[MARMAM] Two new papers on sperm whales

Valeria Teloni vteloni at tiscali.it
Fri Mar 14 08:52:55 PDT 2008


Dear All,

For those who might be interested, the following two papers were
recently published:

Teloni, V., Zimmer, W. M. X., Wahlberg, M., and Madsen, P. T. (2007).
Consistent acoustic size estimation of sperm whales using clicks
recorded from unknown aspects. Journal of Cetacean Research and
Management 9: 127-136.

Abstract: The multipulse structure of sperm whale clicks offers a unique
way to acoustically estimate body length, as the inter-pulse intervals
within the clicks relate to the two-way travel time within and thereby
to the size of the hypertrophied nose in this species. Despite its large
potential to allow the estimation of length acoustically, the technique
has only been used in a few studies to assess the length composition of
sperm whale populations. Its limited use may relate to the fact that
only some clicks within a click series normally display the regular
multipulsed structure required for size estimation. The inter-pulse
intervals of usual clicks vary with the recording aspect to the clicking
whale and the pulse delays are not necessarily directly related to the
length of the spermaceti organ. To overcome these difficulties, a method
is provided to estimate sperm whale body lengths, based on averages of
cepstra derived from a large number of clicks recorded from whales in
unknown recording aspects. This study shows that the two-way travel time
in the spermaceti organ can consistently be estimated by a peak in the
averaged cepstra when a large number of clicks are analysed. This method
is shown to give a consistent estimation of the size of the spermaceti
organ when recording the whale in an unknown orientation and also when
recordings are heavily influenced by surface reflections.

Teloni, V., Johnson, M., Miller, P.O., and Madsen, P. T. (2008). Shallow
food for deep divers: dynamic foraging behavior of male sperm whales in
a high latitude habitat. Journal of Experimental Marine Biology and
Ecology 354: 119-131.

Abstract: Groups of female and immature sperm whales live at low
latitudes and show a stereotypical diving and foraging behavior with
dives lasting about 45 min to depths of between 400 and 1200 m. In
comparison, physically mature male sperm whales migrate to high
latitudes where little is known about their foraging behavior and
ecology. Here we use acoustic recording tags to study the diving and
acoustic behavior of male sperm whales foraging off northern Norway.
Sixty-five hours of tag data provide detailed information about the
movements and sound repertoire of four male sperm whales performing 83
dives lasting between 6 and
60 min. Dives ranged in depth between 14 and 1860 m, with a median depth
of 175 m, and 92% of the surfacings lasted less than
15 min. The four whales clicked for an average 91% (SD=10) of the dive
duration, where the first usual click was produced at depths ranging
between 4 and 218 m and the last usual click at depths ranging between 1
and 1114 m. Echolocation buzzes, which are used as an indication of prey
capture attempts, were emitted at depths between 17 and 1860 m, during
both the descent and ascent phase of deep dives. The foraging behavior
varied markedly with depth, with the timing and duration of prey capture
attempts during shallow dives suggesting that the whales target more
sparsely distributed prey. In contrast, deep dives involve frequent prey
capture attempts and seem to target more dense food layers. The evidence
of exploitation of different food layers, including epipelagic prey, is
consistent with the hypothesis that male sperm whales may migrate to
high latitudes to access a productive, multi-layered foraging habitat.

Copies are available upon request from: vteloni at tiscali.it

Best regards, Valeria
---
Valeria Teloni
+31 (0)6 17105152
vteloni at tiscali.it








More information about the MARMAM mailing list