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Camera Traps (camera + trap)
Selected AbstractsCarnivore biodiversity in Tanzania: revealing the distribution patterns of secretive mammals using camera trapsANIMAL CONSERVATION, Issue 2 2010N. Pettorelli Abstract Biodiversity monitoring is critical to assess the effectiveness of management activities and policy change, particularly in the light of accelerating impacts of environmental change, and for compiling national responses to international obligations and agreements. Monitoring methods able to identify species most likely to be affected by environmental change, and pinpoint those changes with the strongest impacts, will enable managers to target efforts towards vulnerable species and significant threats. Here we take a new approach to carnivore monitoring, combining camera-trap surveys with ecological niche factor analysis to assess distribution and patterns of habitat use of mammalian carnivore assemblages across northern Tanzania. We conducted 11 surveys over 430 camera-trap stations and 11 355 trap-days. We recorded 23 out of 35 carnivore species known to occur in Tanzania and report major extensions to the known distribution of the bushy-tailed mongoose Bdeogale crassicauda, previously thought to be rare. Carnivore biodiversity tended to be higher in national parks than in game reserves and forest reserves. We explored habitat use for seven species for which we had sufficient information. All species tended to be found near rivers and southern Acacia commiphora woodlands (except one mongoose species), and avoided deciduous shrubland, favouring deciduous woodland and/or open grassland. All species tended to avoid croplands suggesting that habitat conversion to agriculture could have serious implications for carnivore distribution. Our study provides a first example where camera-trap data are combined with niche analyses to reveal patterns in habitat use and spatial distribution of otherwise elusive and poorly known species and to inform reserve design and land-use planning. Our methodology represents a potentially powerful tool that can inform national and site-based wildlife managers and policy makers as well as international agreements on conservation. [source] Evaluating capture,recapture population and density estimation of tigers in a population with known parametersANIMAL CONSERVATION, Issue 1 2010R. K. Sharma Abstract Conservation strategies for endangered species require accurate and precise estimates of abundance. Unfortunately, obtaining unbiased estimates can be difficult due to inappropriate estimator models and study design. We evaluate population,density estimators for tigers Panthera tigris in Kanha Tiger Reserve, India, using camera traps in conjunction with telemetry (n=6) in a known minimum population of 14 tigers. An effort of 462 trap nights over 42 days yielded 44 photographs of 12 adult tigers. Using closed population estimators, the best-fit model (program capture) accounted for individual heterogeneity (Mh). The least biased and precise population estimate ( (SE) []) was obtained by the Mh Jackknife 1 (JK1) [14 (1.89)] in program care -2. Tiger density ( (SE) []) per 100 km2 was estimated at 13 (2.08) when the effective trapping area was estimated using the half mean maximum distance moved (1/2 MMDM), 8.1 (2.08), using the home-range radius, 7.8 (1.59), with the full MMDM and 8.0 (3.0) with the spatial likelihood method in program density 4.1. The actual density of collared tigers (3.27 per 100 km2) was closely estimated by home-range radius at 3.9 (0.76), full MMDM at 3.48 (0.81) and spatial likelihood at 3.78 (1.54), but overestimated by 1/2 MMDM at 6 (0.81) tigers per 100 km2. Sampling costs (Rs. 450 per camera day) increased linearly with camera density, while the precision of population estimates leveled off at 25 cameras per 100 km2. At simulated low tiger densities, a camera density of 50 per 100 km2 with an effort of 8 trap nights km,2 provided 95% confidence coverage, but estimates lacked precision. [source] Effects of trapping effort and trap shyness on estimates of tiger abundance from camera trap studiesANIMAL CONSERVATION, Issue 3 2004Per Wegge Camera trapping has recently been introduced as an unbiased and practical method for monitoring tiger abundance. In a high density area in the Royal Bardia National Park in lowland Nepal, we tested this method by trapping very intensively within a 25 km2 area to determine the true number of animals in that area. We then tested the effect of study design by sub-sampling the data set using varying distances between trap stations and by reducing the number of trapping nights at each station. We compared these numbers with the density estimates generated by the capture,recapture models of the program CAPTURE. Both distance between traps and trapping duration greatly influenced the results. For example, increasing the inter-trap distance from 1 to 2.1 km and reducing the trapping duration per station from 15 to 10 nights reduced the number of tigers captured by 25%. A significant decrease in trapping rates during successive 5-night periods suggested that our tigers became trap-shy, probably because of the photo flash and because they detected the camera traps from cues from impression pads 50 m from the traps. A significant behavioural response was also confirmed by the program CAPTURE. The best capture,recapture model selected by the computer program (Mbh) gave precise estimates from data collected by the initial 1 km spacing of traps. However, when we omitted data from half the number of traps, thus decreasing the sampling effort to a more realistic level for monitoring purposes, the program CAPTURE underestimated the true number of tigers. Most probably, this was due to a combination of trap shyness and the way the study was designed. Within larger protected areas, total count from intensive, stratified subsampling is suggested as a complementary technique to the capture,recapture method, since it circumvents the problem of trap shyness. [source] Vertebrate Fruit Removal and Ant Seed Dispersal in the Neotropical Ginger Renealmia alpinia (Zingiberaceae),BIOTROPICA, Issue 2 2009Carlos García-Robledo ABSTRACT Plants frequently display fruit characteristics that support multiple seed-dispersal syndromes. These ambiguous characteristics may reflect the fact that seed dispersal is usually a complex process involving multiple dispersers. This is the case for the Neotropical ginger Renealmia alpinia (Zingiberaceae). It was originally suggested that the aromatic fruits of R. alpinia located at the base of the plant are adapted for terrestrial mammal seed dispersal. However, the dark-purple coloration of the fruits and bright orange aril surrounding the seeds suggest that birds may play a role in R. alpinia seed dispersal. At La Selva Biological Station, Costa Rica, we used camera traps to record vertebrate visits to infructescences of R. alpinia. Most visitors were toucans and aracaris (Ramphastidae). However fruits were also removed by terrestrial mammals (coatis and armadillos). In addition to vertebrate fruit removal, some of the fruits dehisce and the seeds that fall on the ground are dispersed by ants. Fruitfall traps showed that 77 percent of fruits are removed by vertebrates. However, 15 percent of fruits fall to the base of parent plants to be potentially dispersed by ants. Experiments using a laboratory ant colony showed that ants are effective seed dispersers of R. alpinia. Ant seed manipulation increased germination success and reduced time to germination. In conclusion, primary seed dispersal in the Neotropical ginger R. alpinia is mostly performed by birds, additionally ants are effective dispersers at short distances. Seed dispersal in R. alpinia is a complex process involving a diverse array of dispersal agents. RESUMEN Los frutos de algunas plantas presentan características que se ajustan a más de un síndrome de dispersión. Es posible que estas características ambiguas reflejen el hecho de que la dispersión de semillas es usualmente un proceso complejo que involucra múltiples organismos dispersores. Ese es el caso de la Zingiberaceae Neotropical Renealmia alpinia. Originalmente se sugirió que los frutos aromáticos y la posición basal de las infrutescencias de R. alpinia son adaptaciones para la dispersión por mamíferos terrestres. Sin embargo, el color morado oscuro del exocarpo y el color anaranjado de los arilos en los frutos maduros sugieren que las aves pueden jugar un papel importante en la dispersión de semillas de R. alpinia. En la estación Biológica La Selva, Costa Rica, usamos cámaras trampa para registrar las visitas por invertebrados a las infrutescencias de R. alpinia. La mayoría de las visitas fueron por tucanes y arasaríes (Ramphastidae). La dispersión de semillas en R. alpinia puede ser aún más compleja pues parte de los frutos maduros liberan semillas en la base de la planta, las cuales son dispersadas por hormigas. Trampas de frutos registraron 77% de los frutos removidos por vertebrados. Sin embargo las semillas de 15% de los frutos cayeron en el suelo para ser potencialmente dispersadas por hormigas. Experimentos en laboratorio demostraron que las hormigas son dispersores efectivos de R. alpinia. Semillas manipuladas por hormigas germinaron en mayor proporción y presentaron una reducción en el tiempo de germinación. En conclusión, los frutos de R. alpinia son principalmente dispersados por aves. Adicionalmente, las hormigas son eficaces dispersoras de semillas a cortas distancias. La dispersión de semillas en R. alpinia es un proceso complejo que involucra un diverso gremio de agentes dispersores. [source] Brazilian Tapir Density in the Pantanal: A Comparison of Systematic Camera-Trapping and Line-Transect SurveysBIOTROPICA, Issue 2 2008Mogens Trolle ABSTRACT The density of Brazilian tapirs (Tapirus terrestris) was studied in the northeastern part of the Pantanal wetlands of Brazil using two simultaneous and independent methods: (1) systematic camera trapping combined with capture,recapture analysis, with camera traps spaced 1 km apart and distributed over 54 km2; and (2) line-transect sampling using an array of 12 linear transects, from 3.8 to 7.2 km long, covering the principal open and forest habitat types across the entire 1063 km2 SESC Pantanal Reserve. The two methods yielded conservative density estimates of 0.58 ± 0.11 tapirs/km2 (camera trapping) and 0.55 (95% CI 0.30,1.01) tapirs/km2 (line transects). The study suggests that certain Pantanal habitats and sites can sustain relatively high population densities of tapirs when these animals are protected from hunting. Further testing of the camera-trapping methodology as applied to tapirs is required, particularly focusing on extending the survey period. As it represents a relatively rapid method for estimating population density, in comparison to line-transect surveys, and as it generates information simultaneously on multiple species that are conservation priorities, we recommend that camera-trapping surveys be applied more widely across a variety of Pantanal habitats and land-use categories in order to confirm the value of the vast 140,000 km2 wilderness region for this vulnerable species. RESUMO A densidade de Tapirus terrestris foi avaliada na região Nordeste do Pantanal do Mato Grosso usando dois métodos simultâneos e independentes: 1) método sistemático com armadilhas fotográficas, combinado com análises de captura e recaptura, com câmaras fotográficas espaçadas 1 km entre si e distribuídas sobre uma área de 54 km2, dispostas em 4 grades contínuas, com 14 câmaras ativas por 9 dias consecutivos em cada grade; e 2) 12 transecções lineares variando em dimensões de 3,8,7,2 km de extensão, cobrindo os principais habitats abertos e fechados, sobre uma região de 1063 km2 da Reserva Particular do Patrimônio Natural SESC Pantanal. Os dois métodos resultaram em estimativas de densidade de 0.58 ± 0.11 antas/km2 (câmaras fotográficas) e 0.55 (95% intervalo de confiança 0.30,1.01) antas/km2 (transecções lineares). Os resultados sugerem que certos hábitats e áreas do Pantanal podem sustentar densidades relativamente elevadas de antas, quando protegidas da caça. A metodologia utilizando câmaras fotográficas em estudos sobre antas deve ser testada incrementando períodos de avaliação. Como o método representa uma forma rápida de avaliação das densidades populacionais, em comparação com transecções lineares, e gera informações simultâneas sobre múltiplas espécies que podem ser prioritárias para conservação, recomendamos que avaliações com armadilhas fotográficas sejam amplamente aplicadas para a espécie na variedade de hábitats do Pantanal, visando afirmar o valor dessa vasta e selvagem região de 140.000 km2. [source] | ||||||||||