Toxin constraint explains diet choice, survival and population dynamics in a molluscivore shorebird

Recent insights suggest that predators should include (mildly) toxic prey when non-toxic food is scarce. However, the assumption that toxic prey is energetically as profitable as non-toxic prey misses the possibility that non-toxic prey have other ways to avoid being eaten, such as the formation of...

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Bibliographic Details
Published in:Proceedings of the Royal Society B: Biological Sciences
Main Authors: van Gils, Jan A., van der Geest, Matthijs, Leyrer, Jutta, Oudman, Thomas, Lok, Tamar, Onrust, Jeroen, de Fouw, Jimmy, van der Heide, Tjisse, van den Hout, Piet J., Spaans, Bernard, Dekinga, Anne, Brugge, Maarten, Piersma, Theunis
Format: Article in Journal/Newspaper
Language:English
Published: 2013
Subjects:
diet choice
hydrogen sulphide
optimal foraging theory
predator-prey interactions
survival rate
toxins
KNOTS CALIDRIS-CANUTUS
AFFECTS FORAGING DECISIONS
RED KNOTS
BANC-DARGUIN
STRATEGIC DECISIONS
EDUCATED PREDATORS
CHEMICAL DEFENSE
APOSEMATIC PREY
WARNING SIGNALS
MARKED ANIMALS
Calidris canutus
Red Knot
Online Access:https://hdl.handle.net/11370/11c7b4d1-7384-42c7-a8ce-59a2ec3656ee
https://research.rug.nl/en/publications/11c7b4d1-7384-42c7-a8ce-59a2ec3656ee
https://doi.org/10.1098/rspb.2013.0861
https://pure.rug.nl/ws/files/6796675/2013ProcRSocBvGilsSupp.pdf
https://pure.rug.nl/ws/files/6796676/2013ProcRSocBvGils.pdf
Description
Summary:Recent insights suggest that predators should include (mildly) toxic prey when non-toxic food is scarce. However, the assumption that toxic prey is energetically as profitable as non-toxic prey misses the possibility that non-toxic prey have other ways to avoid being eaten, such as the formation of an indigestible armature. In that case, predators face a trade-off between avoiding toxins and minimizing indigestible ballast intake. Here, we report on the trophic interactions between a shorebird (red knot, Calidris canutus canutus) and its two main bivalve prey, one being mildly toxic but easily digestible, and the other being non-toxic but harder to digest. A novel toxin-based optimal diet model is developed and tested against an existing one that ignores toxin constraints on the basis of data on prey abundance, diet choice, local survival and numbers of red knots at Banc d'Arguin (Mauritania) over 8 years. Observed diet and annual survival rates closely fit the predictions of the toxin-based model, with survival and population size being highest in years when the non-toxic prey is abundant. In the 6 of 8 years when the non-toxic prey is not abundant enough to satisfy the energy requirements, red knots must rely on the toxic alternative.

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