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In situ measures of foraging success and prey encounter reveal marine habitat-dependent search strategies


Thums, M and Bradshaw, CJA and Hindell, MA, In situ measures of foraging success and prey encounter reveal marine habitat-dependent search strategies, Ecology, 92, (6) pp. 1258-1270. ISSN 0012-9658 (2011) [Refereed Article]

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Copyright 2011 Ecological Society of America

DOI: doi:10.1890/09-1299.1


Predators are thought to reduce travel speed and increase turning rate in areas where resources are relatively more abundant, a behavior termed "area-restricted search." However, evidence for this is rare, and few empirical data exist for large predators. Animals exhibiting foraging site fidelity could also be spatially aware of suitable feeding areas based on prior experience; changes in movement patterns might therefore arise from the anticipation of higher prey density. We tested the hypothesis that regions of area-restricted search were associated with a higher number of daily speed spikes (a proxy for potential prey encounter rate) and foraging success in southern elephant seals (Mirounga leonina), a species exhibiting both area-restricted searches and high interannual foraging site fidelity. We used onshore morphological measurements and diving data from archival tags deployed during winter foraging trips. Foraging success was inferred from in situ changes in relative lipid content derived from measured changes in buoyancy, and first-passage time analysis was used to identify area-restricted search behavior. Seals exhibited relatively direct southerly movement on average, with intensive search behavior predominantly located at the distal end of tracks. The probability of being in search mode was positively related to changes in relative lipid content; thus, intensively searched areas were associated with the highest foraging success. However, there was high foraging success during the outward transit even though seals moved through quickly without slowing down and increasing turning rate to exploit these areas. In addition, the probability of being in search mode was negatively related to the number of daily speed spikes. These results suggest that movement patterns represent a response to prior expectation of the location of predictable and profitable resources. Shelf habitat was 4–9 times more profitable than the other habitats, emphasizing the importance of the East Antarctic shelf for this and other predators in the region. We have provided rare empirical data with which to investigate the relationship between predator foraging strategy and prey encounter/ foraging success, underlining the importance of inferring the timing and spatial arrangement of successful food acquisition for interpreting foraging strategies correctly.

Item Details

Item Type:Refereed Article
Keywords:area-restricted search, first-passage time, foraging success, Macquarie Island, Australia, Mirounga leonina, movement patterns, predictability, profitability, southern elephant seal
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Environmental Management
Objective Group:Coastal and estuarine systems and management
Objective Field:Assessment and management of coastal and estuarine ecosystems
UTAS Author:Thums, M (Ms Michele Thums)
UTAS Author:Hindell, MA (Professor Mark Hindell)
ID Code:76846
Year Published:2011
Web of Science® Times Cited:72
Deposited By:IMAS Research and Education Centre
Deposited On:2012-03-14
Last Modified:2017-10-31

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