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Line-transect Surveys (line-transect + survey)

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Life Sciences100%

Selected Abstracts

Brazilian Tapir Density in the Pantanal: A Comparison of Systematic Camera-Trapping and Line-Transect Surveys

BIOTROPICA, Issue 2 2008
Mogens 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]

Design and field methods for sighting surveys of cetaceans in coastal and riverine habitats

MAMMAL REVIEW, Issue 1 2008
STEVE DAWSON
ABSTRACT 1Dolphins and porpoises in coastal and/or riverine habitats face serious conservation threats, yet surveys of their abundance are often especially difficult due to the challenges imposed by the habitats. Because many of these species occur in developing countries, lack of resources imposes a further set of challenges. 2We offer advice on designing and conducting line-transect surveys with a focus on sound, practical, design rather than analytical sophistication, and we attempt, where possible, to offer simple, inexpensive solutions. 3We guide the reader through the questions of what kind of survey should be done, whether by boat or aircraft, and we discuss ways to avoid bias and increase precision. 4Our treatment of field methods focuses especially on robust, but low-cost, approaches. We provide two case studies to illustrate the implementation of these ideas. [source]

Seasonal changes in distribution of Hector's dolphin at Banks Peninsula, New Zealand: implications for protected area design

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2010
William Rayment
Abstract 1.The efficacy of protected areas for wildlife management is largely dependent on appropriate design. It is therefore crucial that the distribution of target species is well understood. 2.The Banks Peninsula Marine Mammal Sanctuary (BPMMS) was designed to protect Hector's dolphins from bycatch in gillnets. However, the Banks Peninsula dolphin population is likely to be still declining, partly due to continued bycatch outside the boundaries of the BPMMS. 3.A three year series of aerial line-transect surveys around Banks Peninsula was carried out to investigate seasonal changes in distribution of Hector's dolphins out to 20 nautical miles (37,km) from the coast. 4.Dolphin sightings were concentrated close to shore in shallow water in summer, but were more evenly distributed throughout the study area in winter. A greater proportion of dolphins were sighted outside the 4 nautical miles (7.4,km) offshore boundary of the BPMMS in winter (mean=56%) than in summer (mean=19%) (G=88.25, df=1, P<0.001). 5.Partial Mantel tests revealed the effects of distance offshore and depth on dolphin occurrence while controlling for spatial autocorrelation and multicollinearity within the data. Distance offshore had the strongest and most consistent effect on dolphin presence, while depth had a strong effect in summer only. 6.It is proposed that restrictions on gillnetting around Banks Peninsula must be extended in order to reduce bycatch of Hector's dolphins to a sustainable level, and that a new offshore boundary of the BPMMS would be best defined by distance from the coast. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Brazilian Tapir Density in the Pantanal: A Comparison of Systematic Camera-Trapping and Line-Transect Surveys

BIOTROPICA, Issue 2 2008
Mogens 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]