Synergistic effects of predation and parasites on the overwinter survival of root voles
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Predators and parasites have been important extrinsic factors influencing the fluctuation of small mammal populations. They can have non-additive effects on a shared group of preys or hosts, which can have important consequences for population dynamics. However, experimental studies incorporating the interactions between predation and parasites are scarce in small mammal populations. Here we systematically examined the synergistic effects of predators and coccidian parasites interaction on overwinter survival and likely mechanisms underlying the synergistic effects in the root vole (Microtus oeconomus). Our aim was to test the general hypothesis that predators and coccidia interact synergistically to decrease overwinter survival of root voles through mediating vole’s physiological traits and body conditions. We carried out a factorial experimental design, by which we manipulated the predator exclusion in combination with the parasitic removal in enclosures, and then measured fecal corticosterone metabolite (FCM) levels, immunocompetence, and body conditions in captured animals via repeated live trapping. We found a strong negative synergistic effect of predators and coccidia on survival. Importantly, we found that predators increased both the prevalence and intensity of coccidian infection in voles through immune suppression induced by predation stress, while increased coccidian infection reduced plasma protein and hematocrit level of voles, which may impair anti-predator ability of voles and lead to an increase in predation. Our finding showed when voles are exposed to both predation risk and infection, their synergistic effects greatly reduce overwinter survival and population density. This may be an important mechanism influencing population dynamics in small mammals.
KeywordsPredation Parasite Stress Immunocompetence Overwinter survival
This work was Funded by the National Key Research and Development Program of China (Grant/Award Number: 2016YFC0501901), Strategic Priority Research Program of Chinese Academy of Sciences (Grant/Award Number: XDA2005010406) and the National Natural Science Foundation of China (Grant No., 31570421). We thank Yan-Bin Yang for his assistance in the field work and biochemical assays.
Author contribution statement
JHB and YW conceived and designed the experiments. GZS, YHZ, YFC performed the experiments. JHB and GZS analyzed the data. GZS wrote the manuscript. JHB and YW provided editorial advice.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Human and animal rights statement
The use of animals in this study was in accordance with the guidelines of the regulations of experiments on animals and was approved by the animal Ethics and Welfare committee of the Northwest Institute of Plateau Biology, Chinese Academy of Science.
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