Dear all,
We are pleased to share with you our publication entitled: "from
high-resolution to low-resolution dive datasets: a new index to quantify the
foraging effort of marine predators." K. Heerah, M. Hindell, C. Guinet and J-B
Charrassin, Animal Biotelemetry 2015
(http://www.animalbiotelemetry.com/content/3/1/42)
This methodological paper presents a different approach to identifiy and
calculate foraging effort in low-resolution dive profiles that are transmitted
by satellite. We therefore believe this could be useful to the community as the
method can be applied to different species. Please do not hesitate to contact
us if you have any questions regarding the application of the method to your
own dataset.
Abstract:Background. In the last decade thousands of Satellite Relayed data
Loggers (SRDLs) have been deployed, providing large datasets on marine predator
movement patterns at sea and their diving behaviour. However, the latter is in
a highly summarised, low resolution form, from which it is difficult to make
the sorts of important behavioural inferences that are possible from higher
resolution data sets (such as detection of likely foraging events). The main
objective of this study was to develop a simple but accurate tool to detect and
quantify within-dive foraging periods in low resolution dives. Method. Two
southern elephant seals were fitted with a head mounted Time Depth Recorder
(TDR) (recording depth at 1 Hz) and an accelerometer (recording 3 axes of
acceleration at 16 Hz) from which prey capture attempts were estimated (PrCA),
and a Weddell seal was also fitted with a TDR (1 Hz).The resulting
high-resolution dive profiles were used to: (i) calculate an accurate index of
foraging effort based on the detection of vertical sinuosity switches (i.e.
huntinghighres time), (ii) produce a SRDL equivalent low-resolution dataset
using a broken stick algorithm; and (iii) from each low-resolution dive
calculate a set of candidate foraging effort indices. Results. Huntinglowres
time, which is the total time spent in decreased vertical velocity segments of
the dive, was the foraging effort index that best correlated with
huntinghighres time. Huntinghighres mode of SES dives (highly sinuous parts of
high-resolution dives) was associated with 77% of total PrCA. In comparison,
Huntinglowres segments of SES dives were associated with 68% of PrCA as well as
with four times more PrCA than transitlowres segments. Conclusion. We found a
low-resolution index which indicates foraging activity within a highly
summarised dive profile and which identified most PrCA, despite degraded
information transmitted by SLDRs. Used in combination with other measurements
of the in situ environment, the huntinglowres index could be used in numerous
integrated marine ecology studies, such as habitat use studies that are crucial
to facilitate more effective conservation.
All the best,
Karine Heerah------------------
PhD in Marine ecologyUPMC - IMAS
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