Abstract
This study investigated prey captures in free-ranging adult female Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted 3-axis accelerometers and animal-borne video cameras. Acceleration data was used to identify individual attempted prey captures (APC), and video data were used to independently verify APC and prey types. Results demonstrated that head-mounted accelerometers could detect individual APC but were unable to distinguish among prey types (fish, cephalopod, stingray) or between successful captures and unsuccessful capture attempts. Mean detection rate (true positive rate) on individual animals in the testing subset ranged from 67-100%, and mean detection on the testing subset averaged across 4 animals ranged from 82-97%. Mean False positive (FP) rate ranged from 15-67% individually in the testing subset, and 26-59% averaged across 4 animals. Surge and sway had significantly greater detection rates, but also conversely greater FP rates compared to heave. Video data also indicated that some head movements recorded by the accelerometers were unrelated to APC and that a peak in acceleration variance did not always equate to an individual prey item. The results of the present study indicate that head-mounted accelerometers provide a complementary tool for investigating foraging behaviour in pinnipeds, but that detection and FP correction factors need to be applied for reliable field application.
Highlights
Foraging success is one of the main determinants of individual survival (e.g. [1])
The present study examined the efficacy of head-mounted accelerometers to accurately detect attempted prey captures (APC) and identify prey type in free-ranging Australian fur seals (Arctocephalus pusillus doriferus) using animal-borne video data loggers to provide visual validation of prey capture success/misses and prey species identification
The current study focused LME analysis of the testing subset on 4 specific questions that could be directly applied to predicting prey capture success and prey type with accelerometers on free-ranging animals
Summary
Foraging success is one of the main determinants of individual survival (e.g. [1]). Factors that influence foraging success can impact reproductive success, population growth, and the survival of a species, as documented in both marine mammals [1,2,3,4,5] and diving birds [6,7,8]. Direct observation of foraging behaviour is not possible for most marine mammals and, alternate methods using animal-borne data loggers have attempted to provide this type of information. Dive characteristics obtained from time-depth-recorders (TDR) have been used over the last two decades to obtain information on diving behaviour as an indirect measure of foraging success There is uncertainty as to whether data from TDRs alone can differentiate between successful foraging, searching dives, unsuccessful attempted prey captures, or prey quantity or species [5,10,11,12,13,14]. Stomach sensor dataloggers can be used to complement inferred foraging from dive depth profiles, these dataloggers are not able to quantify feeding events or distinguish prey type [16,17,19]
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