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.

Data on the distribution and population size of the Near Threatened Tibetan antelope Pantholops hodgsonii are necessary to protect this species. Ground-based count surveys are usually carried out from a long distance to avoid disturbing the sensitive animals, and on calving grounds or along migration routes where they are seasonally concentrated. This can result in underestimation of population sizes if terrain features obstruct the view and high concentrations of animals make estimating numbers difficult. Here we test the efficacy of unmanned aerial vehicles (UAVs) for gathering population data for the Tibetan antelope. We conducted the study south of a known calving ground, at the foot of Sewu Snow Mountain, in the Chang Tang National Nature Reserve, China. The UAV did not appear to disturb the animals and resulted in more accurate counts than ground-based observations. A total of 23,063 Tibetan antelopes were identified in twelve orthoimages derived from c. 4,000 aerial photographs. In the first flight area 7,671 females and 4,353 calves were identified (proportion of calves: 36.2%). In the second flight area 7,989 females and 3,050 calves were identified (proportion of calves: 27.6%). Two flights over the same area revealed the direction and speed of moving Tibetan antelope groups. Image resolution, which can be controlled with flight planning, was an important factor in determining the animals’ visibility in the photos. We found that UAV-based surveys outperformed ground-based surveys, and that larger UAVs are preferable for this application.

We conducted community interviews and field surveys to determine the distribution and population of the Endangered Shortridge's capped langur Trachypithecus shortridgei, and the threats to the species, in the Dulong and Nu River valleys of north-western Yunnan Province, China. We found that c. 19 groups of T. shortridgei reside in the Dulong valley, mostly located in the southern portion of the valley. According to interview and observational records in the Gaoligong Mountains to the west of the Nu River, 12 individuals and no groups were observed. Family groups consist of one adult male, 2–3 adult females and up to five young. We estimate the population of T. shortridgei in China to be c. 250–370 individuals. Threats to the species include habitat loss and poaching. We suggest several measures to conserve T. shortridgei, such as a review of the Gaoligong National Nature Reserve management strategy, and increasing engagement, education, inclusion of local people in forest management, and the consistency of enforcement.

Despite > 60 years of conservation in Uganda's national parks the populations of lions and spotted hyaenas in these areas have never been estimated using a census method. Estimates for some sites have been extrapolated to other protected areas and educated guesses have been made but there has been nothing more definitive. We used a lure count analysis method of call-up counts to estimate populations of the lion Panthera leo and spotted hyaena Crocuta crocuta in the parks where reasonable numbers of these species exist: Queen Elizabeth Protected Area, Murchison Falls Conservation Area and Kidepo Valley National Park. We estimated a total of 408 lions and 324 hyaenas for these three conservation areas. It is unlikely that other conservation areas in Uganda host > 10 lions or > 40 hyaenas. The Queen Elizabeth Protected Area had the largest populations of lions and hyaenas: 140 and 211, respectively. It is estimated that lion numbers have declined by 30% in this protected area since the late 1990s and there are increasing concerns for the long-term viability of both species in Uganda.

We assessed the abundance and distribution of the greater one-horned or Indian rhinoceros Rhinoceros unicornis in all its potential habitats in Nepal, using block counts. In April 2011 5,497 km were searched in 3,548 elephant-hours over 23 days. The validity of the block count was assessed by comparing it with counts obtained from long-term monitoring using photographic identification of individual rhinoceroses (ID-based), and estimates obtained by closed population sighting–mark–resighting in the 214 km2 of Chitwan National Park. A total of 534 rhinoceroses were found during the census, with 503 in Chitwan National Park (density 1 km−2), 24 in Bardia National Park (0.28 km−2) and seven in Suklaphanta Wildlife Reserve (0.1 km−2). In Chitwan 66% were adults, 12% subadults and 22% calves, with a female : male ratio of 1.24. The population estimate from sighting–mark–resighting was 72 (95% CI 71–78). The model with different detection probabilities for males and females had better support than the null model. In the Sauraha area of Chitwan estimates of the population obtained by block count (77) and ID-based monitoring (72) were within the 95% confidence interval of the estimate from sighting–mark–resighting. We recommend a country-wide block count for rhinoceroses every 3 years and annual ID-based monitoring in a sighting–mark–resighting framework within selected subpopulations. The sighting–mark–resighting technique provides the statistical rigour required for population estimates of the rhinoceros in Nepal and elsewhere.

Identifying individuals through time can provide information on population size, composition, survival and growth rates. Identification using photographs of distinctive physical characteristics has been used in many species to replace conventional marker tagging. We evaluated photographic records over 7 years of Vulnerable whale sharks Rhincodon typus, at an aggregation in the Seychelles, for estimation of population size and structure. We collected 11,681 photographs of which only 1,149 were suitable for comparison using semi-automated matching software (I3S) of individual spot patterns behind the gills. Photo-identification showed that there was considerable loss of marker tags and enabled an estimation of the rate of tag loss. The combination of photo-identification with marker tagging identified a total of 512 individual sharks over 2001–2007. Of these, there were 115 resightings in subsequent years with two sharks identified in 2001 resighted 5 years later in 2006 and another shark sighted in 2001 resighted in 2007. Estimates of abundance using conventional open mark–recapture models for 2004–2007 were 348–488 sharks (95% confidence interval), with a high level of entry into the population by itinerants. Annual apparent survival probability was 0.343–0.781 over 2004–2007, with an average annual recapture probability of 0.201. These results are the first to suggest a highly transient population of whale sharks around the Seychelles, indicating that international or at least regional-scale conservation approaches are required.

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 = 0.42 and an abundance estimate of = 19 (9.65) tigers. The sampled area of = 477.2 (58.24) km2 yielded a density estimate of = 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.

A large deviations principle (LDP), demonstrated for occupancy problems with indistinguishable balls, is generalized to the case in which balls are distinguished by a finite number of colors. The colors of the balls are chosen independently from the occupancy process itself. There are r balls thrown into n urns with the probability of a ball entering a given urn being 1/n (i.e. Maxwell-Boltzmann statistics). The LDP applies with the scale parameter, n, tending to infinity and r increasing proportionally. The LDP holds under mild restrictions, the key one being that the coloring process by itself satisfies an LDP. This includes the important special cases of deterministic coloring patterns and colors chosen with fixed probabilities independently for each ball.

Distance sampling is a common and increasingly used method of estimating animal abundance in conservation and management programmes. The precision of a distance sampling survey can be estimated from the field data, but accuracy can only be evaluated by comparison with the true population size. For wild mammal populations, such opportunities are rare. The high-density badger Meles meles population at Woodchester Park in Gloucestershire, U.K. has been routinely and intensively live-trapped for the past 30 years. The estimates of abundance based on mark–recapture analyses of the live-trapping data provided a reliable baseline against which to evaluate distance sampling for a badger population. A distance sampling survey was carried out in autumn 2002 by using spotlighting along line transects. Owing to the impractical nature of spotlighting in closed habitats, such as woodland, surveys were conducted in open habitat only. A radio-tracking study provided behavioural data that were used to estimate the proportion of the population available for sampling in open habitats. This was incorporated as a multiplier into the DISTANCE analysis. The estimate of abundance from distance sampling was 76 badgers (% CV=42.2), using a multiplier based on radio-tracking data from autumn only. When the multiplier was derived from radio-tracking data from across the whole year, based on a larger sample of tracked badgers, the distance sampling abundance estimate was 77 badgers (% CV=25.9). These compared favourably to the mark–recapture estimate of 68 badgers (% C.V=7.4). The lack of precision in the distance sampling density estimate was largely owing to the inclusion of the multiplier. Distance sampling combined with data on habitat use can produce reliable estimates of badger abundance in areas of medium to high density, particularly in landscapes of primarily open habitat.

Estimates of roosting habitat availability and population size using unbiased sampling regimes are completely lacking for any bat species. The use of conspicuous and accessible roosts in the developing, rolled leaves of Heliconia and Calathea plants by Thyroptera tricolor (Spix's disc-winged bat) provided an ideal opportunity to address this need. To assess roost availability and population size, the number of occupied and unoccupied leaves and bats in known areas in an area of lowland rain forest in north-eastern Costa Rica were quantified in 1998–99. A high density of leaves was available on any given day (mean: 43 leaves ha−1), but the density of roost leaves was low (mean: 2.5 leaves ha−1), corresponding with a low occupancy rate of 5.7 or 12% based on different methods of estimation. Developing leaves were available for 8–16 h in the preferred size range of leaves used by T. tricolor, and a maximum of 28–60 h, depending on the plant species. Using closed-population mark–recapture models, the 5.69-ha study area supported 261 individuals over a 4-mo period in 1998, corresponding to a density of 43 bats ha−1. These results have important implications for the results of studies on bat community structure and rarity, and for the behaviour and ecology of T. tricolor.

Data on the populations of larval and pupal stages of Aedes africanus, an important sylvan vector of arboviruses, were collected from tree-holes which are its natural breeding sites in forests. Comparable data were also simultaneously collected from bamboo pots stationed in the Zika Forest to simulate the natural breeding sites. Survivorship curves and time-specific life-tables were constructed. It was observed that the immature stages of A. africanus in both tree-holes and bamboo pots suffered very high mortality rates (an average of 91% in tree-holes and 83.2% in bamboo pots). It was further observed that mortality rates varied monthly. The survivorship curves constructed for the immature stages collected on a daily basis tended to show that a large proportion of the mortality rate was confined to the early instar stages, but the survivorship curves based on the combined data for the 2 years indicated constant mortality rates for all the stages. The high mortality rates of the immature stages of A. africanus appear to be attributed to predation by larvae of Toxorhynchites brevipalpis, with which it shares the same breeding places.