An analysis of reciprocal exchange of helping behavior in the red-cockaded woodpecker (Picoides borealis) |
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Authors: | M Z Khan J R Walters |
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Institution: | (1) Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0406, USA, US;(2) Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA e-mail: mkhan@princeton.edu Tel.: +1-609-2582543, Fax: +1-609-2582712, US |
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Abstract: | We examine the frequency of reciprocal exchanges of helping behavior in three red-cockaded woodpecker populations to determine
if such exchanges might constitute a significant fitness benefit of helping. Specifically, we determine how often helpers,
once they become breeders, are assisted by young they previously helped raise. The estimated frequencies of reciprocal exchange
of helping based on survival and status transition probabilities are low (2%). Observed frequencies of reciprocity are significantly
higher than estimated frequencies in two of the three populations studied, suggesting that male fledglings more often remain
on their natal territory as helpers if another helper is already present. High rates of retention of young males as helpers
on high-quality territories or preferential helping of kin, as well as preferential helping of former care-givers, might explain
this result. When the analysis is restricted to helpers unrelated to the young they help raise, which controls for preferential
helping of kin and largely eliminates effects of territory quality, empirical estimates of the frequency of reciprocity do
not differ from estimates calculated from population demography. We conclude that young males do not preferentially help former
care-givers and that reciprocal exchange of help is not an important factor in the evolution of helping behavior in the red-cockaded
woodpecker. In this species, all known benefits of helping behavior are indirect (i.e., derived through kin selection ) rather
than direct. We discuss the occurrence of unrelated helpers in this context.
Received: 10 August 1999 / Received in revised form: 13 February 2000 / Accepted: 19 February 2000 |
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Keywords: | Red-cockaded woodpecker Picoides borealis Reciprocity Helping behavior |
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