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

WILSON, RP; HOLTON, MD; NEATE, A; DEL CAÑO, MONSERRAT; QUINTANA, F; YODA, K; GÓMEZ-LAICH, A

MARINE ECOLOGY PROGRESS SERIES

INTER-RESEARCH

Año: 2022 vol. 682 p. 1 - 12

0171-8630

It has been proposed that predatorssearching for prey acquire food according to aprobabilistic framework, where success is based on?luck? and the odds of success vary with prey abundance.If true, this has major ramifications for variationin the rates of energy acquisition within animalpopulations, which is particularly pertinent inoffspring provisioning and breeding success, be -cause smaller animals (the young) cannot starve foras long as the adults. However, despite much generalspeculation about rates of food acquisition, nostudy has measured whether food encounter isprobabilistic in wild animals. We used animalmountedcameras to document all prey captures bywild imperial shags Leucocarbo atriceps as theyhunted underwater and show that, although theymostly do not have inter-prey acquisition time distributionsthat accord with a ?luck-based? frameworkassuming a constant probability of findingprey over time, there is no difference in the predictedamount of food captured between modelsthat use the empirical data or theoretical Poissonbasedfits of the data. We also noted considerableinter-individual differences in foraging success thatfar exceeded any differences between empiricaland theoretical inter-prey acquisition time distributions.The data were used in a probabilisticfor aging model that made explicit the mechanisticlink between random prey encounters and fooddependentbreeding success, indicating that ?lesslucky? individuals could not provision their broodsat rates commensurate with normal growth whilethe ?lucky? birds could do so easily. Given thenature of food encounter in these birds, coupledwith substantial inter-individual variation in foragingsuccess, we suggest that more successful individualsare particularly choosey about when, how and where to forage, which results in them operatingwith higher odds of success.