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MEPS 682:1-12 (2022)  -  DOI:

Luck and tactics in foraging success: the case of the imperial shag

Rory P. Wilson1,*, Mark D. Holton2, Andrew Neate3,4, Monserrat Del’Caño5, Flavio Quintana5, Ken Yoda6, Agustina Gómez-Laich7

1Biosciences, College of Science, Swansea University, Singleton Campus, Swansea SA2 8PP, UK
2Department of Computer Science, College of Science, Swansea University Bay Campus, Fabian Way, Swansea SA1 8EN, UK
3Department of Mathematics, College of Science, Swansea University Bay Campus, Fabian Way, Swansea SA1 8EN, UK
4School of Mathematics and Statistics, Faculty of Science, Technology, Engineering and Mathematics, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
5Instituto de Biología de Organismos Marinos (IBIOMAR), CONICET, Boulevard Brown 2915, Puerto Madryn U9120ACD, Chubut, Argentina
6Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku 464-8601, Nagoya, Japan
7Departamento de Ecología, Genética y Evolución & Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA), CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II Ciudad Universitaria C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina
*Corresponding author:

ABSTRACT: It has been proposed that predators searching for prey acquire food according to a probabilistic framework, where success is based on ‘luck’ and the odds of success vary with prey abundance. If true, this has major ramifications for variation in the rates of energy acquisition within animal populations, which is particularly pertinent in offspring provisioning and breeding success, because smaller animals (the young) cannot starve for as long as the adults. However, despite much general speculation about rates of food acquisition, no study has measured whether food encounter is probabilistic in wild animals. We used animal-mounted cameras to document all prey captures by wild imperial shags Leucocarbo atriceps as they hunted underwater and show that, although they mostly do not have inter-prey acquisition time distributions that accord with a ‘luck-based’ framework assuming a constant probability of finding prey over time, there is no difference in the predicted amount of food captured between models that use the empirical data or theoretical Poisson-based fits of the data. We also noted considerable inter-individual differences in foraging success that far exceeded any differences between empirical and theoretical inter-prey acquisition time distributions. The data were used in a probabilistic foraging model that made explicit the mechanistic link between random prey encounters and food-dependent breeding success, indicating that ‘less lucky’ individuals could not provision their broods at rates commensurate with normal growth while the ‘lucky’ birds could do so easily. Given the nature of food encounter in these birds, coupled with substantial inter-individual variation in foraging success, we suggest that more successful individuals are particularly choosey about when, how and where to forage, which results in them operating with higher odds of success.

KEY WORDS: Leucocarbo atriceps · Cormorant · Foraging ecology · Gambling · Probability of food encounter · Tactics

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Cite this article as: Wilson RP, Holton MD, Neate A, Del’Caño M, Quintana F, Yoda K, Gómez-Laich A (2022) Luck and tactics in foraging success: the case of the imperial shag. Mar Ecol Prog Ser 682:1-12.

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