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Experimental evidence that group size generates divergent benefits of cooperative breeding for male and female ostriches

Melgar, Julian LU ; Schou, Mads F. LU ; Bonato, Maud ; Brand, Zanell ; Engelbrecht, Anel ; Cloete, Schalk W. P. and Cornwallis, Charlie K. LU (2022) In eLife 11.
Abstract

Cooperative breeding allows the costs of parental care to be shared, but as groups become larger, such benefits often decline as competition increases and group cohesion breaks down. The counteracting forces of cooperation and competition are predicted to select for an optimal group size, but variation in groups is ubiquitous across cooperative breeding animals. Here, we experimentally test if group sizes vary because of sex differences in the costs and benefits of cooperative breeding in captive ostriches, Struthio camelus, and compare this to the distribution of group sizes in the wild. We established 96 groups with different numbers of males (1 or 3) and females (1, 3, 4, or 6) and manipulated opportunities for cooperation over... (More)

Cooperative breeding allows the costs of parental care to be shared, but as groups become larger, such benefits often decline as competition increases and group cohesion breaks down. The counteracting forces of cooperation and competition are predicted to select for an optimal group size, but variation in groups is ubiquitous across cooperative breeding animals. Here, we experimentally test if group sizes vary because of sex differences in the costs and benefits of cooperative breeding in captive ostriches, Struthio camelus, and compare this to the distribution of group sizes in the wild. We established 96 groups with different numbers of males (1 or 3) and females (1, 3, 4, or 6) and manipulated opportunities for cooperation over incubation. There was a clear optimal group size for males (one male with four or more females) that was explained by high costs of competition and negligible benefits of cooperation. Conversely, female reproductive success was maximised across a range of group sizes due to the benefits of cooperation with male and female group members. Reproductive success in intermediate sized groups was low for both males and females due to sexual conflict over the timing of mating and incubation. Our experiments show that sex differences in cooperation and competition can explain group size variation in cooperative breeders.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
eLife
volume
11
article number
e77170
publisher
eLife Sciences Publications
external identifiers
  • scopus:85139127580
  • pmid:36193678
ISSN
2050-084X
DOI
10.7554/eLife.77170
language
English
LU publication?
yes
id
d1afd8c9-0852-493e-ab2a-354ff31d5b4f
date added to LUP
2022-12-19 10:28:58
date last changed
2024-04-18 16:32:29
@article{d1afd8c9-0852-493e-ab2a-354ff31d5b4f,
  abstract     = {{<p>Cooperative breeding allows the costs of parental care to be shared, but as groups become larger, such benefits often decline as competition increases and group cohesion breaks down. The counteracting forces of cooperation and competition are predicted to select for an optimal group size, but variation in groups is ubiquitous across cooperative breeding animals. Here, we experimentally test if group sizes vary because of sex differences in the costs and benefits of cooperative breeding in captive ostriches, Struthio camelus, and compare this to the distribution of group sizes in the wild. We established 96 groups with different numbers of males (1 or 3) and females (1, 3, 4, or 6) and manipulated opportunities for cooperation over incubation. There was a clear optimal group size for males (one male with four or more females) that was explained by high costs of competition and negligible benefits of cooperation. Conversely, female reproductive success was maximised across a range of group sizes due to the benefits of cooperation with male and female group members. Reproductive success in intermediate sized groups was low for both males and females due to sexual conflict over the timing of mating and incubation. Our experiments show that sex differences in cooperation and competition can explain group size variation in cooperative breeders.</p>}},
  author       = {{Melgar, Julian and Schou, Mads F. and Bonato, Maud and Brand, Zanell and Engelbrecht, Anel and Cloete, Schalk W. P. and Cornwallis, Charlie K.}},
  issn         = {{2050-084X}},
  language     = {{eng}},
  publisher    = {{eLife Sciences Publications}},
  series       = {{eLife}},
  title        = {{Experimental evidence that group size generates divergent benefits of cooperative breeding for male and female ostriches}},
  url          = {{http://dx.doi.org/10.7554/eLife.77170}},
  doi          = {{10.7554/eLife.77170}},
  volume       = {{11}},
  year         = {{2022}},
}