Prey-switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarce
Abstract Background Optimal foraging theory explains how animals make foraging decisions based on the availability, nutritional content, and handling times of different food types. Generalists solve this problem by consuming a variety of food types, and alter their diets with relative ease. Speciali...
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| Format: | Article |
| Language: | English |
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BMC
2020-02-01
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| Series: | BMC Ecology |
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| Online Access: | http://link.springer.com/article/10.1186/s12898-020-00279-6 |
| _version_ | 1818692483585933312 |
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| author | Kristen Petrov Ricky-John Spencer Natasha Malkiewicz Jessica Lewis Claudia Keitel James U. Van Dyke |
| author_facet | Kristen Petrov Ricky-John Spencer Natasha Malkiewicz Jessica Lewis Claudia Keitel James U. Van Dyke |
| author_sort | Kristen Petrov |
| collection | DOAJ |
| description | Abstract Background Optimal foraging theory explains how animals make foraging decisions based on the availability, nutritional content, and handling times of different food types. Generalists solve this problem by consuming a variety of food types, and alter their diets with relative ease. Specialists eat few food types, and may starve if those food types are not available. We integrated stable isotope analyses with previously-published stomach contents and environmental data to investigate how the foraging ecologies of three sympatric freshwater turtle species vary across four wetlands that differ in turbidity and primary producer abundance. Results We found that the generalist Emydura macquarii consumes a varied diet (but mostly filamentous green algae) when primary producers are available and water is clear, but switches to a more carnivorous diet when the water is turbid and primary producers are scarce, following the predictions of optimal foraging theory. In contrast, two more-specialized carnivorous species, Chelodina expansa and Chelodina longicollis, do not differ in diet across wetlands, and interspecific competition may increase where E. macquarii is carnivorous. When forced to be more carnivorous, E. macquarii exhibits higher rates of empty stomachs, and female turtles have reduced body condition, but neither Chelodina species are affected. Conclusions Our results provide support for optimal foraging theory, but also show that the ability to change diet does not protect the generalist from experiencing lower foraging success when its preferred food is rare, with direct consequences for their energy budgets. Our results have conservation implications because wetlands in the Murray–Darling river system are increasingly turbid and have low macrophyte abundance, and all three species are declining. |
| first_indexed | 2024-12-17T12:58:31Z |
| format | Article |
| id | doaj.art-f443ce1e44b94ad29985a01ffae7d3a4 |
| institution | Directory Open Access Journal |
| issn | 1472-6785 |
| language | English |
| last_indexed | 2024-12-17T12:58:31Z |
| publishDate | 2020-02-01 |
| publisher | BMC |
| record_format | Article |
| series | BMC Ecology |
| spelling | doaj.art-f443ce1e44b94ad29985a01ffae7d3a42022-12-21T21:47:26ZengBMCBMC Ecology1472-67852020-02-0120111210.1186/s12898-020-00279-6Prey-switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarceKristen Petrov0Ricky-John Spencer1Natasha Malkiewicz2Jessica Lewis3Claudia Keitel4James U. Van Dyke5School of Science, Hawkesbury Institute, Western Sydney UniversitySchool of Science, Hawkesbury Institute, Western Sydney UniversitySchool of Science, Hawkesbury Institute, Western Sydney UniversitySchool of Science, Hawkesbury Institute, Western Sydney UniversitySchool of Life and Environmental Sciences, University of SydneySchool of Science, Hawkesbury Institute, Western Sydney UniversityAbstract Background Optimal foraging theory explains how animals make foraging decisions based on the availability, nutritional content, and handling times of different food types. Generalists solve this problem by consuming a variety of food types, and alter their diets with relative ease. Specialists eat few food types, and may starve if those food types are not available. We integrated stable isotope analyses with previously-published stomach contents and environmental data to investigate how the foraging ecologies of three sympatric freshwater turtle species vary across four wetlands that differ in turbidity and primary producer abundance. Results We found that the generalist Emydura macquarii consumes a varied diet (but mostly filamentous green algae) when primary producers are available and water is clear, but switches to a more carnivorous diet when the water is turbid and primary producers are scarce, following the predictions of optimal foraging theory. In contrast, two more-specialized carnivorous species, Chelodina expansa and Chelodina longicollis, do not differ in diet across wetlands, and interspecific competition may increase where E. macquarii is carnivorous. When forced to be more carnivorous, E. macquarii exhibits higher rates of empty stomachs, and female turtles have reduced body condition, but neither Chelodina species are affected. Conclusions Our results provide support for optimal foraging theory, but also show that the ability to change diet does not protect the generalist from experiencing lower foraging success when its preferred food is rare, with direct consequences for their energy budgets. Our results have conservation implications because wetlands in the Murray–Darling river system are increasingly turbid and have low macrophyte abundance, and all three species are declining.http://link.springer.com/article/10.1186/s12898-020-00279-6Optimal foragingBody conditionFood websEnvironmental changeStable isotopes |
| spellingShingle | Kristen Petrov Ricky-John Spencer Natasha Malkiewicz Jessica Lewis Claudia Keitel James U. Van Dyke Prey-switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarce BMC Ecology Optimal foraging Body condition Food webs Environmental change Stable isotopes |
| title | Prey-switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarce |
| title_full | Prey-switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarce |
| title_fullStr | Prey-switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarce |
| title_full_unstemmed | Prey-switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarce |
| title_short | Prey-switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarce |
| title_sort | prey switching does not protect a generalist turtle from bioenergetic consequences when its preferred food is scarce |
| topic | Optimal foraging Body condition Food webs Environmental change Stable isotopes |
| url | http://link.springer.com/article/10.1186/s12898-020-00279-6 |
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