Evaluating persistence and its predictors in a West African carnivore community (original) (raw)
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Ecological Applications, 2019
Carnivore communities face unprecedented threats from humans. Yet, management regimes have variable effects on carnivores, where species may persist or decline in response to direct or indirect changes to the ecosystem. Using a hierarchical multispecies modeling approach, we examined the effects of alternative management regimes (i.e., active vs. passive enforcement of regulations) on carnivore abundances and group sizes at both species and community levels in the Masai Mara National Reserve, Kenya. Alternative management regimes have created a dichotomy in ecosystem conditions within the Reserve, where active enforcement of regulations maintains low levels of human disturbance in the Mara Triangle and passive enforcement of regulations in the Talek region permits multiple forms of human disturbance. Our results demonstrate that these alternative management regimes have variable effects on 11 observed carnivore species. As predicted, some species, such as African lions and bat-eared foxes, have higher population densities in the Mara Triangle, where regulations are actively enforced. Yet, other species, including black-backed jackals and spotted hyenas, have higher population densities in the Talek region where enforcement is passive. Multiple underlying mechanisms, including behavioral plasticity and competitive release, are likely causing higher black-backed jackals and spotted hyena densities in the disturbed Talek region. Our multispecies modeling framework reveals that carnivores do not react to management regimes uniformly, shaping carnivore communities by differentially producing winning and losing species. Some carnivore species require active enforcement of regulations for effective conservation, while others more readily adapt (and in some instances thrive in response) to lax management enforcement and resulting anthropogenic disturbance. Yet, high levels of human disturbance appear to be negatively affecting the majority of carnivores, with potential consequences that may permeate throughout the rest of the ecosystem. Community approaches to monitoring carnivores should be adopted as single species monitoring may overlook important intra-community variability.
A number of recent studies have suggested that large carnivores are rapidly disappearing in West Africa, including in protected areas (PAs). The extent of this extinction process, however, is poorly known. Here, we quantify the extinction of three large carnivore species (Panthera leo (lion), Acinonyx jubatus (cheetah) and Lycaon pictus (wild dog)) in 41 West and Central African PAs by comparing historical and current data of occurrence. We found that lions have gone (near-) extinct in 23 out of the 38 PAs (63%) where they historically occurred and that extinction is significantly more pronounced in West (15 extinctions out of 18 historical occurrence, 64%) than in Central Africa (8/20, 40%). Cheetahs have disappeared from 11 out of 15 PAs (73% of site extinction). Wild dogs persist in only one PA in West Africa and two in Central Africa out of a total of 31 historical occurrences (90% of site extinction). For all three species combined, the number of extinctions in PAs in West Africa (33 out of 39 historical occurrences, i.e. 85% of site extinction) is significantly higher than in Central African PAs (29/45, i.e. 64%). Carnivore populations persist outside PAs in that latter region. Our study shows that PAs with remaining lion populations are significantly larger than those with extinct populations. However, we found that the human population density around PAs is not a good predictor of lion extinction. We suggest that the presence of mobile pastoralists may better explain the extinction pattern of large predators, and we recommend developing indicators of the pastoralism pressure to test that hypothesis.
Tropical Conservation Science, 2015
A number of recent studies have suggested that large carnivores are rapidly disappearing in West Africa, including in protected areas (PAs). The extent of this extinction process, however, is poorly known. Here, we quantify the extinction of three large carnivore species (Panthera leo (lion), Acinonyx jubatus (cheetah) and Lycaon pictus (wild dog)) in 41 West and Central African PAs by comparing historical and current data of occurrence. We found that lions have gone (near-) extinct in 23 out of the 38 PAs (63%) where they historically occurred and that extinction is significantly more pronounced in West (15 extinctions out of 18 historical occurrence, 64%) than in Central Africa (8/20, 40%). Cheetahs have disappeared from 11 out of 15 PAs (73% of site extinction). Wild dogs persist in only one PA in West Africa and two in Central Africa out of a total of 31 historical occurrences (90% of site extinction). For all three species combined, the number of extinctions in PAs in West Africa (33 out of 39 historical occurrences, i.e. 85% of site extinction) is significantly higher than in Central African PAs (29/45, i.e. 64%). Carnivore populations persist outside PAs in that latter region. Our study shows that PAs with remaining lion populations are significantly larger than those with extinct populations. However, we found that the human population density around PAs is not a good predictor of lion extinction. We suggest that the presence of mobile pastoralists may better explain the extinction pattern of large predators, and we recommend developing indicators of the pastoralism pressure to test that hypothesis.
PLoS ONE, 2012
Protected areas (PAs) are a cornerstone of global efforts to shield wildlife from anthropogenic impacts, yet their effectiveness at protecting wide-ranging species prone to human conflict -notably mammalian carnivores -is increasingly in question. An understanding of carnivore responses to human-induced and natural changes in and around PAs is critical not only to the conservation of threatened carnivore populations, but also to the effective protection of ecosystems in which they play key functional roles. However, an important challenge to assessing carnivore communities is the often infrequent and imperfect nature of survey detections. We applied a novel hierarchical multi-species occupancy model that accounted for detectability and spatial autocorrelation to data from 224 camera trap stations (sampled between October 2006 and January 2009) in order to test hypotheses about extrinsic influences on carnivore community dynamics in a West African protected area (Mole National Park, Ghana). We developed spatially explicit indices of illegal hunting activity, law enforcement patrol effort, prey biomass, and habitat productivity across the park, and used a Bayesian model selection framework to identify predictors of site occurrence for individual species and the entire carnivore community. Contrary to our expectation, hunting pressure and edge proximity did not have consistent, negative effects on occurrence across the nine carnivore species detected. Occurrence patterns for most species were positively associated with small prey biomass, and several species had either positive or negative associations with riverine forest (but not with other habitat descriptors). Influences of sampling design on carnivore detectability were also identified and addressed within our modeling framework (e.g., road and observer effects), and the multi-species approach facilitated inference on even the rarest carnivore species in the park. Our study provides insight for the conservation of these regionally significant carnivore populations, and our approach is broadly applicable to the robust assessment of communities of rare and elusive species subject to environmental change.
Detecting declines of apex carnivores and evaluating their causes: An example with Zambian lions
Biological Conservation, 2014
Large carnivores are in rapid global decline, with a broad array of consequences for the ecosystems they inhabit. To efficiently detect and address these declines requires unbiased and precise demographic data. Unfortunately, the characteristics that make large carnivores extinction-prone also pose serious challenges to obtaining these data. Rapid survey methods exist, but provide only relative measures of abundance, cannot detect declines before they become large, and provide little or no information about the causes of decline. African lions (Panthera leo) are declining throughout their range, making accurate monitoring of remaining populations urgent. We provide statistically rigorous estimates of population size, trends, survival rate and age-sex structure from Zambia's South Luangwa lion population from 2008 to 2012, just prior to cessation of hunting in 2013. Mark-recapture models fit to data from intensive monitoring of 210 individual lions in 18 prides and 14 male coalitions indicated a declining population, low recruitment, low sub-adult and adult male survival, depletion of adult males, and a senescing adult female population. Trophy hunting was the leading cause of death, with 46 males harvested. Based on these data we recommend continuing the hunting ban at least to 2016 to allow recovery, with substantially reduced quotas, age-limits, and effective trophy monitoring mandated thereafter should hunting resume. Similar data from intensive monitoring of key Zambian lion populations is required to evaluate effects of the hunting ban and provide management guidance. Effectively integrating intensive long-term monitoring and rapid survey methods should be a priority for future management and monitoring of carnivore species.
African Journal of Ecology, 2018
Effective management of threatened wildlife, particularly large carnivores, depends on a sound understanding of their spatial distribution and status in relationship to environmental or anthropogenic impacts. Here we analyse data from spoor surveys to investigate occurrence across a multiple-use landscape in the Tarangire-Simanjiro ecosystem in northern Tanzania for four taxa of African large carnivores: lions (Panthera leo), hyaenas (spotted hyaenas (Crocuta crocuta) and striped hyaenas (Hyaena hyaena) combined), cheetahs (Acinonyx jubatus) and leopards (P. pardus). We analysed our data using occupancy modeling, explicitly accounting for detectability, to identify associations with environmental and anthropogenic variables. Overall occurrence was estimated at 0.85 (SE = 0.06) for hyaena, 0.82 (SE = 0.15) for cheetah, 0.55 (SE = 0.10) for lion and 0.61 (SE = 0.21) for leopard. Lion occurrence was negatively associated with distance to park boundary. Hyaena occurrence was positively associated with human population density and negatively associated with bushland, while cheetah and leopard occurrences were positively associated with grassland. These results suggest that lions may be more vulnerable to human impacts than other species, while hyaenas may benefit from vicinity to humans. Our study demonstrates the value of spoor-based occupancy surveys for understanding distribution and habitat-use of secretive large carnivores.
Estimates of carnivore densities in a human-dominated agricultural matrix in South Africa
Oryx
Populations of carnivore species outside protected areas may be of considerable importance for conservation, as many protected areas do not provide sufficient space for viable populations. Data on carnivore population sizes and trends are often biased towards protected areas, and few studies have examined the role of unprotected areas for carnivore conservation. We used camera-trapping data and spatial capture–recapture models to estimate population densities for four sympatric carnivores: the African leopard Panthera pardus, spotted hyaena Crocuta crocuta, brown hyaena Parahyaena brunnea and African civet Civettictis civetta in Platjan, a predominantly agricultural, mixed land-use system, South Africa. Mean densities per 100 km2 for the leopard were 2.20 (95% CI 1.32–3.68) and 2.18 (95% CI 1.32–3.61) for left and right flank data, respectively; spotted hyaena, 0.22 (95% CI 0.06–0.81); brown hyaena, 0.74 (95% CI 0.30–1.88); and African civet 3.60 (95% CI 2.34–5.57; left flanks) and ...
Long-term trends in carnivore abundance using distance sampling in Serengeti National Park, Tanzania
Journal of Applied Ecology, 2011
1. Carnivores can have critical impacts on ecosystems, provide economic value through tourism and are often important flagships. However, their biological traits (e.g. low density, cryptic colouration and behaviour) make them difficult to monitor and hence wildlife managers rarely have access to reliable information on population trends, and long-term information at the community level is almost completely lacking. 2. We use data from transect counts in the Serengeti ecosystem in Tanzania to examine trends in abundance for seven co-existing carnivore species. Distance-based transect counts between 2002 and 2005 are compared with adjusted data from fixed-width transect counts across the same area in 1977 and 1986. 3. Distance-based methods provided density indices for the seven most commonly seen carnivores: lion Panthera leo, spotted hyaena Crocuta crocuta, golden jackal Canis aureus, black-backed jackal Canis mesomelas, cheetah Acinonyx jubatus, side-striped jackal Canis audustis and bat-eared fox Otocyon megalotis. Detection curves were used to correct estimates from earlier fixed-width transect counts. 4. Trend analyses detected significant declines in densities of golden and black-backed jackal and bat-eared fox, but found no significant changes in spotted hyaena, lion, cheetah and side-striped jackal. 5. Overall, despite wide confidence intervals, we show that distance-based data can be used effectively to detect long-term trends and provide critical information for conservation managers. Power analysis demonstrated that for the most frequently seen species, spotted hyaena, golden jackal and lion, abrupt declines of up to 20% may be detectable through long-term monitoring; however, for the remaining species, declines of 50% may only be detected half the time. 6. Synthesis and applications. Distance methods provide a tool for rapid counts and monitoring of several species of carnivores simultaneously in suitable habitats and can be combined with historical fixed-width transect counts to test for changes in density. The method can provide key information to managers on long-term population trends and sudden abrupt changes in population size across a carnivore community.
Oryx, 2011
Accurate assessment of carnivore population status is frequently hindered by insufficient distribution data. For northern South Africa we address this deficit by mapping new records from landscape-scale sign surveys, questionnaire interviews, problem animal records and camera trapping. The black-backed jackal Canis mesomelas and caracal Caracal caracal remain common and widespread. Ranges of the serval Leptailurus serval and brown hyaena Hyaena brunnea were much larger than previous estimates, reducing the risk of simultaneous extirpation across all occupied locations. The proportion of range area occupied was larger for several species, notably the leopard Panthera pardus, cheetah Acinonyx jubatus and serval. We conclude that the serval continues to recover from historical threats and is expanding into new areas. A larger brown hyaena range and less fragmented pattern of occurrence probably confers greater resilience to threats than was suggested by previous data. Reduced extinctio...