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1.
Madagascar ranks as one of the world’s top extinction hotspots because of its high endemism and high rate of habitat degradation. Global climate phenomena such as El Niño Southern Oscillations may have confounding impacts on the island’s threatened biota but these effects are less well known. We performed a demographic study of Propithecus edwardsi, a lemur inhabiting the eastern rainforest of Madagascar, to evaluate the impact of deforestation, hunting, and El Niño on its population and to re-evaluate present endangerment categorization under the IUCN. Over 18 years of demographic data, including survival and fecundity rates were used to parameterize a stochastic population model structured with three stage classes (yearlings, juveniles, and adults). Results demonstrate that hunting and deforestation are the most significant threats to the population. Analysis of several plausible scenarios and combinations of threat revealed that a 50% population decline within three generations was very likely, supporting current IUCN classification. However, the analysis also suggested that changing global cycles may pose further threat. The average fecundity of lemurs was over 65% lower during El Niño years. While not as severe as deforestation or hunting, if El Niño events remain at the current high frequency there may be negative consequences for the population. We suggest that it is most critical for this species continued survival to create more protected areas, not only to thwart hunting and deforestation, but also to give this endangered lemur a better chance to recover from and adapt to altered climate cycles in the future.  相似文献   

2.
Community Based Wildlife Management (CBWM) has been suggested as a conservation strategy in response to bushmeat hunting in the Udzungwa Mountains within the Eastern Afromontane biodiversity hotspot. The feasibility of CBWM based on meat cropping was therefore evaluated in New Dabaga/Ulangambi Forest Reserve (NDUFR). Comparison of relative wildlife densities with West Kilombero Scarp Forest Reserve, which is subject to only low hunting pressure, indicate that most relevant populations are severely depleted (Cephalophus monticola, C. harveyi and C. spadix, Potamochoerus larvatus) and hence that sustainable harvesting currently is not possible in NDUFR. Records of catch from hunters in the villages surrounding NDUFR indicate that bushmeat is of relatively low importance in terms of use and contribution to protein intake. Proximity to NDUFR and secondarily population size in the different villages is positively correlated with hunting intensity and depletion of wildlife. Comparisons between hunters and non-hunters in terms of wealth measures show that hunting is linked to poverty and low protein intake. An estimation of maximum sustainable harvest in NDUFR reveals that CBWM only has limited capacity to reduce these causes of hunting, maintain the communities’ interest and offset the opportunity costs of conservation. Results of this study suggest that conservation efforts in NDUFR should focus on protecting wildlife against exploitation instead of encouraging use and dependence through CBWM. Supporting efforts should attempt to facilitate a complete shift to domestic sources of meat, by increasing the number of domestic animals in the poorest part of the population.  相似文献   

3.
Capybaras (Hydrochoerus hydrochaeris) are the world’s largest rodent. Free-living populations are commercially harvested for their meat and leather in Colombia, Venezuela and Argentina; however, there is concern that legal and illegal harvesting is not sustainable. Since capybaras are considered an economic resource, there have been several attempts to explore the effect of different hunting strategies on its population dynamics. Two previous population models have been developed with this goal; however neither included capybara social behavior that may affect population dynamics. We developed an age-structured, density-dependent model of capybara herd dynamics to explore the demographic consequences of different hunting strategies. We then added infanticide and female reproductive suppression to explore the demographic consequences of such behavior. We conducted five different simulations and used ANOVA to estimate the effect of hunting females, hunting males, hunting both males and females, and the independent effects of reproductive suppression and infanticide on population size after 50 years. Our model suggests that suppression has the largest effect on population size, followed by hunting females and males hunting, female hunting, male hunting and infanticide. Thus, to develop more realistic harvesting models, managers should determine the degree of reproductive suppression and the frequency of infanticide by males.  相似文献   

4.
Recently, European wild rabbit (Oryctolagus cuniculus) populations have undergone a sharp decline that may be exacerbated by hunting. We investigate the effects of the timing of hunting on the conservation of wild rabbit using a model for rabbit population dynamics. Scenarios with different hunting rates and age strategies were simulated for different population qualities. We interviewed hunters to ascertain the degree to which they would accept a change in the timing of hunting. We also investigated the hunting pressure applied by hunters and its relationship with rabbit abundance. Modelling results indicate that the current hunting season has the greatest impact on rabbit abundance. Hunting in late spring optimises hunting extraction while conserving rabbit populations. When the rabbit population quality is low the effects of age strategies and the timing of hunting are less important than the effect of the hunting rate applied. Almost half the hunters would agree to policy changes. More than 75% of hunters implemented self-imposed hunting restrictions to improve rabbit populations, that were more frequently applied in high rabbit abundance areas. Therefore, changing the timing of hunting and increasing the participation of hunters in low abundance areas could optimise both the exploitation and the conservation of wild rabbit populations in southwestern Europe.  相似文献   

5.
Large mammal faunas in tropical forest landscapes are widely affected by habitat fragmentation and hunting, yet the environmental determinants of their patterns of abundance remain poorly understood at large spatial scales. We analysed population abundance and biomass of 31 species of medium to large-bodied mammal species at 38 Atlantic forest sites (including three islands, 26 forest fragments and six continuous forest sites) as related to forest type, level of hunting pressure and forest fragment size using ANCOVAs. We also derived a novel measure of mammal conservation importance for each site based on a “Mammalian Conservation Priority index” (MPi) which incorporates information on species richness, population abundance, body size distribution, conservation status, and forest patch area. Mammal abundance was affected by hunting pressure, whereas mammalian biomass of which was largely driven by ungulates, was significantly influenced by both forest type and hunting pressure. The MPi index, when separated into its two main components (i.e. site forest area and species-based conservation index Ci), ordered sites along a gradient of management priorities that balances species-focused and habitat-focused conservation actions. Areas with the highest conservation priority were located in semi-deciduous forest fragments, followed by lowland forests. Many of these fragments, which are often embedded within large private landholdings including biofuel and citrus or coffee crops, cattle ranches and pulpwood plantations, could be used not only to comply with environmental legislation, but also enhance the prospects for biodiversity conservation, and reduce edge effects and hunting.  相似文献   

6.
New Guinea’s mammalian fauna consists of a unique assemblage of relatively small sized (0.5-13.5 kg) marsupial mammals, the hunting of which provides a major source of protein for local communities. However, the impact of hunting and the influence of the marsupial life-history strategies on the sustainability of hunting are unknown. Anthropological studies of subsistence hunting and published life-history data for Australasian marsupial mammals were quantitatively reviewed to determine the major sources of game and annual harvest, and estimate intrinsic rates of population increase (rmax) and population densities. These data were used to estimate extraction versus maximum sustainable production (MSP) and make a preliminary estimate of the sustainability of hunting. There were significant negative relationships between increasing body size and decreasing rmax and decreasing population densities, which were further influenced by phylogeny and diet, and appear very similar to relationships found for placental mammals in Afrotropical and Neotropical forests. The estimated biomass of mid-sized marsupial mammals (923 kg/km2) in Papua New Guinea is also comparable with densities of placental mammals in other evergreen tropical forests. Intrinsic rates of increase ranged from 0.28 for tree-kangaroos (Macropodidae) and 0.29 for cuscus (Phalangeridae), up to 5.14 for bandicoots/echymipera (Peroryctidae). Estimated population densities ranged from 0.4-4.0 animals/km2 for long-beaked echidna (Zaglossus sp.) to 150-340 animals/km2 for ringtails (Pseudocheridae). Extraction rates of game in three studies averaged 23.5 ± 9.9 kg/km2/year, with cuscus and bandicoot species numerically comprising the main game, although cuscus are the most important source of protein. Rates of extraction in Papua New Guinea versus rates of production demonstrate that long-beaked echidna, tree-kangaroos and cuscus are likely to be hunted unsustainably. In contrast hunting of bandicoots and ringtails was lower than maximum production levels, and the high intrinsic rate of increase of bandicoots means that they can potentially provide a sustainable source of protein, in preference to scarcer and intrinsically slower breeding species.  相似文献   

7.
Several predator species at risk of extinction in Southwestern Europe are dependent on the population density of European wild rabbits Oryctolagus cuniculus. Rabbit populations in the region, however, have recently undergone dramatic decreases in population density, which may be exacerbated by hunting. Current hunting policies set the autumn-winter season, just before the start of rabbit reproduction, as the main hunting season, and previous theoretical models have estimated that the current hunting season may have the greatest negative impact on rabbit abundance and should be changed. We utilised a model for rabbit population dynamics to determine the effects of the timing of hunting during two seasons, summer and autumn, on the tendency of rabbit populations to be over-harvested and on the number of rabbits hunted. This model included field estimates of age- and sex-selection biases of hunting by shotgun. Scenarios with different hunting rates and sex- and age-selection probabilities of hunting were simulated for populations with different turnover levels and with and without compensatory mortality mechanisms. Field estimations showed that hunting in summer was juvenile-biased whereas autumn hunting was juvenile- and male-biased. In contrast to previous findings, our modelling results suggested that hunting in autumn may be the most conservative option for harvesting of rabbit populations, since these populations were more prone to be over-harvested during the summer. The differences between the two seasons in number of rabbits hunted were dependent on population dynamics and hunting sex- and age-selection probabilities. Our findings suggest that altering of current hunting policies would not optimise the exploitation or conservation of wild rabbit populations, but that the latter may be improved by some changes in the timing of hunting.  相似文献   

8.
The severely depleted bowhead whale Balaena mysticetus has failed to recover from overexploitation during the 18th and 19th centuries in the Eastern Arctic. Although commercial whaling for bowheads ended in this region about 1915, bowhead whaling by native people has continued until recently in parts of the Eastern Arctic. Low-level but persistent hunting by Inuit (Eskimos) may have inhibited bowhead population increase. Two natural mortality factors can be documented—ice entrapment and predation by killer whales Orcinus orca. There is little direct evidence of ice-related mortality but a strong circumstantial argument that ice conditions affect survival. Killer whales are known to prey on most species of large whales, and we believe bowhead whales and right whales Eubalaena glacialis are especially vulnerable. The bowhead's apparent failure to recover in the Eastern Arctic may be due to a combination of continued low-level hunting, habitat instability, and predation. Complete protection from all forms of hunting is necessary to ensure the bowhead's survival. Environmental disturbances due to industrial development in the Arctic may have direct and indirect impact on bowhead habitat and behaviour, creating an urgent need for further study.  相似文献   

9.
We apply an age- and stage-structured model incorporating varying harem sizes, paternal care and infanticide to examine the effect of hunting on sustainability of populations. Compared to standard carnivore and herbivore models, these models produce different outcomes for sustainable offtake when either adults, or adult males are harvested. Larger harem size increases sustainable offtake whereas paternal care and infanticide lowers it. Where males are monogamous, populations are vulnerable to male offtake, regardless of paternal care. Surprisingly, an incidental take of 10% of other age-sex-classes has very little effect on these findings. Indiscriminate (subsistence) hunting of all age-sex classes has a dramatic effect on certain populations. Applying these behavior-sensitive models to tourist hunting in the Selous Game Reserve, Tanzania, we find that across the Reserve hunting quotas were generally set at sustainable rates except for leopard (Panthera pardus). In certain hunting blocks within the Reserve, however, quotas for eland (Taurotragus oryx), hartebeest (Alcelaphus buselaphus), lion (Panthera leo), reedbuck (Redunca arundinum), sable antelope (Hippotragus niger), warthog (Phacochoerus aethiopicus) and waterbuck (Kobus ellipsiprymnus) are set at unsustainably high rates. Moreover, particular blocks are consistently awarded high quotas. Behaviorally sensitive models refine predictions for population viability, specify data required to make predictions robust, and demonstrate the necessity of incorporating behavioral ecological knowledge in conservation and management.  相似文献   

10.
《Biological conservation》1987,42(4):303-311
The effects of predation and habitat deterioration produced by rats, cats, dogs, pigs, goats, burros and cattle, which have been introduced over the last two centuries to the Galapagos archipelago, have reduced the dark-rumped petrel Pterodroma phaeopygia population so that it is now in danger of extinction. By controlling rat numbers through poisoning, and by protecting the nesting colony from other predator and pest species through hunting, petrel breeding success in the Cerro Pajas colony, Floreana Island, has been increased. Preliminary studies indicate that immediate conservation efforts are also needed and are being initiated for at least two other petrel populations. Continued predator control is essential to halt further petrel population declines and to allow their numbers to recuperate.  相似文献   

11.
The red-footed booby, Sula sula, has been hunted in the Cocos (Keeling) Islands, eastern Indian Ocean, since first settlement in 1827. Formerly present throughout the islands, an estimated 30,000 pairs now breed only on isolated and uninhabited North Keeling Island. Despite legislative protection, illegal hunting for food remains a major conservation threat. Informants estimated that 2000-3000 birds are killed in most years and possibly as many as 10,000 in some years. Analysis of nest count data collected between 1985 and 2002 to assess long-term population trends showed no evidence of decline in nesting density. There was large inter-annual variation with substantial fluctuations which tended to be greater following significant cyclonic events. These results indicate that the level of illegal harvest during the study period has not negatively impacted the booby nesting population. Future management of seabird harvesting requires improved knowledge on the population's capacity to sustain harvesting, together with increased enforcement activity to control illegal harvest, and enhanced education programs to encourage change in community attitudes.  相似文献   

12.
Biological control is proposed as an ecological strategy to manage the threat of invasive plants, especially in natural areas. To pursue this strategy, we need to know that the host specificity criteria used to evaluate ecological risk with deliberate introduction of an exotic insect for biocontrol are sufficient to predict potential impact on native species. Host specificity is defined by adult feeding and oviposition preferences and larval development. One way to evaluate the criteria is to re-examine case histories where ecological effects are recorded, such as that of Rhinocyllus conicus Frölich. This flower head weevil, released in North America in 1968 to control exotic thistles like Musk thistle (Carduus nutans L), is now reducing seed production by multiple native North American thistle species (Cirsium spp.), and local population density of Platte thistle (Cirsium canescens Nutt.). We hypothesized that host specificity of R. conicus has changed since pre-release testing, providing an explanation for the unexpected magnitude of the documented ecological effects. Instead, when we re-tested host specificity of weevils naturalized over 28 generations, we found that host specificity has not changed. Naturalized adults of R. conicus showed strong feeding and oviposition preference for Musk thistle over Platte thistle. In addition, larval development by these weevils was faster and more successful (to larger size) on Musk thistle than on Platte thistle. Thus, our results indicate that a change in host specificity cannot explain the unexpectedly large build-up of R. conicus and significant ecological effect on Platte thistle. We conclude that accurate prediction of the potential level of impact on native host plants in the field requires further ecological information in addition to host specificity.  相似文献   

13.
The impact of hunting on wildlife is a complex phenomenon which varies in space and across time, and yet limited knowledge is available on it. This is especially the case of the indirect effects of hunting on the behaviour of target as well as non-target species. Here we analyze how hunting affected the spatial behaviour of 62 radiocollared roe deer (Capreolus capreolus) in a protected area adjacent to areas where hunting with hounds (target species: wild boar and hares) and stalking with rifles from high seats without dogs (target species: roe deer) were permitted during the hunting season. Our results showed that hunting caused a significant increase in the home range size of monitored deer, as well as a “reserve effect”, whereby roe deer used the protected area as a refuge from hunters. These behavioural responses were significant only at times when hunting with hounds was conducted, even though roe deer was not the target species of this technique. Reactions to the perceived risk of predation varied among age and sex classes, with yearling being more sensitive and using the protected area more than adults. As shown in our study, hunting harassment provoked by drives with hounds significantly affects the behaviour of non-target species. Therefore, the use of long-legged hounds represents a variable that should be carefully evaluated by wildlife managers in their management plans and conservation policies, especially when endangered or vulnerable species are present.  相似文献   

14.
Effective conservation of exploited species requires an understanding of the motivations experienced by resource users. When use is illegal, it can be particularly difficult to distinguish users from non-users. The attitudes of local people are critical to conservation success, because they interact with social circumstances to determine behaviour. In this study we explore the factors influencing inferred poaching behaviour of the Critically Endangered saiga antelope (Saiga tatarica) in six communities in three countries of the former Soviet Union. We show that local people have a good understanding of the species’ status and positive attitudes towards its conservation, regardless of their household’s inferred poaching status. Poaching is a low prestige occupation, and our analyses suggest that it is carried out by poor, unemployed households who have the means to hunt. These results are consistent for all villages. However we find important regional differences in hunting behaviour, linked to saiga population density and migration patterns, which have implications for the likely effectiveness of different conservation strategies. Community-based interventions are more likely to be appropriate in Russia, where saigas are present year-round and hunting is more subsistence based, than in the strongly seasonal Kazakhstan populations where economies of scale require organised poaching by fewer households. This case study illustrates the complex linkages between attitudes, social circumstances and behaviour in resource user behaviour, and highlights both the consistencies and differences in drivers of poaching between locations at a range of spatial scales.  相似文献   

15.
Most tropical forest landscapes are modified by humans, but the effects of these changes on rural hunting patterns and hunted vertebrate populations remain poorly understood. We investigated subsistence hunting patterns across a highly heterogeneous landscape mosaic in the Brazilian Amazon, where hunters from three villages had access to primary forest, active and fallow agricultural fields, and active and fallow Eucalyptus plantations. Landscape composition and the areas used by hunters were defined using a remote-sensing approach combined with mapping. We quantified hunting effort accounting for the availability and spatial distribution of each habitat. Overall, 71% of the kills were sourced in primary forest, but hunting in primary forest, which was often combined with other extractive activities (such as Brazil nut harvesting), yielded the lowest catch-per-unit-effort of all habitats. Hunting effort per unit area was highest in fallow fields, followed by primary forest, and both of these habitats were over-represented within village hunting catchments when compared to the composition of the available landscape. Active and fallow fields sourced a limited number of species known to be resilient to hunting, but hunting had additional benefits through crop-raider control. In contrast, hunting pressure in active and fallow plantations was low, despite a high catch-per-unit-effort, presumably because there were limited additional benefits from visiting these habitats. These results indicate that large-scale tree plantation and forest regeneration schemes have limited conservation potential for large vertebrates, as they support few forest specialists and fail to attract hunters away from primary forest.  相似文献   

16.
Hunting is the major driver of large mammal decline in Central African forests. In slowly reproducing species even low hunting pressure leaves spatial gradients with wildlife density increasing with distance from transport routes and human settlements. Park management can use this pattern formation to identify sources of threats, but also to discriminate between different threat scenarios, such as the impact of subsistence vs. commercial hunting. We conducted an ape survey in the mountainous Moukalaba Doudou National Park, Gabon, to evaluate whether potential population gradients would emanate from the three human population centers in the region or the villages surrounding the park. Using generalized linear modeling we found hill slope as a good predictor of ape nest occurrence probability and the distance to human population centers a better predictor of ape nest density and ape nest group size than distance to villages. In fact ape nest density was three times lower at the park borders close to the human population centers than in the park’s interior. The results indicate that Moukalaba’s ape population is more impacted by commercial than subsistence hunting and suggest that park management should focus conservation efforts on the human population centers. We conclude that in particular for slowly reproducing species geographic information on wildlife population gradients are of additional value for guiding protected area management. The hunting impact on those species might be easily underestimated, if derived only from market surveys or transport route controls, where they are only rarely found.  相似文献   

17.
The Eurasian woodcock Scolopax rusticola is a migratory bird of major importance for hunting, which is susceptible to habitat loss and the stochastic effects of severe winter weather. Conservation issues mostly concerned regulation of hunting, but the efficiency of hunting-free reserves has never been investigated. We studied causes of mortality and survival probabilities of 98 radio-tagged woodcocks in a reserve with no hunting and in an adjoining hunting area in Brittany (France). Predation, mostly by mammalian predators on fields at night, was similar among adults and yearlings, while hunting mortality was more important in yearlings. Overall winter survival probabilities were 0.86 ± SE 0.07 in adults and 0.63 ± SE 0.07 in yearlings. Survival probabilities of both age classes increased as birds spent more time in the reserve. Equality of predation in both reserve and hunting areas suggests an additive mortality due to hunting over the winter. Population matrix models predicted that such low survival probabilities cannot sustain long term viable populations. These results call for caution in the harvesting of woodcock populations wintering in western France and could be a forewarning of a decline. The regulation of hunting by setting bag limits or reducing the length of shooting seasons, or the creation of reserves might be appropriate tools for the sustainable management of woodcock populations.  相似文献   

18.
Causes of mortality were described for 245 radio-marked Eurasian lynx (Lynx lynx) in five different Scandinavian study areas. Furthermore, the survival rates and the population growth rates were estimated for three of the study areas where 202 lynx were followed for a total of 314 radio-years. The main causes of mortality in adult Eurasian lynx in all our study areas were overwhelmingly anthropogenic, with starvation, vehicle collisions, intra- and interspecific killing and disease only having a minor role. The mean mortality rates for adults increased from 2% to 17% when hunting and poaching were included, i.e., an increase by a factor of eight. This in turn had a large impact on population growth rates, which changed from more than a 20% annual increase to only a 2-4% when hunting and poaching were included. Poaching accounted for 46% of the mortality in adult lynx. Poaching and legal harvest appear to be primarily motivated by conflicts; lynx depredation on semi-domestic reindeer in northern Scandinavia, competition with hunters for roe deer in southern Scandinavia, and depredation on free-ranging domestic sheep in all Norway. The lowest poaching rate was found in the Hedmark study area in Norway, which also had a high legal harvest. The poaching rate was higher in one of the Swedish study areas (Sarek) where legal hunting was lower than in other areas. On the other hand, both the poaching rate and the legal harvest were high in the Akershus/Østfold study area in Norway. Thus, there does not seem to be a simple relationship between an increased legal harvest and decreased poaching as is commonly expected. The most important conservation actions are to combat poaching through both law enforcement and measures designed to increase tolerance.  相似文献   

19.
Illegal hunting poses a dual threat to large carnivores through direct removal of individuals and by prey depletion. We conducted a camera-trapping survey in the Namdapha National Park, north-east India, conducted as part of a programme to evaluate carnivore and prey species abundance. Clouded leopard (Neofelis nebulosa) was the only large carnivore detected by camera-trapping. Indirect evidences indicated the presence of the wild dog (Cuon alpinus) and leopard (Panthera pardus), however, there was no evidence of tigers (Panthera tigris), suggesting their possible extinction from the lower elevation forests. Of the major ungulate prey species, sambar (Cervus unicolor) and wild pig (Sus scrofa) were the only large prey detected, while the Indian muntjac (Muntiacus muntjak) was the only small prey species detected. Relative abundances of all species were appreciably lower than estimates from other tropical forests in south-east Asia. We suspect that illegal hunting may be the cause for the low carnivore and prey species abundance. An ongoing community-based conservation programme presents an opportunity to reduce local people’s dependence on hunting by addressing their socio-economic needs and for using their skills and knowledge of the landscape for wildlife conservation. However, long-term wildlife monitoring is essential to assess the efficacy of the socio-economic interventions in bringing about wildlife recovery.  相似文献   

20.
Interviews with hunters and collection of skulls indicate that Trichechus inunguis occurs throughout the region of the Amazon River estuaries from Amapá to the mainland of Pará, including Ilha de Marajó and islands on its Atlantic coast. T. manatus has a disjunct distribution in Brazil, apparently occurring both on the coast of Amapá north of Cabo Norte and in the Rio Mearim (Maranhão) as well as further to the southwest; it seems to have been exterminated from the Atlantic coast of Pará and is absent from the Marajó region. Continued subsistence hunting can best be controlled by destruction of illegal camboas (fence-like traps) which catch manatees at high tide. Areas deserving study are the coast and inland lakes of eastern Amapá, the only place in the world where two sirenian species might still be found in sympatry or immediate proximity, and the lower Rio Mearim in Maranhão, which may still contain a sizable population of T. manatus. Ecological studies in these areas should have particular relevance to hypotheses of sirenian evolutionary interactions, and manatee reserves should be established in both areas.  相似文献   

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