Timing of avian reproduction in unpredictable environments |
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Authors: | Jácint T?k?lyi John M McNamara Alasdair I Houston Zoltán Barta |
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Institution: | (1) Department of Evolutionary Zoology, University of Debrecen, Egyetem t?r 1, 4032 Debrecen, Hungary;(2) School of Mathematics, University of Bristol, University Walk, Bristol, BS8 1TW, UK;(3) School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, UK |
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Abstract: | Organisms living in periodically varying environments adjust their life history events to the changes in food availability.
When these changes are not entirely predictable animals face a trade-off between maintaining physiological preparedness (which
can be costly) and being unprepared (which decreases the chances of successful reproduction). To investigate this problem,
we developed an optimal annual routine model of gonad regulation in birds. Most birds regress their reproductive organs during
non-breeding periods, but to start breeding again they need to have functional gonads. Maintaining the gonads in this state
is costly, but because it takes time to achieve this state, if gonads are not functional the bird may miss a possible breeding
opportunity. We explore the resolution of this trade-off in environments where favorable periods can occur at any time of
the year and variability in the length of good and bad periods can be altered. Consistent with empirical studies of reproductive
behavior in unpredictable environments, we find that birds maintain the gonads partially activated during unfavorable conditions
in many cases. However, gonad regulation may differ strikingly depending on the consistency of the good and bad periods. Furthermore,
seasonal changes in food availability lead to the entrainment of reproduction and the segregation of the breeding and non-breeding
season, even if the magnitude of seasonality is small compared to the degree of environmental fluctuations. These results
indicate that several aspects of the environment need to be taken into account to understand reproductive behavior in unpredictable
environments. Given that the trade-off between the costs and benefits of maintaining physiological preparedness is not limited
to birds, our results have implications for understanding behavioral flexibility in other organisms as well. |
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