The sex of and genetic relatedness among interacting individuals are known to be
biologically fundamental features that characterize the composition of animal groups.
Current work continues to illuminate reasons for the variety of animal social patterns,
including patterns in group membership. I investigated the composition of dusky
dolphin groups relative to sex and relatedness at two locations in New Zealand. In
Kaikoura, dusky dolphins are found year-round, foraging nocturnally on verticallymigrating
prey and socializing in distinct group types (mating, nursery, and adult) during
the day. By contrast, dusky dolphins use Admiralty Bay, where they feed diurnally on
small schooling fishes, primarily in the winter. Molecular sexing revealed the sex of 107
dusky dolphins. The Kaikoura data support previous findings that small mating groups
consist mostly of males and indicate that small adult groups can consist of either or both
sexes. In Admiralty Bay, the percentage of female dolphins present during the study
was estimated to be only 7.4%âÂÂ22.2% (95% confidence interval, n=88). A
randomization test further indicates that dusky dolphins in Admiralty Bay grouped
preferentially with same-sex individuals. Nuclear and mitochondrial markers were used
to investigate patterns of relatedness. Dusky dolphins sampled in Kaikoura (n=17) and
Admiralty Bay (n=47) were genotyped at seven microsatellite loci, and genetic
relatedness among all genotyped pairs was estimated. A randomization test indicates
that dusky dolphins did not group preferentially by relatedness in Admiralty Bay.
Grouping history for 13 genotyped samples was also known from a multi-year
photographic record of individually distinctive dusky dolphins. No relationship was found between these longer-term grouping patterns and genetic relatedness. The d-loop
region of the mitochondrial DNA (mtDNA) was sequenced for 197 dusky dolphins. The
pattern of grouping among dolphins with different haplotypes indicates that dusky
dolphin groups are not strongly structured by maternal lineages. However, data from
eight individual dusky dolphins hint that nursery groups in Kaikoura tend to consist of
dolphins that share a maternal ancestor. This investigation raises many questions about
the nature of dusky dolphin social organization and suggests promising avenues for
finer-grained investigations into the causes and consequences of dusky dolphin group
structure.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4970 |
| Date | 25 April 2007 |
| Creators | Shelton, Deborah Ellen |
| Contributors | Würsig, Bernd |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 467855 bytes, electronic, application/pdf, born digital |
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