Diving deep in a foraging hotspot: acoustic insights into bottlenose dolphin dive depths and feeding behaviour |
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Authors: | GD Hastie B Wilson PM Thompson |
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Institution: | (1) University of Aberdeen, School of Biological Sciences, Lighthouse Field Station, Cromarty, Ross-Shire, UK;(2) Dunstaffnage Marine Laboratory, The Scottish Association for Marine Science, Argyll, Oban, PA37 1QA, UK;(3) Marine Mammal Research Unit, AERL, University of British Columbia, Vancouver, BC, Canada |
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Abstract: | To exploit resources in their environment, odontocete cetaceans have evolved sophisticated diving abilities to allow effective
foraging. However, data on the diving behaviour and underwater foraging behaviour remains limited. This study made use of
echolocation clicks and other calls to study the diving behaviour of bottlenose dolphins. Dolphins used the full water column
and consistently dived to depths of around 50 m, close to the seabed. However, the majority of their time appeared to be spent
within the surface layers of the water column. In addition, by localising calls that have been associated with prey capture
events (Janik, Proc R Soc Lond Ser B 267:923–927, 2000a), it appeared that certain forms of feeding behaviour occurred primarily
at depths of between 20 and 30 m. Furthermore, data on the depth of clicks made before and after these feeding calls suggested
that during the minute before the calls, dolphins were consistently diving from the surface to depths close to the seabed,
and were subsequently returning to the surface after the calls. This passive acoustic technique proved an accurate method
for studying the depth distribution of dolphin vocalisations. By exploiting the natural sounds made by these wild odontocetes,
this investigation provided a previously unavailable perspective on the the 3D nature of bottlenose dolphins foraging behaviour.
It confirmed that while the dolphins spent the majority of time close to the surface, the full water column was exploited
during foraging events. |
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