the night and canopy cover during the day. Grassland and open native woodlands were preferred during foraging activities at night. By contrast, human-modified habitats, including hard surfaces and lawns, were avoided at all times by all individuals.
Conclusion. The results indicate that eastern wallaroos avoid human-modified features in the landscape, so they could be viewed as persisting (‘matrix-sensitive’) in peri-urban areas.
Implications. Compared with matrix-occupying macropods, such as the eastern grey kangaroo, the eastern wallaroo is less likely to cause human–wildlife conflicts – a result of its avoidance of human-modified habitat. Land-use planning, involving green corridors linking remnant vegetation, should be implemented as part of urban planning to enable the persistence of diverse mammal populations in urban areas, particularly matrix-sensitive species.
Context. The ring-necked pheasant (Phasianus colchicus) has experienced considerable population declines in recent decades, especially in agricultural environments of the Central Valley of California. Although large-scale changes in land cover have been reported as an important driver of population dynamics, the effects of microhabitat conditions on specific demographic rates (e.g. nesting) are largely unknown.
Aims. Our goal was to identify the key microhabitat factors that contribute to wild pheasant fitness by linking individual-level selection of each microhabitat characteristic to the survival of their nests within the California Central Valley.
Methods. We radio- or GPS-marked 190 female ring-necked pheasants within five study areas and measured nest-site characteristics and nest fates during 2013–2017. Specifically, we modeled microhabitat selection using vegetation covariates measured at nest sites and random sites and then modeled nest survival as a function of selecting each microhabitat characteristic.
Key results. Female pheasants tended to select nest sites with greater proportions of herbaceous cover and avoided areas with greater proportions of bare-ground. Specifically, perennial grass cover was the most explanatory factor with regard to nest survival, but selection for increasing visual obstruction alone was not shown to have a significant effect on survival. Further, we found strong evidence that pheasants selecting sites with greater perennial grass height were more likely to have successful nests.
Conclusions. Although pheasants will select many types of vegetation available as cover, our models provided evidence that perennial grasses are more beneficial than other cover types to pheasants selecting nesting sites.
Implications. Focusing management actions on promoting perennial grass cover and increased heights at the microsite level, in lieu of other vegetative modifications, may provide improved quality of habitat for nesting pheasants and, perhaps, result in increased productivity. This is especially important if cover is limited during specific times of the nesting period. Understanding how microhabitat selection influences fitness can help land managers develop strategies to increase the sustainability of hunted populations of this popular game-bird species.
Context. For migratory animals, particularly those with long generation times, changing weather patterns may cause a mismatch between periods of expected and actual resource availability, termed phenological mismatch. The cave-dwelling Natal long-fingered bat (Miniopterus natalensis) is a regional migrant within South Africa for which the (hitherto unknown) phenology of migration may be affected by climate.
Aims. To investigate the migration phenology of the Natal long-fingered bat in relation to climate at a maternity cave in South Africa.
Methods. Five years (2014–18) of echolocation data from a maternity cave site in Limpopo, South Africa, were studied. Separate stepwise General Linear Models (GLMs) were constructed for each season using photoperiod, minimum temperature, dew point, rainfall, barometric pressure, humidity and maximum wind speed. Arrival and departure dates among years were also compared.
Key results. Photoperiod had the greatest effect on the magnitude of Natal long-fingered bat phenological patterns in activity across all seasons. Although spring (September - November) arrival at the maternity site was variable across years, summer departure dates did not differ, resulting in a shorter breeding period in the 2017–18 sample year. During the 2016–17 sample year, the magnitude of Natal long-fingered bat activity was significantly lower than in other years, which coincided with El Niño-induced drought conditions and likely impacted resources and led to a reduction in activity and population size.
Conclusions. Photoperiod is a strong predictive cue of the phenology of migration of the Natal long-fingered bat and likely cues migration for this species. The narrow departure dates of these bats from the maternity site supports these results.
Implications. The present study indicates that Natal long-fingered bats use photoperiod as a migration cue and do not appear to shift their spring–summer breeding season, likely making them vulnerable to phenological mismatch and population decline. The research highlights the need for systematic population monitoring for the Natal long-fingered bat.
Context. Translocations have been widely used to re-establish populations of threatened Australian mammalian species. However, they are limited by the availability of sites where key threats can be effectively minimised or eliminated. Outside of ‘safe havens’, threats such as exotic predators, introduced herbivores and habitat degradation are often unable to be completely eliminated. Understanding how different threats affect Australian mammal populations can assist in prioritising threat-management actions outside of safe havens.
Aims. We sought to determine whether translocations of the greater bilby to two sites in the temperate zone of South Australia could be successful when human-induced threats, such as prior habitat clearance, historic grazing, the presence of feral cats and European rabbits, could not be completely eliminated.
Methods. Greater bilbies were regularly cage trapped at two translocation sites and a capture–mark–recapture study was used to determine survival, recruitment and population growth at both sites.
Key results. Our study showed that bilbies were successfully translocated to an offshore island with a previous history of grazing and habitat clearance, but which was free of exotic predators. At a second site, a mainland exclosure with feral cats and European rabbits present, the bilby population declined over time. Adult bilbies had similar survival rates in both populations; however, the mainland bilby population had low recruitment rates and low numbers of subadults despite high adult female fecundity.
Conclusions. The results indicated that past grazing and habitat clearance did not prevent the bilby population on the offshore island establishing and reaching a high population density. In the mainland exclosure, the low recruitment is probably due to feral cats predating on subadult bilbies following pouch emergence.
Implications. The results demonstrated that the bilby, an ecologically flexible Australian marsupial, can be successfully translocated to sites with a history of habitat degradation if exotic predators are absent. At the mainland exclosure site, threat mitigation for bilbies should focus on control or eradication of the feral cats. The control of European rabbits without control of feral cats could lead to prey-switching by feral cats, further increasing predation pressure on the small bilby population.
Context. Translocation is a widely used non-lethal tool to mitigate human–wildlife conflicts, particularly for carnivores. Multiple intrinsic and extrinsic factors may influence translocation success, yet the influence of release-site landscape context on the success of translocations of wildlife involved in nuisance behaviour is poorly understood. Moreover, few studies of translocated wildlife involved in nuisance behaviour have provided estimates of translocation success under different scenarios.
Aims. We evaluated the role of intrinsic (age, sex) and extrinsic (translocation distance, landscape composition) features on translocation success of American black bears (Ursus americanus) involved in nuisance behaviour and provide spatially explicit predictions of success under different scenarios.
Methods. We analysed data from 1462 translocations of 1293 bears in Wisconsin, USA, from 1979 to 2016 and evaluated two measures of translocation success: repeated nuisance behaviour and probability of returning to a previous capture location.
Key results. Translocation distances ranged from 2 to 235 km (mean = 57 km). Repeated nuisance behaviour was recorded following 13.2% of translocation events (192 of 1457) and was not significantly affected by translocation distance. Bears repeated nuisance behaviour and were recaptured at their previous captures site (i.e. returned) after 64% of translocation events (114 of 178). Return probability decreased with an increasing translocation distance, and yearling bears were less likely to return than were adults. The proportions of agriculture and forest within 75 km and 100 km respectively, of the release site had positive and negative effects on return probability.
Conclusions. Mangers can use bear characteristics and landscape context to improve translocation success. For example, achieving a 10% predicted probability of return would require translocation distances of 49–60 km for yearlings in low-agriculture and high-forest landscapes. In contrast, estimated return probability for adults was ≥38% across all translocation distances (0–124 km) and almost all landscape contexts.
Implications. Our results emphasise the importance of considering the effects of landscape conditions for developing spatially explicit guidelines for maximising translocation success.
Context. Eradication of invasive rodents on islands typically results in positive conservation gains, and maintaining a rodent-free island requires elevated biosecurity, including prevention of assisted rodent arrival via watercraft, aircraft and animals such as birds. Cattle egrets (Bubulcus ibis) are widespread, and often fly several kilometres daily to roost and forage. They frequently swallow insects and vertebrates (including rodents) whole, and some regurgitate prey. Cattle egrets have been regularly observed flying between the Hawaiian Islands of Ni’ihau (where non-native mice and rats are established) and Lehua (where one species of non-native rat is established and was targeted during a recent eradication attempt).
Aims. The objectives were to identify the species of rodent that cattle egrets regurgitate following transport between Ni’ihau and Lehua islands, and to determine if any of the rodent individuals regurgitated were alive once deposited onto Lehua Island following 1.1-km oversea flights.
Methods. Eighty-five individual rodent carcasses (regurgitated by cattle egrets) were collected, preserved and identified to species using morphological characteristics and DNA sequencing.
Key results. All rodents regurgitated by cattle egrets were dead upon collection on Lehua Island. Although the Pacific rat (Rattus exulans) is the only rodent species on Lehua Island, and field staff suspected the regurgitated rodents were R. exulans, all 85 carcasses were identified as house mice (Mus musculus).
Conclusions. This is the first evidence (that the authors know of) showing movement of rodent carcasses, via cattle egrets, between islands.
Implications. Cattle egrets that deposit rodent carcasses onto rodent-free islands, or segments of islands, may confuse land managers and biosecurity professionals who are unaware of this phenomenon. House mice did not survive cattle egret ingestion, >1-km flight and regurgitation; therefore it is unlikely that live rodents would be introduced to rodent-free areas via cattle egrets.
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