Dusky dolphins in New Zealand: group structure by sex and relatedness

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Title: Dusky dolphins in New Zealand: group structure by sex and relatedness
Author: Shelton, Deborah Ellen
Abstract: 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 % ? ? ? ? ? ?22 .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 .
URI: http : / /hdl .handle .net /1969 .1 /4970
Date: 2007-04-25


Dusky dolphins in New Zealand: group structure by sex and relatedness. Available electronically from http : / /hdl .handle .net /1969 .1 /4970 .

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