[MARMAM] New publication: A new method to study inshore whale cue distribution from land-based observations (Patricia Arranz)
parranz at st-andrews.ac.uk
Sat Nov 16 15:03:39 PST 2013
We are pleased to announce our recent publication:
"A new method to study inshore whale cue distribution from land-based
Patricia Arranz, Sea Mammal Research Unit, University of St Andrews,
Scotland and Department of Animal Biology, La Laguna University, Spain.
David Borchers, Centre for Research into Environmental and
Ecological Modeling, University of St Andrews, Scotland.
Natacha Aguilar de Soto, Sea Mammal Research Unit, University of St
Andrews, Scotland and Department of Animal Biology, La Laguna
Mark P. Johnson, Sea Mammal Research Unit, University of St Andrews,
Martin J. Cox, Pelagic Ecology Research Group, Scottish Oceans
Institute, University of St Andrews, Scotland.
Author for correspondence: parranz at st-andrews.ac.uk
The challenges involved in the visual detection of some cetacean species
make it difficult to obtain information about their distribution and
habitat preferences using traditional sampling methods. This is
particularly the case for species such as beaked whales that spend a
small amount of time at the surface and have inconspicuous surface
behavior. The coastal waters around El Hierro (Canary Islands) hold
year-round populations of two beaked whale species, Cuvier's (/Ziphius
cavirostris/) and Blainville's (/Mesoplodon densirostris/), providing an
ideal scenario to set up land-based point transect surveys to study the
inshore behavior of these deep-diving species. This work extends
traditional distance sampling methods to allow the distribution of
animals seen from an observation point on the coast to be modeled with
respect to a nonlinear environmental feature (water depth). Depth is a
key factor delimiting marine habitats and is especially relevant for
understanding the distribution of deep-diving species such as beaked
whales, which approach the seafloor to feed. Our model predicts the
highest density of beaked whale cues around the 1,000 m isobath and most
(90%) of beaked whale groups surfacing in waters with seabed depths
between 325 and 1,660 m depth. The distribution of the sightings suggest
that the habitat selection of both species is probably driven by an
increased prey availability on the slope of the island. Because the
number of sightings at a given depth is not necessarily proportional to
the number of groups present, in this particular case additional
information on surfacing rates, and how they vary with depth, will be
required to draw inferences about animal distribution. We conclude that
this method is useful to investigate the distribution and habitat
selection of animals in relation to environmental variables using
observations from land and that future development work will allow
covariates in the detection function or multiple environmental features
to be considered when implementing density estimates.
The pdf can be downloaded from here:
Or a pdf copy can be obtained upon request to: _parranz at st-andrews.ac.uk
<mailto:parranz at st-andrews.ac.uk>_
Patricia Arranz, Ph. D.
Sea Mammal Research Unit
Scottish Oceans Institute
School of Biology
University of St Andrews
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