The Nilgiri tahr Nilgiritragus hylocrius is an Endangered species of mountain ungulate endemic to the Western Ghats of India, a biodiversity hotspot. Habitat fragmentation, hunting and a restricted range are the major threats to this species. Although several surveys have assessed the species’ status, a population estimate based on a scientifically robust method is needed. We used the double-observer method to estimate the population of the Nilgiri tahr in the Anamalai Tiger Reserve, a protected area in the Western Ghats. We walked 257 km of transects across the Reserve, covering 36 grassland blocks (i.e. clusters of montane grasslands that were relatively separate from each other). We counted a minimum of 422 individuals in 28 groups, and estimated the tahr population in the study area to be 510 individuals (95% CI 300–858) in 35 groups. The male:female ratio was 0.71 and the young:female ratio was 0.56. Comparing our estimate with previous surveys suggests that the Nilgiri tahr population in Anamalai Tiger Reserve is stable. We found the double-observer survey method to be appropriate for population estimation and long-term monitoring of this species, and make recommendations for improved field protocols to facilitate the implementation of the method in the tropical mountains of the Western Ghats. Our findings suggest that the Reserve harbours 20–25% of the global population of the Nilgiri tahr, highlighting the area's importance for the conservation of this species.

The random encounter model, a method for estimating animal density using camera traps without the need for individual recognition, has been developed over the past decade. A key assumption of this model is that cameras are placed randomly in relation to animal movements, requiring that cameras are not set only at sites thought to have high animal traffic. The aim of this study was to define a correction factor that allows the random encounter model to be applied in photo-trapping surveys in which cameras are placed along tracks to maximize capture probability. Our hypothesis was that applying such a correction factor would compensate for the different rates at which lynxes use tracks and the surrounding area, and should thus improve the estimates obtained with the random encounter model. We tested this using data from a well-known Iberian lynx Lynx pardinus population. Firstly, we estimated Iberian lynx densities using a traditional camera-trapping design followed by spatially explicit capture–recapture analyses. We estimated the differential use rate for tracks vs the surrounding area using data from a lynx equipped with a GPS collar, and subsequently calculated the correction factor. As expected, the random encounter model overestimated densities by 378%. However, the application of the correction factor improved the estimate and reduced the error to 16%. Although there are limitations to the application of the correction factor, the corrected random encounter model shows potential for density estimation of species for which individual identification is not possible.

Demographic monitoring is required in threatened species management, yet effective and efficient monitoring is challenging for species that are difficult to capture or susceptible to capture stress. One possible monitoring approach for such species is non-invasive genetic sampling with capture–recapture methods (genetic capture–recapture). We evaluated the performance of genetic capture–recapture in a challenging model system, monitoring the threatened Sonoran pronghorn Antilocapra americana sonoriensis. In an effort to determine the best (i.e. efficient, accurate, precise, cost-effective) method for abundance estimation, we used simulations to examine the optimal genetic capture–recapture faecal sampling design for this population. We simulated encounter histories for 100–300 individuals, with 0.33–3.33 samples/individual/session, in 1–3 sampling sessions. We explored trade-offs between sample size, number of sessions and multi-session (MARK) versus single-session (capwire) closed capture–recapture abundance estimators, and an accurate and precise estimate. We also compared the cost between the genetic capture–recapture approaches and current aerial monitoring methods. Abundance was biased positively in capwire and negatively in MARK. Bias increased and precision decreased with fewer samples/individual/session. Annual genetic capture–recapture monitoring cost was nearly twice the cost of aerial surveys, although genetic capture–recapture methods provided much higher precision. However at the current estimated abundance (c. 200), the same level of precision achieved with aerial methods can be obtained by collecting 0.75 samples/individual in a single session, for an annual cost saving of > USD 4,000. This approach of comparing estimator performance and cost can easily be applied to other systems and is a useful evaluation for managers to implement prior to designing capture–recapture studies.

The Eurasian lynx Lynx lynx population in the Carpathian Mountains is considered to be one of the best preserved and largest in Europe and hence is a source for past and current reintroduction projects in central Europe. However, its status in Slovakia has been reported to the European Commission on the basis of hunters´ reports and expert estimates that have never been validated by a robust scientific approach. We conducted the first camera-trapping surveys to estimate the density of Eurasian lynx in Slovakia by means of spatial capture–recapture models in two reference areas during 2011–2015. We estimated population density per 100 km2 of suitable lynx habitat (posterior SD) as 0.58 ± SD 0.13 independent individuals (adults and subadults) in the Štiavnica Mountains and 0.81 ± SD 0.29 in Veľká Fatra National Park and surroundings. These are the lowest densities estimated using spatial capture–recapture models so far reported for the species, suggesting the lynx population in Slovakia is below carrying capacity. We suspect that low densities may be attributable to undetected human-caused mortality. Our results imply that official game statistics are substantially overestimated. Moreover, the lynx population in Slovakia may not be at favourable conservation status as required by the EU Habitats Directive. We therefore call for a thorough assessment of the density and trend of the Slovak Carpathian lynx population, and the establishment of a scientifically robust monitoring system.

Information on the abundance of tigers Panthera tigris is essential for effective conservation of the species. The main aim of this study was to determine the status of tigers in Chitwan National Park, Nepal, including the Churia hills, using a camera-trap based mark–recapture abundance estimate. Camera traps (n = 310) were placed in an area of 1,261 km2 from 20 January to 22 March 2010. The study area was divided into three blocks and each block was trapped for 19–21 days, with a total effort of 3,582 man-days, 170 elephant-days and 4,793 camera-trap nights. The effectively camera-trapped area was 2,596 km2. Camera stations were located 1.5–2 km apart. Sixty-two tigers (age ⩾ 1.5 years), comprising 15 males, 41 females and six of unidentified sex, were identified from 344 photographs. The heterogeneity model Mh (jackknife) was the best fit for the capture history data. A capture probability ( $\hat P$ ) of 0.05 was obtained, generating a population estimate ( $\hat N$ ) of 125 ± SE 21.8 tigers. The density of tigers in the area, including Churia and Barandabhar (buffer zone forest linked with mid hill forest), was estimated to be 4.5 ± SE 0.35 tigers per 100 km2, using a Bayesian spatially explicit capture–recapture model in SPACECAP. Our study showed the use of Churia by tigers and we therefore conclude that the Chitwan tiger population serves as a source to maintain tiger occupancy of the larger landscape that comprises Chitwan National Park, Parsa Wildlife Reserve, Barandabhar buffer zone, Someswor forest in Nepal and Valmiki Tiger Reserve in India.

Effective conservation of rare carnivores requires reliable estimates of population density for prioritizing investments and assessing the effectiveness of conservation interventions. We used camera traps and capture–recapture analysis to provide the first reliable abundance and density estimates for the common leopard Panthera pardus and clouded leopard Neofelis nebulosa in Manas National Park, India. In 57 days of camera trapping, with a total of 4,275 camera-trap days, we photo-captured 27 individually identified common leopards (11 males, 13 females and three unidentified), and 16 clouded leopards (four males, five females and seven unidentified). The abundance estimates using the M h jackknife and Pledger model M h were 47.0 and 35.6, respectively, for the common leopard, and 21.0 and 25.0, respectively, for the clouded leopard. Density estimates using maximum likelihood spatially-explicit capture–recapture were 3.4 ± SE 0.82 and 4.73 ± SE 1.43 per 100 km2 for the common and clouded leopards, respectively. Spatially-explicit capture–recapture provided more realistic density estimates compared with those obtained from conventional methods. Our data indicates that camera trapping using a capture–recapture framework is an effective tool for assessing population sizes of cryptic and elusive carnivores such as the common and clouded leopards. The study has established a baseline for the long-term monitoring programme for large carnivores in Manas National Park.

Methods that accurately estimate animal abundance or density are crucial for wildlife management. Although numerous techniques are available, there have been few comparisons of the precision and cost-effectiveness of different approaches. We assess the precision and cost of three methods for estimating densities of the Endangered Grevy's zebra Equus grevyi. We compare distance sampling and photographic capture–recapture, and a new technique, the random encounter model (REM) that uses camera-trap encounter rates to estimate density. All three methods provide comparable density estimates for Grevy's zebra and are preferable to the common practice of raw counts. Photographic capture–recapture is the most precise and line-transect distance sampling the least precise. Line transects and photographic capture–recapture surveys are cost-effective in the first year and REM is most cost-effective in the long-term. The methods used here for Grevy's zebra may be applied to other rangeland ungulates. We suggest that for single species monitoring programmes in which individuals can be identified, photographic capture–recapture surveys may be the preferred method for estimating wildlife abundances. When encounter rates are low, distance sampling lacks the precision of the other methods but its cost advantage may make it appropriate for long-term or multi-species monitoring programmes. The REM is an efficient and precise method of estimating densities but has high initial equipment costs. We believe REM has the potential to work well for many species but it requires independent estimates of animal movements and group size.

Robust disease burden estimates are important for decision-making concerning introduction of new vaccines. Dengue is a major public health problem in the tropics but robust disease burden estimates are lacking. We conducted a two-sample, capture–recapture study in the largest province in Cambodia to determine disease under-recognition to the National Dengue Surveillance System (NDSS). During 2006–2008, community-based active surveillance for acute febrile illness was conducted in 0- to 19-year-olds in rural and urban areas combined with testing for dengue virus infection. Of 14 354 individuals under active surveillance (22 498 person-seasons), the annual incidence ranged from 13·4 to 57·8/1000 person-seasons. During the same period, NDSS incidence rates ranged from 1·1/1000 to 5·7/1000, which was 3·9- to 29·0-fold lower than found in the capture–recapture study. In hospitalized cases, the rate of under-recognition was 1·1- to 2·4-fold. This study shows the substantial degree of under-recognition/reporting of dengue and that reported hospitalized cases are not a good surrogate for estimating dengue disease burden.

Asiatic lions Panthera leo persica, once confined to the 1,883 km2 Gir Protected Area in Gujarat, India, have in the past 2 decades colonized the adjacent Girnar forest, coastal scrub and agro-pastoral areas covering c. 10,000 km2. In May 2008 the Government of Gujarat declared 180 km2 of the sacred Girnar forests a Wildlife Sanctuary. We obtained data on location, age, gender and group composition of lions in Girnar Wildlife Sanctuary from opportunistic sightings during March–May 2008 and from systematic surveys in April 2008 (six surveys of 3–4 days each), totalling 81 lions on 40 occasions. Of the 81 sightings 43% were in the recruitment age group. Adult sex ratio was 0.87 males : 1 female. In the systematic survey we made 26 sightings of nine individuals, identified from their vibrissae patterns and permanent body markings, and used these for population estimation using a capture–recapture analysis. The population estimate using the best fit null model Mo was 10 ± SE 1.2 giving an adult lion density of 5.6 ± SE 0.7 per 100 km2. Population viability analysis emphasized the importance of immigrants for the persistence of this small population. One immigrant in 2 years reduced the probability of extinction by 16%. Conservation of the habitat matrix to the south-east of the Sanctuary, used as a corridor for movement between Girnar and Gir, by declaring it an eco-sensitive zone would facilitate the long-term survival of the Girnar lion population.

In comparison with the Neotropical big cats, jaguar (Panthera onca L.) and puma (Felis concolor L.), medium and small felids are poorly studied. Furthermore, studying wild felids in forest habitats is extremely difficult using direct methods given that most species are principally nocturnal and secretive (Gittleman 1996). Indirect methods are therefore particularly important, e.g. radio-telemetry (Emmons 1987, 1988; Konecny 1989, Ludlow & Sunquist 1987) or camera trapping (Maffei et al. 2002, Trolle & Kéry 2003). Using systematic camera trap surveys, we compare the population density of ocelots (Felis pardalis L.) across five Bolivian dry-forest sites with different habitat types and/or annual rainfall regimes (Table 1). We hypothesize that ocelot densities will decline as rainfall declines. In addition, we estimate the population of ocelots in the 34 400-km2 Kaa-Iya del Gran Chaco National Park. Finally, we describe and evaluate additional ecological information provided by camera trapping: activity patterns relative to seasonality and moon phase, sex ratios, ranging patterns and relative abundance compared with sympatric felids.

Annual local survival of the garden dormouse Elyomis quercinus, a small, hibernating rodent, was studied by Cormack–Jolly–Seber models. The survival rates differed significantly between the 4 years of the study; the average rate was 0.38 (95% confidence interval: 0.25–0.52). Survival rates were not significantly different between sexes. Because all garden dormice were captured after weaning, pre-weaning survival could not be estimated. After weaning, the annual survival rates did not differ between age cohorts. In order to find out which phases within the annual cycle were more prone to mortality, survival was studied on a bimonthly scale as well. Survival during hibernation was estimated to be close to unity, while survival during the active phase of life in summer was considerably lower. The winter temperatures of the study years were similar to the long-year average; thus garden dormice were well adapted to these average conditions. Although hibernation is energetically challenging, it is not necessarily accompanied by increased mortality, as found in other studies focusing on survival during hibernation.

Let W be a sum of Bernoulli random variables and Uλ a Poisson random variable having the same mean λ = EW. Using the Stein-Chen method and suitable couplings, general upper bounds for the variational distance between W and Uλ are given. These bounds are applied to problems of occupancy, using sampling with and without replacement and Pólya sampling, of capture-recapture, of spacings and of matching and ménage.