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From video recordings to whisker stable isotopes: a critical evaluation of timescale in assessing individual foraging specialisation in Australian fur seals

Citation

Kernaleguen, L and Dorville, N and Ierodiaconou, D and Hoskins, AJ and Baylis, AMM and Hindell, MA and Semmens, J and Abernathy, K and Marshall, GJ and Cherel, Y and Arnould, JPY, From video recordings to whisker stable isotopes: a critical evaluation of timescale in assessing individual foraging specialisation in Australian fur seals, Oecologia, 180, (3) pp. 657-670. ISSN 0029-8549 (2016) [Refereed Article]

Copyright Statement

Copyright 2015 Springer-Verlag

DOI: doi:10.1007/s00442-015-3407-2

Abstract

Estimating the degree of individual specialisation is likely to be sensitive to the methods used, as they record individuals' resource use over different time-periods. We combined animal-borne video cameras, GPS/TDR loggers and stable isotope values of plasma, red cells and sub-sampled whiskers to investigate individual foraging specialisation in female Australian fur seals (Arctocephalus pusillus doriferus) over various timescales. Combining these methods enabled us to (1) provide quantitative information on individuals' diet, allowing the identification of prey, (2) infer the temporal consistency of individual specialisation, and (3) assess how different methods and timescales affect our estimation of the degree of specialisation. Short-term inter-individual variation in diet was observed in the video data (mean pairwise overlap = 0.60), with the sampled population being composed of both generalist and specialist individuals (nested network). However, the brevity of the temporal window is likely to artificially increase the level of specialisation by not recording the entire diet of seals. Indeed, the correlation in isotopic values was tighter between the red cells and whiskers (mid- to long-term foraging ecology) than between plasma and red cells (short- to mid-term) (R 2 = 0.93-0.73 vs. 0.55-0.41). δ13C and δ15N values of whiskers confirmed the temporal consistency of individual specialisation. Variation in isotopic niche was consistent across seasons and years, indicating long-term habitat (WIC/TNW = 0.28) and dietary (WIC/TNW = 0.39) specialisation. The results also highlight time-averaging issues (under-estimation of the degree of specialisation) when calculating individual specialisation indices over long time-periods, so that no single timescale may provide a complete and accurate picture, emphasising the benefits of using complementary methods.

Item Details

Item Type:Refereed Article
Keywords:Arctocephalus pusillus, diet, nested network, time aggregating, vibrissae
Research Division:Agricultural and Veterinary Sciences
Research Group:Fisheries Sciences
Research Field:Aquatic Ecosystem Studies and Stock Assessment
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Marine Environments
Author:Hindell, MA (Professor Mark Hindell)
Author:Semmens, J (Associate Professor Jayson Semmens)
ID Code:102474
Year Published:2016
Funding Support:Australian Research Council (DP110102065)
Web of Science® Times Cited:14
Deposited By:Centre for Ecology and Biodiversity
Deposited On:2015-08-24
Last Modified:2017-11-08
Downloads:0

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