共查询到20条相似文献，搜索用时 31 毫秒
1.
The successful introduction of captive bred takhi or Przewalski’s horse, Equus ferus przewalskii, into Mongolia in the 1990s is a good example of the benefits of ex situ conservation and one of the few examples of the recovery of an animal after it became extinct in the wild. This is also particularly interesting because virtually nothing was known about how takhi lived before they died out, and the introductions have enabled us to study how they have settled, and their ecology and behaviour within their former natural range. In this paper, we describe the movement, home range size and shape, and habitat use of takhi at one of the release areas, the 570 km2 Hustai National Park in Mongolia. Harem home ranges varied between 129 and 2399 ha, with 80% core areas of between 61 and 1196 ha. There was no relationship between range size and harem size, or length of time since release. Initially, harems stayed near their release enclosures, but over time they established home ranges further away. There was little overlap between home ranges of different harems, but neither was there evidence of exclusive range use. The more nutritious vegetation at lower elevations was preferentially selected. Thus the present situation looks good, but, as the population continues to grow, we anticipate that there will be potential problems related to intraspecific competition for water and vegetation resources, and the potential for hybridisation with domestic horses belonging to the local people. We consider the time it may take for takhi to reach carrying capacity within Hustai National Park and emphasise that continual monitoring of the population is essential because interventional management is likely to be required in the future. 相似文献
2.
The dehesa (oak woodland) is an extensive agro-pastoral ecosystem characteristic of the Western Mediterranean countries which is suffering a great transformation process since 1950. Although its distribution largely overlaps with several endangered species, there is scarce information on how they use this human-transformed habitat. We studied the foraging habitat selection of one of them, the cinereous vulture Aegypius monachus. We radio-tracked 14 cinereous vultures in one of the largest European colonies from 1998 to 2000. Used and available habitats were compared at two scales using compositional analysis. Moreover, we developed a distance-based GLMM for assessing habitat selection in this central-place forager species, by taking into account the spatial distribution of habitat patches in relation to the location of the colony. Home ranges overlapped over a total surface of 592,527 ha around the colony, and both individual home ranges and travel foraging distances (mean 27.86 km, maximum 86 km) were larger during the breeding season. All cinereous vultures avoided agricultural lands within their home ranges throughout the year. Habitat use in relation to the distance to the colony pointed out that dehesas were positively selected in spite of being on average far away from the colony than other habitats, a result that was consistent among individuals and seasons. The cinereous vulture thus depends for its conservation not only on the protection of breeding areas, as has been so far considered, but also on the maintenance of well-conserved dehesas close to the colonies. Preserving the cinereous vultures could contribute to the economic sustainability of dehesas by attracting PAC funds for their traditional low-intensity exploitation. Although other species may also benefit from this study since cinereous vulture could be a “flagship” for the large-scale conservation of Mediterranean oak woodlands and associated biodiversity, more fine local management guidelines should be performed on the basis of studies on more sensitive species. 相似文献
3.
Evaluating translocation outcomes is important for improving wildlife management and conservation actions. Often, when quick decisions need to be made and long-lived animals with slow reproduction rates are translocated, traditional assessment methods such as long-term survival and reproductive success cannot be used for assessing translocation outcomes. Thus, alternative, seldom used, measures such as comparing the behavior and physiology of translocated animals to those of local residents should be employed to assess the translocated animals’ acclimation to their new home. Here we monitored the survival, physiology, and behavior of translocated African elephants (Loxodonta africana) and compared these measures to the local resident population at the release site. Adult male and female translocated elephants’ death rates were higher than those of the local population. Furthermore, the mortality rate of translocated adult males and calves was greater than expected based on their proportion in the translocated elephant population. No difference was found in stress hormone levels between the two populations, but the body condition of the translocated elephants was significantly poorer than that of the local population throughout the study period. The behavioral time budgets of the translocated elephants converged with those of the local population over time. Finally, translocated elephants utilized habitat that was similar to their source site (hills and permanent rivers) more than did the local population. Based on these findings we recommend careful consideration of timing, release location, and individuals targeted in future elephant translocations. More broadly, we introduce and explore seldom used translocation assessment techniques. 相似文献
4.
We assessed home range size for breeding loggerhead turtles (Caretta caretta) near the limit of the species range at the Greek island of Zakynthos in the Mediterranean. Thirteen adult females and seven adult males were tracked using GPS units (loggers and transmitters) during May and June of 2006, 2007 and 2008. Kernel analysis indicated that core home range sizes (50% estimator; range: 2.9-19.7 km2) for both males and females were restricted to a 7.5 km tract of coastline. 15% of GPS locations fell outside of the national park protection zones, while within the protected breeding area 88% of GPS locations occurred in zones of minimal protection. Female home ranges were 64% larger in 2008 than in 2006 and 2007, indicating that several years monitoring may be required for the most effective designation of marine protected areas (MPAs). Ten of the tracked females departed the core breeding area on 15 occasions for periods of 1-15 days travelling distances of 10-100 km, although none nested at alternative breeding sites. The inter-annual variability of breeding area home range size and likelihood of incidence of forays appeared be correlated with barometric pressure. The movement responses of loggerheads to environmental conditions implicates an ability to switch nesting areas over small scales in response to climate change. However, such behaviour suggests the protection of existing core breeding sites may be inadequate, with policy makers being required to consider the protection of broader areas to encompass potential changes in the habitat needs of this species. 相似文献
5.
Satellite tracking of black storks was used to estimate home range sizes and to study habitat selection during the breeding season. Breeding and non-breeding adults foraged over very large areas (ca. 54 000 ha for 12 territories), preferentially in woodlands with high number of river sources, mirroring the species needs for high quality water resource. Rearing and post-fledging ranges of breeding partners largely overlapped. Home ranges of non-breeding adults largely overlapped ranges of breeding birds, so that assessing home range size of breeding pairs from observed densities is not reliable. Protection and management of breeding and feeding habitats appear to be the most important conservation measures to be considered. This study allowed to evaluate how large these protected areas should be, and which habitat types they should encompass. Conservation measures for the species in western Europe should include protection of very large forest areas and also focus on managing river networks to ensure a high water quality as far as 20 km away from nests. 相似文献
6.
Understanding the movement and habitat use patterns of threatened species is essential to effective conservation planning. Modern tracking techniques such as active tracking and passive acoustic monitoring can be useful tools in elucidating this information for aquatic species. To aid in the development of conservation strategies for juvenile critically endangered smalltooth sawfish (Pristis pectinata) their fine scale movements and habitat use in southwest Florida were studied using a combination of these techniques. Between 2002 and 2006 a total of 12 individuals were actively tracked for periods of up to 24 h to provide detailed habitat use and movement parameters (distance moved, speed, and linearity). Smaller individuals (<100 cm stretched total length (STL)) had the smallest home ranges, low linearity of movement and had a preference for very shallow mud banks. Juveniles >100 cm STL demonstrated larger home ranges, preference for shallow mud or and sand banks, and remained close to mangrove shorelines. Tide was found to be the main factor influencing movement on short time scales. Sawfish <150 cm STL spend the majority of their time in water <50 cm, while larger juveniles spend most of their time in water 50-100 cm deep. From 2003 to 2007 a total of 22 individuals were fitted with acoustic tags for long-term monitoring. Juveniles >130 cm had high levels of site fidelity for specific nursery areas for periods up to almost 3 months, but the smaller juveniles had relatively short site fidelity to specific locations. The use of a combination of tracking and monitoring techniques provided an expanded range of information by generating both short and long term data on habitat use. The data demonstrated that the conservation of shallow mud and sand banks, and mangrove shorelines will benefit the recovery of these endangered elasmobranchs. 相似文献
7.
Translocation of species for conservation purposes is a key element of many recovery programs. While the benefits of translocations seem obvious, potential negative effects have been described. For endangered beach mice (Peromyscus polionotus ssp.), repopulation of native, unoccupied habitat using translocated individuals has been extremely successful. Once populations are established, concerns over founder effects and isolation have led to proposals for continued secondary translocations. Unfortunately, little information is available to help formulate protocols for these actions. To test the effectiveness of translocation, the fates of 18 translocated Choctawhatchee beach mice (Peromyscus polionotus allophrys) were followed as they attempted to integrate into an established population. We found that translocated groups, repeated for two seasons, tended to use larger homeranges and significantly more burrows than did resident mice. The monthly (31 day) survival rate of resident mice was 3.4 times greater than for translocated individuals. We hypothesize that differential predation pressure was directly linked to the failure of mice to integrate successfully into the existing population. Given our results, we must advise caution and that additional knowledge be obtained before translocations are used to supplement existing populations. 相似文献
8.
Quantifying the movement of exploited species inside marine reserves is a popular research topic, yet few studies have quantified movement inside and outside of reserves. If individuals inside reserves behave differently to those outside, this information should be incorporated into reserve design and in management efforts to avoid the selective removal of certain behaviors. We used acoustic telemetry to monitor the movements of the sparid Pagrus auratus (snapper) inside and outside a marine reserve (the Leigh Marine Reserve, north-eastern New Zealand). We tagged 39 snapper within an array of acoustic receivers that encompassed reserve and fished areas. Nineteen snapper were resident over a 5-month period; the remainder either left the array or died. Residential fish expressed two home range types. One group had uni-modal home ranges that on average encompassed c.900 m linear distance. All nine residential snapper from the reserve displayed this behavior, as well as five of ten residential fish from the non-reserve area. The second group (five fish, all from the non-reserve area) had home ranges with two separate modes (bi-modal home ranges), which on average encompassed c.2 100 m linear distance. We suggest that some aspect of the marine reserve environment encourages extreme residency by either the modification of individual behaviors or through the removal of selective exploitation. If true this suggests that reserves and populations of exploited animals may become dependent on the life history characteristics of the individuals they encourage or select for. 相似文献
9.
The Gila Monster (Heloderma suspectum) is a large, venomous lizard protected throughout its distribution in the southwestern United States and northwestern Mexico. Rapid urban growth in key areas of its range and increased encounters with humans prompted us to investigate translocation as a conservation tool with “nuisance” Gila Monsters. Twenty-five Gila Monsters reported as nuisances by residents in the northeastern Phoenix Metropolitan Area were translocated from 0 to 25,000 m from their point of capture. Subjects (N=18) translocated less than 1000 m returned to their original site of capture within 2-30 days; none of those (N=7) translocated more than 1000 m successfully returned, they exhibited high daily rates of speed, and were deprived the use of familiar refuges. We conclude that small distance translocations within suitable habitats are ineffective in removing Gila Monsters from areas deemed unsuitable. Moreover, individuals moved significantly greater distances are unlikely to remain at a translocation site, and may experience a variety of costs (e.g., predation risk) associated with high rates of movement. 相似文献
10.
The Ljubljana-Razdrto highway and the parallel Ljubljana-Trieste railway cut through critical brown bear (Ursus arctos) habitat in south-central Slovenia. These high speed, high volume traffic axes are located close to the main dispersal corridor for bears from the Dinaric Mountain range into the Alps. We analyzed radiotracking data of 15 individual bears that lived within 10 km of the highway, compared transportation related and overall known bear mortality, and analyzed the spatial distribution of bear-vehicle accidents. The highway posed a home range boundary to resident bears, but was not an absolute barrier. Transportation-related mortality was high in the vicinity of the highway and railway, and averaged 31% of the total known local mortality from 1992 to 1999. At present the detrimental impact of transportation routes on the bear population in Slovenia is modest due to the high density of bears and the low density of highways—but new highways are planned or already under construction. Managers have to be aware that, due to bears large home ranges and long dispersal distances, a single highway affects bears from a huge area—emphasizing the importance of international cooperation and a landscape approach in highway planning. 相似文献
11.
Gould’s petrel (Pterodroma leucoptera leucoptera) was restricted, essentially, to a single breeding locality - Cabbage Tree Island, Australia. As a safeguard against extinction, an additional breeding colony was established on nearby Boondelbah Island, where artificial nesting habitat was created by installing 100 plastic nest boxes. Over two years, a total of 200 nestling Gould’s petrels were translocated from Cabbage Tree Island to these boxes. Colonies on both islands were then monitored for a further four years. Selection of nestlings for transfer was based on prior knowledge of growth, plumage development and emergence from the burrow, and aimed to select only birds that were 11-28 days from fledging (DBF) in 1999 and 11-22 DBF in 2000. Of the first 100 nestlings translocated to Boondelbah Island (in March 1999), 95 fledged successfully 8-27 days after transfer (mean = 17.3 days). Of the second 100 nestlings translocated (in March 2000) all successfully fledged 9-22 days after transfer (mean = 15.1 days). The removal of young had no discernible effect on the subsequent breeding productivity of the donor pairs. In all, 41 Gould’s petrels have been recorded at the new colony on Boondelbah Island, where at least 27 nest boxes have been visited. Ten translocated fledglings (nine male, one female) have returned to the translocation site, taking up nest boxes that were, on average, 5.5 m from the box from which they fledged. An additional 27 non-translocated birds, of unknown origin, have also nested in nest boxes on Boondelbah, along with four birds previously known from Cabbage Tree Island. Two nestlings transferred to Boondelbah Island have returned to Cabbage Tree Island. Within five years of the first translocation, the newly established colony on Boondelbah Island has produced a total of 24 eggs and 14 fledglings. The translocation technique developed for Gould’s petrel has broad applicability, being readily adaptable for other burrow-nesting seabirds. 相似文献
12.
Endangered birds in insular environments like New Zealand are often translocated to predator-free offshore islands for conservation purposes. Some translocated populations however exhibit reduced fecundity, and it has been suggested that either inbreeding (due to small number of founders) or resource shortages (due to high population density) may limit reproductive success. For example, the South Island robin (Petroica a. australis) population on Motuara Island (59 ha) was founded by only five birds but has increased to ∼600 individuals, or a density >10 times that of the mainland. Despite this apparent success, the rate of hatching failure in this population is three times higher than in mainland populations, with more than a third of eggs failing to hatch. To test if elevated hatching failure is the result of food limitation, we carried out a food supplementation experiment by providing females with mealworms equivalent to ∼50% of their daily energy requirements. Food supplementation had no effect on hatching success, clutch size, incubation attentiveness or nest size. Egg volume increased with food supplementation in one of the two years of this study, but both egg volume and incubation attentiveness were unrelated to rate of hatching failure. As previous genetic analyses confirmed that the bottlenecked population of robins on Motuara Island have significantly less genetic variation than their source population, we conclude that inbreeding depression, and not food limitation, is the most likely explanation for their high rate of hatching failure. We suggest that the experimental translocation of genetically dissimilar individuals be considered as a possible remedy for low productivity in island populations that were initiated with few founders. 相似文献
13.
David S. Maehr E.Darrell LandDavid B. Shindle Oron L. BassThomas S. Hoctor 《Biological conservation》2002,106(2):187-197
We studied dispersal in 27 radio-collared Florida panthers Puma concolor coryi in southern Florida from 1986 to 2000. Male dispersal was longer (mean=68.4 km) than that of females (mean=20.3 km), tended to be circular, frustrated, and of insufficient length to ameliorate inbreeding. Females were philopatric and established home ranges that were less than one home range width away from their natal ranges. All females were successful in establishing territories, whereas males were successful 63% of the time. Dispersing panthers avoided moving toward the southeast and into an area of limited forest cover. Independence and the initiation of dispersal occurred at about 14 months of age and lasted for an average of 7.0-9.6 months for females and males, respectively. On average, Florida panthers disperse shorter distances than are typical for western populations of Puma concolor. A recent increase in long distance male dispersal events may be related to an increase in reproduction and population density resulting from the introduction of female cougars P. c. stanleyana into south Florida. Although the population exhibits the behavioral ability to colonize nearby vacant range, females have yet to do so. Successful dispersal to these areas could be facilitated by habitat restoration and translocation of females. 相似文献
14.
Nina Klar Néstor Fernández Stephanie Kramer-Schadt Mathias Herrmann 《Biological conservation》2008,141(1):308-319
Populations of the European wildcat (Felis silvestris) are only slowly recovering in Central Europe after a severe decline in the last centuries and require specific conservation plans in many areas. However, detailed information on wildcat occurrence and habitat requirements is still scarce and controversial. We present a fine-scale habitat selection model for wildcats based on detailed species and land use information and evaluate its accuracy to predict habitat distribution in new areas. We analysed habitat use within home ranges using single locations of 12 radio-tracked individuals from south western Germany. Several competing models were fitted and compared using generalised linear mixed models (GLMM) and information-theoretic approaches. Radio-tracking data of 9 and 10 wildcats from two distant areas were used to evaluate the models. The selected model predicted habitat associated to close distance to forest, watercourses and meadows and a critical distance to villages, single houses and roads. To predict area suitable for home ranges we superimposed rules derived from home range attributes at a higher level of selection. Predictions from the combination of the fine-scale habitat model and home range rules matched well with more than 2000 wildcat observations of south-western Germany. We discuss the application of the model in wildcat conservation for finding potential reintroduction sites, identifying small isolated populations and aiding in the evaluation of the needs of mitigation and compensation within the scope of the European Habitats Directive. 相似文献
15.
Human development often favors species adapted to human conditions with subsequent negative effects on sensitive species. This is occurring throughout the urbanizing world as increases by generalist omnivores, like some crows and ravens (corvids) threaten other birds with increased rates of nest predation. The process of corvid responses and their actual effects on other species is only vaguely understood, so we quantified the population response of radio-tagged American crows (Corvus brachyrhynchos), common ravens (Corvus corax), and Steller’s jays (Cyanocitta stelleri) to human settlements and campgrounds and examined their influence as nest predators on simulated marbled murrelet (Brachyramphus marmoratus) nests on Washington’s Olympic Peninsula from 1995 to 2000. The behavior and demography of crows, ravens, and jays was correlated to varying degrees with proximity to human development. Crows and ravens had smaller home ranges and higher reproduction near human settlements and recreation. Annual survival of crows was positively associated with proximity to human development. Home range and reproduction of Steller’s jays was independent of proximity to human settlements and campgrounds. Local density of crows increased because home ranges of neighboring breeding pairs overlapped extensively (6× more than ravens and 3× more than Steller’s jays) and breeders far from anthropogenic foods traveled 10s of kilometers to access them. Corvids accounted for 32.5% of the predation events (n = 837) we documented on artificial murrelet nests. Small corvids (jays) were common nest predators across our study area but their contribution as predators did not vary with proximity to settlements and campgrounds. In contrast, large corvids (crows and ravens) were rare nest predators across our study area but their contribution varied greatly with proximity to settlements and campgrounds. Managers seeking to reduce the risk of nest predation need to consider the varied impacts and variable behavioral and population responses of potential nest predators. In our situation, removing large corvids may do little to reduce overall rates of nest predation because of the diverse predator assemblage, but reducing anthropogenic food in the landscape may be effective. 相似文献
16.
Ross M. Wanless Jessica CunninghamPhilip A.R. Hockey Janet Wanless Richard W. WhiteRachel Wiseman 《Biological conservation》2002,107(2):203-210
Humans and introduced mammalian predators have caused local extinctions and range reductions in the rallid genus Dryolimnas (endemic to western Indian Ocean islands); today two subspecies survive, one on Madagascar and one on three islands (ca. 8000 birds) of Aldabra Atoll. Domestic cats (Felis catus) still occur on Aldabra and their presence poses a significant potential threat to the rails. Reintroduction to cat-free islands would significantly improve their conservation status. In 1999, 20 rails were captured and brought to now cat-free Picard Island (the third largest island of Aldabra Atoll). Two rails died in captivity but all 18 remaining birds were released and survived beyond the first breeding season. Eight pairs had bonded and bred successfully within 2 months of release, producing a minimum of 13 chicks. Eleven monitored pairs produced 20 chicks in 2000/2001, with 1-year-old birds breeding successfully. Average chick production was significantly higher in the reintroduced population than in the source population in both breeding seasons. The reintroduced population at the end of the 2001 breeding season was at least 51, an increase of 283% in 18 months. Around 20 pairs are expected to attempt breeding on Picard in the third season after reintroduction, with excellent prospects for continued, exponential population growth in the medium-term. The soft-release reintroduction protocol allowed monitoring of individual birds' health before release into the wild. This is believed to have played a crucial role in the success of the reintroduction by allowing individuals to acclimatise and providing additional energetic reserves for the period between release and self-sufficiency. A soft-release is recommended as the conservative and precautionary method of choice for avian reintroductions and translocations. 相似文献
17.
The riparian brush rabbit (Sylvilagus bachmani riparius) is an endangered species found in dense, brushy habitat in the California’s Central Valley. We implemented a reintroduction program to bolster populations at a Federal Wildlife Refuge and to assess factors influencing mortality and subsequent survival of released individuals. Between July 2002 and July 2005, we reintroduced 325 captive-bred individuals to unoccupied habitat within their historic range using a soft-release strategy and monitored their subsequent survival with radiotelemetry. Longer time in soft-release pens resulted in increased monthly survival. Rabbits were most susceptible to post-release mortality during the first 4 weeks following reintroduction and both body mass and length of time in the soft-release enclosure influenced this relationship. When we controlled for release mortality during this acclimation period, subsequent monthly survival probabilities were most strongly influenced by release year (year 1 vs. years 2 and 3) and by a catastrophic flooding event; length of time in the soft-release enclosure remained an important variable in longer-term survival. Cause of mortality was unknown for the majority of deaths (61.9%), but predation (including presumptive predation) was the greatest known cause of death in translocated rabbits (26.4%). Reintroduction programs should employ an adaptive management approach with ongoing monitoring of target animals and concurrent analysis to allow managers to adjust methods as conditions dictate. 相似文献
18.
The Red-spectacled Amazon (Amazona pretrei) is an endangered, small range and migratory parrot threatened by habitat destruction and pet trade. We modelled its geographical distribution with the objective of predicting its historical, current and future (in face of climatic changes) geographical distributions. We also tested the assumption that the species tracks similar ecological conditions while seasonally migrating. Finally, we estimated the overlap between its predicted distributions and the current protected areas network. We used eight modelling techniques in an ensemble-forecasting approach to reach consensus distributional scenarios. The modelled historical breeding and wintering ranges covered a larger area than today. Its current year-round distribution is located in the same region as before but decreased by 13%, whereas the breeding range decreased by 32%, and the wintering range by 43%. The future year-round distribution is predicted to decrease by 47% and shift to east by 2060. Even more drastic decreases in range are predicted for breeding (63%) and wintering (91%) ranges. The niches of the breeding and wintering distributions are good predictors of the records of the other season. The greatest variation (SDs) in the predictions comes from modelling tools and GCMs, and little from climatic scenarios. However, variation in predictions were small within high probability regions for modelling tools by higher everywhere for GCMs and climatic scenarios. The Red-spectacled Amazon is currently underrepresented (<1% of year-round range, and <4% of each seasonal range) in the current reserve system. A broad view over all estimated and predicted ranges revealed that a small portion of the range has a very important role in current and future conservation actions for this bird - in the northeast part of state of Rio Grande do Sul and southeast state of Santa Catarina, Brazil. 相似文献
19.
Janet L Gardner 《Biological conservation》2004,118(2):195-204
The aggregation of individuals into foraging flocks is one behavioural trait that, if disrupted, can cause the Allee effect, which is a slowing in population growth at low density or small population size, and this can greatly increase the risk of extinction. Here, I describe intraspecific flocking behaviour of a colour-banded population of speckled warblers, Chthonicola sagittata, a species that has declined across a large part of its range in the fragmented temperate woodlands of Australia. I make predictions about the context in which the Allee effect might be expressed and the consequences for the viability of populations living in small habitat remnants. Speckled warblers lived in discrete, stable social groups throughout winter, the nucleus of which was the residents from one or more adjacent breeding territories. The timing and mode of flock formation and the size of flocks varied between two winters, apparently in response to the severity of conditions; thus flocking probably facilitates increased foraging efficiency and predator detection, potentially leading to increased survival in harsh conditions. Because flock territories were up to 30 ha each, and larger territories are likely, birds living in remnants smaller than 40 ha may suffer increased mortality if there are too few birds available to form flocks of an appropriate size to facilitate the benefits of grouping when conditions are most extreme. Further, in small remnants where survival is reduced, dominance behaviour and male-male competition may act to compound the Allee effect by reducing reproductive success. Regardless of these predictions, speckled warbler populations may only be viable in remnants that are large enough to support multiple flocks, to enable rapid recruitment to breeding vacancies and thus provide adequate numbers of birds for flocking. 相似文献
20.
Ignacio T Moore Michael J Greene Darren T Lerner Randolph W Krohmer Joan Whittier 《Biological conservation》2005,121(1):91-98
Introduced species are an increasingly pervasive problem. While studies on the ecology and behavior of these pests are numerous, there is relatively little known of their physiology, specifically their reproductive and stress physiology. One of the best documented introduced pest species is the brown tree snake, Boiga irregularis, which was introduced onto the Pacific island of Guam sometime around World War II. The snake is responsible for severely reducing Guam's native vertebrates. We captured free-living individuals throughout the year and measured plasma levels of stress and sex hormones in an effort to determine when they were breeding. These data were compared to reproductive cycles from a captive population originally collected from Guam. Free-living individuals had chronically elevated plasma levels of the stress hormone corticosterone and basal levels of sex steroids and a remarkably low proportion were reproductively active. These data coincide with evidence that the wild population may be in decline. Captive snakes, had low plasma levels of corticosterone with males displaying a peak in plasma testosterone levels during breeding. Furthermore, we compared body condition between the free-living and captive snakes from Guam and free-living individuals captured from their native range in Australia. Male and female free-living snakes from Guam exhibited significantly reduced body condition compared to free-living individuals from Australia. We suggest that during the study period, free-living brown tree snakes on Guam were living under stressful conditions, possibly due to overcrowding and overexploitation of food resources, resulting in decreased body condition and suppressed reproduction. 相似文献