[MARMAM] New paper on harbour porpoise sleep

Andrew Wright marinebrit at gmail.com
Thu Oct 26 10:22:30 PDT 2017


Dear Marmam,

We are pleased to announce that our new paper on sleeping at depth in wild
harbour porpoise is now in press with Animal Behaviour. It is available
from myself (marinebrit at gmail.com), or online at:
https://www.sciencedirect.com/science/article/pii/S0003347217303020.

Highlights, abstract and keywords follow below.

Best,

Andrew
--
Andrew Wright, Ph.D.

VaquitaAreBrowncoats: Where Sci-Fi meets Science, the Cosmos meets
Conservation and Firefly meets Flipper. Shiny
https://www.facebook.com/vaquitaarebrowncoats.



Andrew J. Wright, Tomonari Akamatsu, Kim N. Mouritsen, Signe Sveegaard,
Rune Dietz, Jonas Teilmann. 2017. Silent porpoise: potential sleeping
behaviour identified in wild harbour porpoises. Animal Behaviour. Volume
133, November 2017, Pages 211–222.
https://doi.org/10.1016/j.anbehav.2017.09.015

Highlights
• Cetaceans only sleep with half of their brain at a time: unihemispherical
sleep.
• Behavioural sleep criteria were applied to data from tagged wild harbour
porpoise.
• Stereotyped parabolic-shaped dives found with low bioacoustic and
physical activity.
• Matching all possible criteria, parabolic dives are proposed to represent
sleeping.
• Quiet sleeping periods have implications for conservation and acoustic
methodology.

Abstract
All animals sleep and it is essential for maintaining optimal brain
function. However, cetaceans engage in the unusual practice of
unihemispherical sleep, where only half of their brain sleeps at a time,
due to their constant need for movement and breathing. Most studies of
sleep in cetaceans have occurred in captivity. However, tagging devices
have now developed to the point where the data collected from wild animals
can be assessed against published criteria for defining sleep
behaviourally. Seven acoustic and behavioural data loggers were deployed on
harbour porpoises, Phocoena phocoena, in Danish waters between May 2010 and
August 2011 and stayed on the animals between 53 and 72 h, recording 1884
to 2755 valid dives per animal. Parabolic dives with significantly reduced
bioacoustic activity and a stereotyped behavioural pattern were identified
as potential sleeping periods. The recordings for nearly half of the
parabolic dives were found to contain no vocalization (echolocation
clicks), significantly more than other dive types. Of the remaining
parabolic dives, the click rate was, when normalized to their individual
means, also significantly lower than detected in other dive types.
Additionally, parabolic dives were shallow compared to all other dive
types, and found to have a stereotypic low-energy profile. They were also
found to contain fewer rolls and incorporate a lower vertical descent rate
than most other dive types. If the data are representative, harbour
porpoises spend a small, but meaningful amount of their diving time engaged
in parabolic dives and thus potentially sleeping. All animals have a
fundamental need for undisturbed sleep. These quiet periods thus need to be
considered in studies of anthropogenic effects, but also those employing
passive acoustic monitoring techniques, as well as in efforts to reduce
incidental bycatch in fisheries, given the associated periods of reduced
environmental awareness.

Keywords
A-tag; acoustic tags; data storage tags; echolocation; harbour porpoise;
Phocoena; satellite telemetry; sleeping behaviour
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