Examining Stock Structure of Common Bottlenose Dolphins (Tursiops Truncatus) through Photo-Identification and Genetic Analyses

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Griffin, Emily Kathryn
Cox, Tara M.
Department of Marine Sciences
Common bottlenose dolphin
Home range
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Cetaceans range over large distances resulting in complex patterns of population structure. The coastal ecotype of common bottlenose dolphins (Tursiops truncatus) often consists of distinct groups that exhibit localized adaptations on small spatial scales that result in fine scale genetic structuring. Sex-specific home range patterns are common in cetacean species and may differ between geographic locations. The purpose of this study was to couple long-term photo-identification data with genetics to examine stock structure and to measure home range size of male and female common bottlenose dolphins in the estuarine waters around Savannah, GA. The study area was categorized into three segments: a) a north region, b) a buffer region, and c) a south region. Remote biopsy sampling was conducted in September 2015 and February and March 2017. No significant difference was found when regions were compared by sample location only (n=69). After animals without ≥10 sightings (n=45) were excluded from analysis, a significant difference in FST was found between the north versus buffer (p=0.0147). When the animals with ≥10 sightings were placed in the location with 50% or more of their sightings, a significant difference in in FST was found between the north versus buffer and north versus south (p=0.0018 and p=0.0164). With the addition of sighting history data, stronger subdivision was found between populations. No significant difference was found in minimum convex polygon home range size of males (105.34 ± 49.28 km2; n=24) and females (109.83 ± 53.29 km2; n=57) or in kernel density home range size. The addition of supplemental data, such as photo-identification, to a genetic analysis, can provide additional insight into stock structure. Methods used in this study could be employed by future studies to improve understanding of the complex stock structure of common bottlenose dolphins in estuarine waters.