Offspring growth, survival and reproductive success in the bank vole: a litter size manipulation experiment |
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Authors: | Esa Koskela |
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Institution: | Department of Biological and Environmental Science, University of Jyv?skyl?, P.O. Box 35, FIN-40351 Jyv?skyl?, Finland Fax: +358-14-602321; e-mail: emk@tukki.jyu.fi, FI
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Abstract: | To estimate the optimality of brood size, it is essential to study the effects of brood size manipulation on offspring survival
and reproductive success. Moreover, testing the generality of the hypothesis of reproductive costs requires experimental data
from a diversity of organisms. Here I present data on the growth, survival and reproductive success of bank vole Clethrionomys glareolus individuals from manipulated litters. Furthermore, the survival of mothers whose litter size was manipulated was studied.
At weaning, the mean weight of pups from enlarged litters was lower and from reduced litters higher compared to control litters.
After winter, at the start of the breeding season, individuals from enlarged litters, especially males, were still lighter
than individuals from the other two treatments. Litter enlargements did not increase the number of reproducing female offspring
per mother, nor did the litter sizes of female offspring differ between treatments. There were no differences between treatments
in winter survival of offspring after weaning, but among female offspring, weaning weight explained the survival probabilities
over winter. A higher weight of females at winter determined the probability of starting to reproduce in spring. The survival
of mothers did not seem to be influenced by litter manipulation performed the previous year. According to the results, mothers
nursing enlarged or reduced litters do not gain any fitness benefits in terms of number of offspring surviving to breeding.
The results are consistent with the majority of experiments conducted in birds, which have found costs of enlarged brood appearing
as offspring trade-offs rather than parent trade-offs.
Received: 14 December 1997 / Accepted: 1 March 1998 |
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Keywords: | Life history trade-offs Mammals Reproductive success Reproductive costs Survival |
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