Influences on dusky dolphin (<Emphasis Type="Italic">Lagenorhynchus obscurus</Emphasis>) fission-fusion dynamics in Admiralty Bay,New Zealand |
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Authors: | Heidi C Pearson |
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Institution: | (1) Department of Wildlife and Fisheries Sciences, Texas A&M University, 5007 Avenue U, Galveston, TX 77551, USA;(2) Present address: Whale Center of New England, 24 Harbor Loop, Gloucester, MA 01930, USA |
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Abstract: | In societies characterized by a high degree of fission-fusion dynamics, individuals adjust their grouping patterns according
to the shifting balance of costs and benefits associated with grouping. This study examines influences on fission-fusion dynamics
for dusky dolphins (Lagenorhynchus obscurus) in Admiralty Bay, New Zealand. This area is an important foraging habitat for dusky dolphins during the winter and spring.
Admiralty Bay has little predation risk, but nearshore mussel farms may infringe on available habitat. I used generalized
estimating equations to determine the influences of coordinated foraging, predation risk, and presence of mussel farms on
party size, rate of fission-fusion, and behavioral state. I conducted 168 boat-based group focal follows totaling 168 h. The
proportion of individuals observed foraging was positively related to party size and rate of party fusion. Resting had no
effect on party size and did not vary according to location. Near mussel farms, traveling decreased, and rate of party fission
decreased. I conclude that (1) coordinated foraging strategies are a primary influence on fission-fusion dynamics within this
population, (2) dolphins may respond to decreased predation risk by not adjusting party size or location during resting, and
(3) areas near mussel farms are not used for traveling. |
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Keywords: | Dusky dolphin Lagenorhynchus obscurus New Zealand Fission-fusion Behavior |
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