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A Rapid UAV Method for Assessing Body Condition in Fur Seals

1
School of Life and Environmental Sciences, Deakin University, Warrnambool, VIC 3280, Australia
2
CSIRO Health and Biosecurity, Townsville, QLD 4811, Australia
3
School of Life and Environmental Sciences, Deakin University, Burwood, VIC 3125, Australia
*
Author to whom correspondence should be addressed.
Drones 2019, 3(1), 24; https://doi.org/10.3390/drones3010024
Received: 18 February 2019 / Revised: 5 March 2019 / Accepted: 5 March 2019 / Published: 6 March 2019
(This article belongs to the Special Issue Drones for Coastal Environments)
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Abstract

Condition indices correlating body lipid content with mass and morphometric measurements have been developed for a variety of taxa. However, for many large species, the capture and handling of enough animals to obtain representative population estimates is not logistically feasible. The relatively low cost and reduced disturbance effects of UAVs make them ideal for the rapid acquisition of high volume data for monitoring large species. This study examined the imagery collected from two different UAVs, flown at 25 m altitude, and the subsequent georeferenced orthomosaics as a method for measuring length and axillary girth of Australian fur seals (Arctocephalus pusillus doriferus) to derive an index of body condition. Up to 26% of individuals were orientated correctly (prostrate/sternal recumbent) to allow for body measurements. The UAV-obtained images over-estimated axillary girth diameter due to postural sag on the lateral sides of the thorax while the animals are lying flat in the sternal recumbent position on granite rocks. However, the relationship between axillary girth and standard length was similarly positive for the remotely- and physically-obtained measurements. This indicates that residual values from the remotely-obtained measurements can be used as a relative index of body condition. View Full-Text
Keywords: body condition; axillary girth; Australian fur seals (Arctocephalus pusillus doriferus) body condition; axillary girth; Australian fur seals (Arctocephalus pusillus doriferus)
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Allan, B.M.; Ierodiaconou, D.; Hoskins, A.J.; Arnould, J.P. A Rapid UAV Method for Assessing Body Condition in Fur Seals. Drones 2019, 3, 24.

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