Colleagues,
The following paper was recently published in a special issue of a
journal that does not typically print marine mammal articles (sad as
that may be). I thought some of you may be interested. The article
is freely available for download at http://aslo.org/lo/toc/vol_53/
issue_5_part_2 or by request to me.
Kind regards,
Mark Baumgartner
Baumgartner, M.F. and D.M. Fratantoni. 2008. Diel periodicity in
both sei whale vocalization rates and the vertical migration of their
copepod prey observed from ocean gliders. Limnology and Oceanography
53: 2197-2209.
Abstract:
The daily activity cycles of marine predators may be dictated in
large part by the timing of prey availability. For example, recent
studies have observed diel periodicity in baleen whale vocalization
rates that are thought to be governed by the diel vertical migration
of their zooplanktonic prey. We addressed this hypothesis by studying
associations between sei whale (Balaenoptera borealis) vocalization
rates, oceanographic conditions, and the vertical distribution of the
whales’ prey, the calanoid copepod Calanus finmarchicus, during May
2005 in the southwestern Gulf of Maine using an array of autonomous
ocean gliders. Each of the four gliders was equipped with sensors to
measure temperature, salinity, and chlorophyll fluorescence. Three of
the four gliders carried a digital acoustic recorder and the fourth
carried a 1-MHz acoustic Doppler current profiler. We observed strong
diel periodicity in the acoustic backscatter measured by the current
profiler that we attribute (based on a corroborating shipboard study)
to the diel vertical migration of C. finmarchicus. Sei whale
vocalization rates also exhibited diel periodicity, with more calls
detected during the daytime when C. finmarchicus was observed at
depth. We found no evidence to suggest that the observed patterns in
sei whale calling rates were attributable to diel periodicity in
background noise or acoustic propagation conditions. Sei whales are
adept at foraging on nearsurface aggregations of C. finmarchicus;
therefore we expect that the whales were feeding at night. We
hypothesize that calling rates are reduced at night while the whales
are feeding, but increase with social activity during the day when
copepods are either more difficult or less efficient to capture at
depth. The gliders’ persistence during adverse weather conditions
experienced during the study allowed continuous collocated
observations of whale vocalization behavior and oceanographic
conditions that have not been previously possible with traditional
shipboard techniques.
Mark Baumgartner
Assistant Scientist
Biology Department
Woods Hole Oceanographic Institution
MS #33, Redfield 256
Woods Hole, MA 02543
[EMAIL PROTECTED]
http://www.whoi.edu/sites/mbaumgartner
(508)289-2678 phone
(508)457-2134 fax
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