Photographic database informs management of conflict tigers

The increasing interface between people and wildlife contributes to human–wildlife conflict in many conservation landscapes. In India animals suspected to be involved in conflict are often captured and translocated to different locations or zoological parks. A key concern in the capture of so-called problem animals has been the identification of individuals involved in conflict. The Wildlife Conservation Society (WCS) India Program, in collaboration with research partners, has aided government officials in this matter through its research on tigers in the Malenad Tiger Landscape, south-west India. As part of a research programme initiated in 1991, WCS India has formulated a protocol for individual identification of tigers, based on their stripe patterns. Using pattern-matching software that aids quick and reliable identification of tigers from photographs (Hiby et al., 2009, Biology Letters, 5, 383-386, a photographic database has been developed, with > 750 individually identified tigers from 60 protected areas totalling > 38,000 km2, and elsewhere, in India. Ancillary information on home ranges, activity patterns and sociobiology of conflict-tigers provides a unique opportunity for informed management of the species. This long-term, ongoing study is funded by the Department of Science and Technology and the Department of Biotechnology of the Government of India, Vision Group on Science & Technology of the Government of Karnataka, and the Wildlife Conservation Society, New York. Two recent cases of human–tiger conflict in the Malenad Tiger Landscape exemplify the utility of this database and long-term monitoring for conflict mitigation. One incident, on 27 December 2013, involved the loss of human life in Bandipur National Park, and the other, on 1-2 January 2014, involved the killing of cattle in a village adjoining Nagarahole National Park. In the latter incident a dead cow was used as bait to capture the tiger involved. In the incident in Bandipur photographs from camera traps set up in the area of conflict were matched to individuals in the database. One individual was identified in nine of the 15 photographs obtained and, as the location of conflict was well beyond its home range, it was identified as the conflict individual and was subsequently captured. The tigers from both incidents have been transferred to a nearby zoo. The Forest Department debated relocation of the individuals but this was not pursued. Both of the tigers involved in these incidents had been photographed previously multiple times. The tiger in Bandipur had been photographed over the last 5 years and was probably an old individual past its prime. The tiger in Nagarahole was 2–3 years old and had only been photographed in the previous year. The distances between the locations of previous photographs and the location of conflict were 4–8 km for the tiger in Bandipur and 35 km for the tiger in Nagarahole. The observation of the Nagarahole individual with another male in two photographs suggests that this individual was dispersing from its natal home range to establish a breeding territory. Nagarahole and Bandipur National Parks have high tiger densities (10-15 tigers per 100 km2 ) with c. 20% of the population lost annually to mortality and emigration. It is likely that the Nagarahole individual was emigrating from the reserve. The infrequency of dispersal events, particularly in human-dominated landscapes such as the Malenad Tiger Landscape, suggests that the removal of the Nagarahole tiger, a potential long-distance disperser, may have detrimental effects on the long-term population viability of tigers in this landscape. In contrast, the removal of the Bandipur tiger will probably have negligible effects on the population, although any relocation into an existing tiger population would be likely to cause further conflict (Athreya et al.,2011, Conservation Biology, 25, 133–141). Mitigation of conflict is frequently ad hoc, with management authorities pressurized into quick but often ineffective action. In these two contrasting examples, alternative actions could have had very different consequences. In areas where data on the age, reproductive status and ranging patterns of conflict animals are available, this information should be used to direct conflict mitigation strategies such that they are maximally effective whilst inflicting least harm on species viability

Bayesian inference in camera trapping studies for a class of spatial capture-recapture models

We develop a class of models for inference about abundance or density using spatial capture-recapture data from studies based on camera trapping and related methods. The model is a hierarchical model composed of two components: a point process model describing the distribution of individuals in space (or their home range centers) and a model describing the observation of individuals in traps. We suppose that trap- and individual-specific capture probabilities are a function of distance between individual home range centers and trap locations. We show that the models can be regarded as generalized linear mixed models, where the individual home range centers are random effects. We adopt a Bayesian framework for inference under these models using a formulation based on data augmentation. We apply the models to camera trapping data on tigers from the Nagarahole Reserve, India, collected over 48 nights in 2006. For this study, 120 camera locations were used, but cameras were only operational at 30 locations during any given sample occasion. Movement of traps is common in many camera-trapping studies and represents an important feature of the observation model that we address explicitly in our application

On a Dhole trail: examining ecological and anthropogenic correlates of Dhole habitat occupancy in the Western Ghats of India

Although they play a critical role in shaping ecological communities, many threatened predator species are data-deficient. The Dhole Cuon alpinus is one such rare canid with a global population thought to be < 2500 wild individuals. We assessed habitat occupancy patterns of dholes in the Western Ghats of Karnataka, India, to understand ecological and anthropogenic determinants of their distribution and habitat-use. We conducted spatially replicated detection/non-detection surveys of dhole signs along forest trails at two appropriate scales: the entire landscape and a single wildlife reserve. Landscape-scale habitat occupancy was assessed across 38,728 km2 surveying 206 grid cells of 188-km2 each. Finer scale habitat-use within 935 km2 Bandipur Reserve was studied surveying 92 grid cells of 13-km2 km each. We analyzed the resulting data of dhole signs using likelihood-based habitat occupancy models. The models explicitly addressed the problematic issue of imperfect detection of dhole signs during field surveys as well as potential spatial auto-correlation between sign detections made on adjacent trail segments. We show that traditional ‘presence versus absence’ analyses underestimated dhole habitat occupancy by 60% or 8682 km2 [naïve  =  0.27; ≏ ψL (SE) =  0.68 (0.08)] in the landscape. Addressing imperfect sign detections by estimating detection probabilities [ˆpt(L) (SE)  =  0.12 (0.11)] was critical for reliable estimation. Similar underestimation occurred while estimating habitat-use probability at reserve-scale [naïve  =  0.39; ˆψs (SE) =  0.71 (0.06)]. At landscape scale, relative abundance of principal ungulate prey primarily influenced dhole habitat occupancy. Habitat-use within a reserve, however, was predominantly and negatively influenced by anthropogenic disturbance. Our results are the first rigorous assessment of dhole occupancy at multiple spatial scales with potential conservation value. The approach used in this study has potential utility for cost-effectively assessing spatial distribution and habitat-use in other species, landscapes and reserves

How many tigers Panthera tigris are there in Huai Kha Khaeng Wildlife Sanctuary, Thailand? An estimate using photographic capture-recapture sampling

We used capture-recapture analyses to estimate the density of a tiger Panthera tigris population in the tropical forests of Huai Kha Khaeng Wildlife Sanctuary, Thailand, from photographic capture histories of 15 distinct individuals. The closure test results (z=0.39, P=0.65) provided some evidence in support of the demographic closure assumption. Fit of eight plausible closed models to the data indicated more support for model Mh, which incorporates individual heterogeneity in capture probabilities. This model generated an average capture probability p^=0.42 and an abundance estimate of N^(SE^[N^])=19 (9.65) tigers. The sampled area of Â(W)(SE^[Â(W)])=477.2 (58.24) km2 yielded a density estimate of D^(SE^)[D^])=3.98 (0.51) tigers per 100 km2. Huai Kha Khaeng Wildlife Sanctuary could therefore hold 113 tigers and the entire Western Forest Complex c. 720 tigers. Although based on field protocols that constrained us to use sub-optimal analyses, this estimated tiger density is comparable to tiger densities in Indian reserves that support moderate prey abundances. However, tiger densities in well-protected Indian reserves with high prey abundances are three times higher. If given adequate protection we believe that the Western Forest Complex of Thailand could potentially harbour >2,000 wild tigers, highlighting its importance for global tiger conservation. The monitoring approaches we recommend here would be useful for managing this tiger population

Etude de la germination de cinq provenances de Tamarindusindica L. en conditions de stress hydrique au Sénégal

Ce présent travail se propose d’évaluer le comportement germinatif de cinq provenances de tamarinier (Tamarindus indica L.) dans des conditions de stress  hydrique. Six concentrations croissantes 0 ; - 1,4 ; - 2,8 ; - 4,2 ; - 5,6 ; -7 bar de polyéthylène glycol (PEG 6000) ont été testées. Les résultats ont montré une  variabilité de la germination de l’espèce en fonction de l’intensité du stress et de la provenance. Le seuil critique de germination des provenances du tamarinier est  de -7 bar. La provenance Sakkal de la zone sahélienne s’est montrée plus tolérante au stress hydrique avec un taux de germination de 2% en conditions de stress  sévère. Toutefois, ces faibles résultats sont imputables aux conditions de conservation des graines. Ces informations sur l'écologie et la physiologie de la  germination du tamarinier sont vitales, non seulement pour comprendre les variations génétiques des différentes populations de tamarinier au Sénégal, mais aussi pour développer des stratégies pour la conservation de la biodiversité et la restauration des forêts tropicales.Mots clés : Germination, provenances, Tamarindus indica L., stress hydrique, Sénégal

Tigers on trails: occupancy modeling for cluster sampling

Occupancy modeling focuses on inference about the distribution of organisms over space, using temporal or spatial replication to allow inference about the detection process. Inference based on spatial replication strictly requires that replicates be selected randomly and with replacement, but the importance of these design requirements is not well understood. This paper focuses on an increasingly popular sampling design based on spatial replicates that are not selected randomly and that are expected to exhibit Markovian dependence. We develop two new occupancy models for data collected under this sort of design, one based on an underlying Markov model for spatial dependence and the other based on a trap response model with Markovian detections. We then simulated data under the model for Markovian spatial dependence and fit the data to standard occupancy models and to the two new models. Bias of occupancy estimates was substantial for the standard models, smaller for the new trap response model, and negligible for the new spatial process model. We also fit these models to data from a large-scale tiger occupancy survey recently conducted in Karnataka State, southwestern India. In addition to providing evidence of a positive relationship between tiger occupancy and habitat, model selection statistics and estimates strongly supported the use of the model with Markovian spatial dependence. This new model provides another tool for the decomposition of the detection process, which is sometimes needed for proper estimation and which may also permit interesting biological inferences. In addition to designs employing spatial replication, we note the likely existence of temporal Markovian dependence in many designs using temporal replication. The models developed here will be useful either directly, or with minor extensions, for these designs as well. We believe that these new models represent important additions to the suite of modeling tools now available for occupancy estimation in conservation monitoring. More generally, this work represents a contribution to the topic of cluster sampling for situations in which there is a need for specific modeling (e.g., reflecting dependence) for the distribution of the variable(s) of interest among subunits

Chest CT features of patients under investigation for Covid-19 pneumonia in a Ghanaian tertiary hospital: a descriptive study

Background: Coronavirus disease 2019 (COVID-19) has since December 2019 become a problem of global concern. Due to the virus’ novelty and high infectivity, early diagnosis is key to curtailing spread. The knowledge and identification of chest Computerized Tomography (CT) features in Patients Under Investigation (PUI) for the disease would help in its management and containment. Objectives: To describe the chest CT findings of PUI for COVID-19 pneumonia referred to the Department of Radiology of the Korle Bu Teaching Hospital; as well as to determine the relationship between symptom onset and severity of the chest CT findings. Methods: The study was retrospective and included 63 PUI for COVID-19 referred to the Department between 11th April, 2020 and 10th June, 2020, for non-enhanced chest CT imaging. Clinical data were obtained from patients’ records and Reverse Transcriptase–Polymerase Chain Reaction (RT-PCR) results were acquired after the CT evaluation. Results: The mean age in years was 51.1±19.9 SD. More males (52.8%) than females (47.2%) tested positive for COVID-19 and the age range for positive cases was 7 months to 86 years, with a mean of 53.2±21 SD years. Common features of COVID-19 pneumonia were bilateral posterior basal consolidations, Ground Glass Opacities (GGO) and air bronchograms. Findings were worse in patients scanned 5–9 days after onset of symptoms. Conclusion: Adequate knowledge of chest CT features of COVID-19 pneumonia, proves a valuable resource in triaging of symptomatic patients and consequent containment of the disease in the hospital setting