Estimating the abundance of cetaceans (whales and dolphins) from survey data is particularly challenging because animals are only intermittently available for detection and animal densities are typically low. This is true whether surveys are conducted above water (sighting animals on the surface) or below water (acoustic surveys, for example).
Standard distance sampling methods cope well with low densities but do not cope well with intermittent animal availability. More versatile methods of inference are obtained by combining distance sampling and mark-recapture methods. The combined methods are able to cope with some, but not all kinds of intermittent animal availability. We obtain a richer set of methods if we consider detection to be analogous to death, and apply some ideas from survival analysis in a distance sampling context.
After a brief overview of distance sampling and related mark-recapture methods, I will describe some new and existing methods that integrate ideas from distance sampling, mark-recapture and survival analysis, illustrate them using cetacean survey data, and review their advantages over existing methods as well as their limitations.
Keywords: Cetaceans; Distance sampling; Mark-recapture; Survival analysis
Biography: David Borchers is an applied statistician at the University of St Andrews with a background in the development and application of statistical methods for assessing wildlife populations. His research interests include distance sampling and mark-recapture survey methods. After graduating from the University of Cape Town he spent some years working for the International Whaling Commission, estimating whale abundance in the Antarctic, before moving into academia.