This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Some female animals living in groups raise offspring that are not their own, sometimes without reproducing themselves. While the behavior of cooperatively breeding species is well documented, some aspects remain poorly understood.
Researchers at the University of Konstanz and other institutions recently carried out a cross-species comparative analysis aimed at shedding light on how cooperatively breeding females interact with each other, specifically whether they compete over reproduction or share reproductive and offspring-care responsibilities. Their paper, published in Proceedings of the Royal Society B, is part of a broader project called Co-BreeD (Cooperative-Breeding Database). "The initial motivation for this study came from finding more and more comparative analyses that classified 'species' in a superficial way and without paying attention to important nuances in the social system of the species (including between-population differences)," Dr.
Yitzchak Ben Mocha, first author of the paper, told Phys.org. "Specifically, it bothered me that some studies argued that in cooperative breeding species all females in a group but one 'forgo' self-breeding to support the offspring of a single dominant female. These scholars were consequently wondering why female helpers invest 'altruistically' in other females' fitness." For example, some past comparative studies classified cooperatively breeding birds like Western bluebirds (Sialia mexicana) and superb fairywrens (Malurus cyaneus) as exhibiting extreme female reproductive skew and used these data to explain why subordinate females forgo self-reproduction to help the dominant female breed.
When Ben Mocha and his colleagues reviewed the available demographic data, however, they observed that almost all nests of these species had no female helpers at all. "So, by definition there cannot be female reproductive skew in these species, and there is also no female alloparental care," said Ben Mocha. "These facts make these species irrelevant for answering questions about female reproductive cooperation." After observing inconsistencies in earlier comparative studies of shared offspring care, Ben Mocha and his colleagues set out to conduct a more thorough review of existing data.
First, they examined observations reported in earlier studies of 73 cooperatively breeding bird and mammal species to assess whether previous claims about female alloparental care were supported. A central goal of the team's recent analysis was to better understand the behavior of cooperatively breeding females. Specifically, they wished to determine whether cohabiting sexually mature females cooperated (i.e., helped to raise each other's offspring) or whether one female monopolized breeding while the others acted as helpers.
"In most cases, allomothers were sexually immature females or there were only male helpers, so no female really forwent self-breeding," said Ben Mocha. "We found that when multiple sexually mature females lived in the same group, they more often co-bred and helped to raise each other's offspring, rather than only suppressed each other's breeding. Our study also had a methodological objective.
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