DIGITAL PHOTOGRAPHY IMPROVES EFFICIENCY OF INDIVIDUAL DOLPHIN IDENTIFICATION

Methods for reliably identifying and monitoring individuals are critically important to understanding the behavior of animals. Naturally occurring distinctive features have proven particularly useful for studies of free-ranging populations of marine mammals, especially in those cases where artificial marking could potentially harm animals or bias behavioral data collected (Wells et al. 1999). Since its first use in the 1970s (e.g., Wiirsig and Wursig 1977, Katona et al. 1979, Shane 1980, Payne et al. 1983), photo-identification has emerged as a dependable, noninvasive technique for measuring social grouping, movements, residency, abundance, and life history of many cetacean species (summarized in Mann 2000). It has proven particularly useful for examining associations between individuals at different spatial and temporal scales (Whitehead 1997). Most photo-identification studies of dolphins and porpoises rely on nicks and cuts in the dorsal fin that provide long-lasting, individually unique markings (Wursig and Jefferson 1990); some body scars and pigmentation patterns also persist over many years and can be used for identification (Lockyet and Morris 1990). Many techniques have been developed to standardize and facilitate comparison of photographic records including tracing of dorsal fins onto standardized sheets and calculation of parameters such as the dorsal ratio (Deftan et al. 1990, Kreho et al. 1999). With the advent of computer-aided photo-identification database sorting (Whitehead 1990) and semiautomated photographic matching techniques (Hiby and Love11 1990, Araabi et al. ZOOO), catalogs of distinctively marked individuals are increasingly being maintained in a digitized format. These methods considerably decrease analysis time for large photographic catalogs (Araabi et al.