Published April 13, 2021
1School of Life and Environmental Sciences, Deakin University, Burwood, VIC, Australia
2CSIRO Health and Biosecurity, Townsville, Queensland, Australia
3Department of Ecology & Evolutionary Biology, University of California, Santa Cruz, CA, United States of America
4Department of Ecology & Evolutionary Biology, University of California, Santa Cruz, United States of America
5Universidad San Francisco de Quito and Galapagos Science Center, Islas Galápagos, Ecuador
6Dirección Parque Nacional Galápagos, Oficina Técnica Operativa San Cristóbal, Islas Galápagos, Ecuador
The endangered Galapagos sea lion (GSL, Zalophus wollebaeki) exhibits a range of foraging strategies utilising various dive types including benthic, epipelagic and mesopelagic dives. In the present study, potential prey captures (PPC), prey energy consumption and energy expenditure in lactating adult female GSLs (n = 9) were examined to determine their foraging efficiency relative to the foraging strategy used.
Individuals displayed four dive types: (a) epipelagic (<100 m; EP); or (b) mesopelagic (>100 m; MP) with a characteristic V-shape or U-shape diving profile; and (c) shallow benthic (<100 m; SB) or (d) deep benthic (>100 m; DB) with square or flat-bottom dive profiles. These dive types varied in the number of PPC, assumed prey types, and the energy expended. Prey items and their energetic value were assumed from previous GSL diet studies in combination with common habitat and depth ranges of the prey.
In comparison to pelagic dives occurring at similar depths, when diving benthically, GSLs had both higher prey energy consumption and foraging energy expenditure whereas PPC rate was lower. Foraging efficiency varied across dive types, with benthic dives being more profitable than pelagic dives.
Three foraging trip strategies were identified and varied relative to prey energy consumed, energy expended, and dive behaviour. Foraging efficiency did not significantly vary among the foraging trip strategies suggesting that, while individuals may diverge into different foraging habitats, they are optimal within them. These findings indicate that these three strategies will have different sensitivities to habitat-specific fluctuations due to environmental change.
Blakeway J, Arnould JPY, Hoskins AJ, Martin-Cabrera P, Sutton GJ, Huckstadt LA, Costa DP, Páez-Rosas D, Villegas-Amtmann S. 2021. Influence of hunting strategy on foraging efficiency in Galapagos sea lions. PeerJ 9:e11206 https://doi.org/10.7717/peerj.11206
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