Longer guts and higher food quality increase energy intake in migratory swans

van Gils, Jan A., Beekman, Jan H., Coehoorn, Pieter, Corporaal, Els, Dekkers, Ten, Klaassen, Marcel, van Kraaij, Rik, de Leeuw, Rinze and de Vries, Peter P. 2008, Longer guts and higher food quality increase energy intake in migratory swans, Journal of animal ecology, vol. 77, no. 6, pp. 1234-1241, doi: 10.1111/j.1365-2656.2008.01452.x.

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Title Longer guts and higher food quality increase energy intake in migratory swans
Author(s) van Gils, Jan A.
Beekman, Jan H.
Coehoorn, Pieter
Corporaal, Els
Dekkers, Ten
Klaassen, MarcelORCID iD for Klaassen, Marcel orcid.org/0000-0003-3907-9599
van Kraaij, Rik
de Leeuw, Rinze
de Vries, Peter P.
Journal name Journal of animal ecology
Volume number 77
Issue number 6
Start page 1234
End page 1241
Total pages 8
Publisher Wiley
Place of publication Oxford, England
Publication date 2008-11
ISSN 1365-2656
Keyword(s) digestive constraint
food quality
intake rate
phenotypic flexibility
Summary 1.  Within the broad field of optimal foraging, it is increasingly acknowledged that animals often face digestive constraints rather than constraints on rates of food collection. This therefore calls for a formalization of how animals could optimize food absorption rates.

2.  Here we generate predictions from a simple graphical optimal digestion model for foragers that aim to maximize their (true) metabolizable food intake over total time (i.e. including nonforaging bouts) under a digestive constraint.

3.  The model predicts that such foragers should maintain a constant food retention time, even if gut length or food quality changes. For phenotypically flexible foragers, which are able to change the size of their digestive machinery, this means that an increase in gut length should go hand in hand with an increase in gross intake rate. It also means that better quality food should be digested more efficiently.

4.  These latter two predictions are tested in a large avian long-distance migrant, the Bewick's swan (Cygnus columbianus bewickii), feeding on grasslands in its Dutch wintering quarters.

5.  Throughout winter, free-ranging Bewick's swans, growing a longer gut and experiencing improved food quality, increased their gross intake rate (i.e. bite rate) and showed a higher digestive efficiency. These responses were in accordance with the model and suggest maintenance of a constant food retention time.

6.  These changes doubled the birds’ absorption rate. Had only food quality changed (and not gut length), then absorption rate would have increased by only 67%; absorption rate would have increased by only 17% had only gut length changed (and not food quality).

7.  The prediction that gross intake rate should go up with gut length parallels the mechanism included in some proximate models of foraging that feeding motivation scales inversely to gut fullness. We plea for a tighter integration between ultimate and proximate foraging models.
Language eng
DOI 10.1111/j.1365-2656.2008.01452.x
Field of Research 060203 Ecological Physiology
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2008, The Authors
Persistent URL http://hdl.handle.net/10536/DRO/DU:30035080

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