PRIMES (PRogram for Interdisciplinary Mathematics, Ecology, and Statistics) is designed to address the challenges of studying complex ecological systems. Modern studies of ecological systems incorporate an extremely wide range of scientific and quantitative techniques, from the collection of data in the field, to the modeling of complex systems, to the application of advanced computational techniques. Consequently, quantitative ecology has become an inherently multi-disciplinary activity. Read More

Thursday, May 4, 2006

Multiple covariate and spatial distance sampling of African Savanna mammals

Reliable estimation of animal abundance is central to their effective management and conservation and scientific research. Distance sampling is a reliable method for estimating abundance when sightability of animals is of concern. Sightability may vary by distance to animals, habitat type, season, timing of survey, animal species, counting platform and observers. Recent extensions of distance sampling theory to multiple covariate and spatial distance sampling offer new opportunities for more efficient estimation of animal abundance and mapping of animal distributions.

We used multiple covariate and spatial distance sampling to estimate the abundances and map the distributions of a variety of African savanna mammals in order to test the efficiency and effectiveness of these methods and assess practical challenges to their successful application. Surveys were conducted during the wet and dry seasons, during daytime and nighttime as well as early and late in the daytime and nighttime. Angles were measured using Garmin Etrex Vista GPS, distances using Leitz laser range finder, and navigation along transects conducted using a Dell Axim pocket PC running ARCPAD software and attached to a Garmin GPS. This allowed us to assess the importance to the detection probabilities and hence efficiency of estimates of abundance for different species of season, timing of survey, observers, counting platform, habitat characteristics and multiple species associations. Finally we assessed the effectiveness of these surveys in terms of costs and time and offer practical suggestions on how to improve the conduct of multiple covariate and distance sampling surveys.