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Edited by Joan E. Strassmann, Washington University in St. Louis, St. Louis, MO, and approved September 23, 2015 (received for review June 26, 2015)
Significance
Parents in many animal species care for their offspring. In some species, males care more; in other species, females care more; in still other species, the contribution of the sexes is equal. However, we do not know what explains these differences among species. Using the most comprehensive analyses of parental care to date, here we show that parents cooperate more when sexual selection is not intense and the adult sex ratio of males to females is not strongly skewed. However, the degree of parental cooperation is unrelated to harshness and predictability of the ambient environment during the breeding season. Our work therefore suggests that several types of parental care may coexist in a given set of ambient environment.
Abstract
Parental care is one of the most variable social behaviors and it is an excellent model system to understand cooperation between unrelated individuals. Three major hypotheses have been proposed to explain the extent of parental cooperation: sexual selection, social environment, and environmental harshness. Using the most comprehensive dataset on parental care that includes 659 bird species from 113 families covering both uniparental and biparental taxa, we show that the degree of parental cooperation is associated with both sexual selection and social environment. Consistent with recent theoretical models parental cooperation decreases with the intensity of sexual selection and with skewed adult sex ratios. These effects are additive and robust to the influence of life-history variables. However, parental cooperation is unrelated to environmental factors (measured at the scale of whole species ranges) as indicated by a lack of consistent relationship with ambient temperature, rainfall or their fluctuations within and between years. These results highlight the significance of social effects for parental cooperation and suggest that several parental strategies may coexist in a given set of ambient environment.
Footnotes
- ↵1To whom correspondence should be addressed. Email: vladimir.remes{at}upol.cz.
Author contributions: V.R., R.P.F., A.L., and T.S. designed research; V.R. performed research; V.R., R.P.F., and J.T. contributed new reagents/analytic tools; V.R. analyzed data; and V.R., R.P.F., J.T., A.L., and T.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The data reported in this paper have been deposited in the Dryad Digital Repository, dx.doi.org/10.5061/dryad.02jk0.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1512599112/-/DCSupplemental.
Parental cooperation in birds
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