Geographical distribution

This study investigated a resident community of Atlantic spotted dolphins (Stenella frontalis) on Little Bahama Bank (LBB) in the Bahamas utilizing a noninvasive molecular approach. Genetic template material was collected and extracted from fecal material of S. frontalis. Fine-scale population structure was found within LBB according to mitochondrial DNA (mtDNA) and microsatellites (Fst = 0.25317, P < 0.0001 and Fst = 0.04491, P < 0.0001, respectively). Three main social clusters (North, Central, South/Roam) exist on LBB and all clusters were found to be genetically distinct according to microsatellite analyses. Mitochondrial haplotypes revealed North and South/Roam were not differentiated, but Central was different from both. When separated by sex, males were less genetically structured than females. Males showed no evidence of structure according to Ost or Rst.

Worldwide research of bottlenose dolphins (Tursiops truncatus) has led to varied definitions and terminology regarding ways to group dolphins for study and management. An understanding of the demographic history and population structure of bottlenose dolphins residing within the Indian River Lagoon Estuary System (IRLES), Florida, is needed to help define the IRLES dolphin population: ecotype, population, or community. Using mitochondrial DNA sequencing and microsatellite genotyping, this study detected: (1) genetic differentiation between estuarine and coastal individuals (FstmtDNA=0.414, Fstmsat=0.057; p<0.05; K=2), (2) genetic differentiation between the Indian River Lagoon (IRL) and Mosquito Lagoon (ML) (FstmtDNA=0.0201, Fstmsat=0.0234; p<0.09), and (3) minute undefined sub-structure within the IRLES (FstmtDNA=-0.00 -0.0379, Fstmsat=0.00 - vii 0.0445; p>0.1). Additionally, within ML this study detected non-mixing cohabitation of two potential ecotypes, estuarine and coastal. These findings raise many questions regarding how dolphins are presently categorized and managed which are critical to population assessments including abundance, vital rates, and health.

The Major Histocompatibility Complex (MHC) encodes proteins critical to the vertebrate immune response; therefore MHC diversity is an indicator of population health. I have (1) Isolated exon 2 of the class II gene DQA in Tursiops truncatus in the North Indian River Lagoon (IRL) (n=17), South IRL (n=29) and adjacent Atlantic waters (n=20), (2) assessed genetic variability between groups, (3) developed a method to genotype individuals, (4) typed 11 unique alleles in 66 individuals, (5) detected geographic patterns of diversity between estuarine and coastal individuals (FST=0.1255, p<0.05), (6) found evidence of positive selection centered in the binding pockets P1, P6 and P9 of the peptide binding region (w=2.08), (7) found that patterns of polymorphism did not closely match patterns of diversity in neutral markers, (8) performed a pilot study with Orcinus orca. The initial findings highlight the need for further comparative work and suggest that silent mutations are not neutral.

I examined summer home range use of Altantic spotted dolphins in the Bahamas from 1991-2004. Home ranges for 86 dolphins using the 95% Fixed Kernel Density (FKD) estimator averages 62.o km2+=22.96 km2 and ranged from 24.8 km2 to 148.4 km2. Older animals and males had the largest ranges. Home range size did not vary with female reproductive status. core areas were defined by the 50% FKD contour and averaged 10.32 km2 +=5.47 km2. Habitat use was different between reproductive states for females. Non-reproductively active (NRA) females used deeped habitat. Behavioral use of the home range varied spatially. The core area was an important foraging area for males and reproductively active females. NRA females foraged more outside their core area compared to the core area.

Demographic changes, through immigration/emigration (or death) can affect the social and community structure of a population. This study reports on the effects of demographic changes following 2 intense hurricanes on two sympatric delphinid species: Atlantic bottlenose dolphins, Tursiops truncatus, and Atlantic spotted dolphins Stenella frontalis. Thirty percent of the bottlenose population was lost after the hurricanes, with an influx of roughly the same number of immigrants. The stable community split into two cohesive units. Preferences in association in relation to reproductive status and sex remained. Immigrants assimilated well into the population, especially males. There is a conflict of interest between resident males and females in accepting immigrants and often females find more resistance than males. Long-term analysis of spotted dolphins revealed a community structure defined by long-term site fidelity, natal philopatry of both sexes and three social clusters.