Individual variation in functional response parameters is explained by body size but not by behavioural types in a poeciliid fish
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Functional responses are per-capita feeding rate models whose parameters often scale with individual body size but the parameters may also be further influenced by behavioural traits consistently differing among individuals, i.e. behavioural types or animal personalities. Behavioural types may intrinsically lead to lower feeding rates when consistently shy, inactive and easily stressed individuals cannot identify or respond to risk-free environments or need less food due to lower metabolic rates linked to behaviour. To test how much variation in functional response parameters is explained by body size and how much by behavioural types, we estimated attack rate and handling time individually for differently sized female least killifish (Heterandria formosa) and repeatedly measured behavioural traits for each individual. We found that individual fish varied substantially in their attack rate and in their handling time. Behavioural traits were stable over time and varied consistently among individuals along two distinct personality axes. The individual variation in functional responses was explained solely by body size, and contrary to our expectations, not additionally by the existing behavioural types in exploration activity and coping style. While behavioural trait-dependent functional responses may offer a route to the understanding of the food web level consequences of behavioural types, our study is so far only the second one on this topic. Importantly, our results indicate in contrast to that previous study that behavioural types do not per se affect individual functional responses assessed in the absence of external biotic stressors.
KeywordsAllometric relationships Food webs Foraging Trait variation Population structure
We are grateful to the members of the B-Types group at IGB for discussions. Special thanks goes to Kate Laskowski, David Bierbach and Pep Alós for help with repeatability score calculations, video analysis in EthoVision, and multivariate regression analysis, respectively. We also like to thank two anonymous reviewers for their helpful comments.
Author contribution statement
AS and GK designed the experiment, AS performed the feeding trials and behavioural assays, GK analysed the videos, AS analysed the data and wrote the manuscript, GK and RA commented on statistical analysis and manuscript.
Compliance with ethical standards
AS was supported by an IGB Postdoc Fellowship and a Marie Sklodowska Curie Fellowship (Horizon-2020-IEF, Grant # 660643). GK and RA were supported via the B-Types project through the Leibniz Competition Pact for Innovation and Research (SAW-2013-IGB-2). GK also acknowledges funding from the German Science Foundation DFG (KA-3029/2-1).
All applicable institutional and/or national guidelines for the care and use of animals were followed.
Conflict of interest
The authors declare that they have no conflict of interests.
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