Hierarchical Multi-Species Modeling of Carnivore Responses to Hunting, Habitat and Prey in a West African Protected Area

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

Protected Areas in Tropical Africa: Assessing Threats and Conservation Activities

Numerous protected areas (PAs) have been created in Africa to safeguard wildlife and other natural resources. However, significant threats from anthropogenic activities and decline of wildlife populations persist, while conservation efforts in most PAs are still minimal. We assessed the impact level of the most common threats to wildlife within PAs in tropical Africa and the relationship of conservation activities with threat impact level. We collated data on 98 PAs with tropical forest cover from 15 countries across West, Central and East Africa. For this, we assembled information about local threats as well as conservation activities from published and unpublished literature, and questionnaires sent to long-term field workers. We constructed general linear models to test the significance of specific conservation activities in relation to the threat impact level. Subsistence and commercial hunting were identified as the most common direct threats to wildlife and found to be most prevalent in West and Central Africa. Agriculture and logging represented the most common indirect threats, and were most prevalent in West Africa. We found that the long-term presence of conservation activities (such as law enforcement, research and tourism) was associated with lower threat impact levels. Our results highlight deficiencies in the management effectiveness of several PAs across tropical Africa, and conclude that PA management should invest more into conservation activities with long-term duration.Additional co-authors: Jef Dupain, Atanga Ekobo, Manasseh Eno-Nku, Gilles Etoga, Takeshi Furuichi, Sylvain Gatti, Andrea Ghiurghi, Chie Hashimoto, John A. Hart, Josephine Head, Martin Hega, Ilka Herbinger, Thurston C. Hicks, Lars H. Holbech, Bas Huijbregts, Hjalmar S. Kühl, Inaoyom Imong, Stephane Le-Duc Yeno, Joshua Linder, Phil Marshall, Peter Minasoma Lero, David Morgan, Leonard Mubalama, Paul K. N'Goran, Aaron Nicholas, Stuart Nixon, Emmanuelle Normand, Leonidas Nziguyimpa, Zacharie Nzooh-Dongmo, Richard Ofori-Amanfo, Babafemi G. Ogunjemite, Charles-Albert Petre, Hugo J. Rainey, Sebastien Regnaut, Orume Robinson, Aaron Rundus, Crickette M. Sanz, David Tiku Okon, Angelique Todd, Ymke Warren, Volker Somme

Carnivore species detected during the camera trap survey in Mole National Park, Ghana, and estimated mean occurrence (<i>ψ</i>) and detection (<i>p</i>) probabilities and covariate effects on occurrence.

<p>The proportion of 224 sampling sites at which carnivore species were detected reflects observation data, whereas <i>ψ</i> and <i>p</i> are model-averaged estimates from the multi-species hierarchical mixture model (means and standard deviations from posterior probability distributions for species-specific parameters). Site covariates of occurrence are shown for cases where the posterior probability distribution from the full model for the corresponding species-specific coefficient indicated a potential effect (i.e., posterior mass not concentrated at 0; distributions are given in Appendix S3).</p>a<p>Scientific names in Table S1.</p>b<p>Direction of effect indicated as either positive (+) or negative (−) association of species occurrence probability with the particular covariate. For the different prey biomass covariates, only the strongest effect is indicated.</p

Posterior probability summaries of hyper-parameters for mean community-level effects of hypothesized site covariates on carnivore occurrence (<i>α</i> and <i>δ</i> coefficients) and detection (<i>β</i> coefficients).

<p>Posterior mean, standard deviation (SD) and 95% credible interval (CI) were estimated from the full model, while the corresponding inclusion probability from model selection using a mixture model is also shown (representing the posterior probability of that covariate effect being included in the best model). Posterior distributions for these hyper-parameters as well as species-level parameters are given in Appendix S3.</p>*<p>The two prey indices derived from patrol data were not included in the final mixture model as they were considered redundant to (but less informative than) the comparable short-term prey indices derived from camera trap data (based on results of the full model and a preliminary mixture model).</p

Model-predicted carnivore responses to the three site covariates included in the best occurrence model.

<p>Predicted marginal probabilities of carnivore occurrence relative to variation in the index of small prey biomass, distance from riverine forest, and distance from park edge (all values standardized). Species are: African civet (solid black), caracal (dashed red), Gambian mongoose (dotted green), large-spotted genet (dot-dash blue), leopard (dashed light blue), marsh mongoose (dot-dash purple), side-striped jackal (solid yellow), spotted hyena (dashed grey), white-tailed mongoose (dotted black; scientific names and details of model selection are given in the text).</p

Posterior model probabilities for the top 11 models that had 90% of the posterior support across all candidate models for community-level effects on carnivore occurrence (<i>ψ</i>) and detection (<i>p</i>), as estimated from the mixture modeling approach to model selection (53 additional models appeared in the posterior sample but all with probabilities <0.01).

<p>Posterior model probabilities for the top 11 models that had 90% of the posterior support across all candidate models for community-level effects on carnivore occurrence (<i>ψ</i>) and detection (<i>p</i>), as estimated from the mixture modeling approach to model selection (53 additional models appeared in the posterior sample but all with probabilities <0.01).</p

Camera-trap locations

<p>(<b>n = 224</b>) <b>and indices of patrol effort, hunting activity, habitat, and prey biomass in Mole National Park, Ghana.</b> (A) Index of law enforcement patrol effort (i.e., “protection”) calculated as the density of patrol pathways covered between Oct. 2006 and May 2008 (also showing the location of villages within 10 km of the park boundary); (B) NDVI, the normalized difference vegetation index (from MODIS/Terra sensor) summed over the study period (i.e., integrated NDVI, Oct. 2006 – Jan. 2009); (C) Index of illegal hunting activity detected by law enforcement patrols (observations per unit patrol effort); (D) Patrol-based, multi-season index of biomass for prey species weighing less than 18 kg (standardized by patrol effort). No data were obtained in the white areas within the park boundary.</p

Proportion of protected areas with conservation activities between 1990 and 1999 across different African regions.

<p>The number of protected areas with available information on presence and absence of any conservation activity (research, tourism and law enforcement guards) over the considered period were in total 105.</p

Regional distribution of the protected areas (PAs) in tropical Africa considered in the analyses.

<p>The regions are coloured in different grey scale colours. Light grey represents West Africa, including 54 protected areas; medium grey represents Central Africa, including 31 protected areas; dark grey represents East Africa, including 14 protected areas. On the left-side bottom corner a MODIS NDVI image of Africa, with a red quadrant highlighting the tropical area considered in the study.</p