Popular male dolphins produce more offspring
Date:
March 24, 2022
Source:
University of Zurich
Summary:
The reproductive success of male dolphins is not determined by
strength or age, but via social bonds with other males. The better
integrated males are in their social network, the more offspring
they produce, a new study has shown using long-term behavioral
and genetic data.
FULL STORY ==========================================================================
The reproductive success of male dolphins is not determined by strength
or age, but via social bonds with other males. The better integrated
males are in their social network, the more offspring they produce, a
new study by an international team of researchers led by the University
of Zurich has shown using long-term behavioral and genetic data.
==========================================================================
Male dolphins in Shark Bay, Western Australia live in complex social
groups in which they form long-lasting bonds to cooperate with other
males. To do this, they join in large, stable alliances. Within these alliances, males form smaller, less stable groups of two to three to mate
with females, steal them from other alliances or defend against attacks.
Cooperating for the purpose of reproduction "This kind of male
cooperation for the purpose of reproduction is highly unusual in the
animal kingdom. It's only been observed in a much less complex form
in some other primates," says Livia Gerber, a former PhD student at
the Department of Anthropology of the University of Zurich. Together
with an international team led by UZH professor Michael Kru"tzen, she
wanted to find out whether the dolphins' complex social life affects
the reproductive success of males, or whether, as in most other species, stronger or more experienced males are more likely to sire offspring. The researchers analyzed 30 years of behavioral data from 85 male dolphins
and used genetic data to conduct paternity analyses for more than 400
dolphins.
Social bonds more important than strength and age The study showed that well-integrated "popular" males with strong social bonds to many alliance partners produce the most offspring. Partner stability within the smaller, variable groups of two to three males and the age difference to alliance members, in contrast, played no role in the animals' reproductive success.
Previous research had suggested that social bonds improve the animals'
chances of survival, increase their longevity and lead to better immune responses and health. While all these effects might contribute to a male dolphin's lifetime reproductive success, the positive effect of social
bond strength on cooperation was probably the key factor, according to
first author Gerber: "Well-integrated males might be in a better position
to harness the benefits of cooperation and access crucial resources such
as food or mates. They may also be more resilient to partner loss compared
to those with few, but closer partners." Long-lasting friendships improve fitness Cooperation among social partners is very common in mammals,
but its influence on paternity success has not yet been studied in
depth. However, understanding the factors that determine reproductive
success and thus individual fitness is at the core of evolutionary
biology. "Our study is the first to show that social bonds among male
dolphins positively impact their reproductive success and are, therefore, directly linked to fitness," says senior author Michael Kru"tzen. "This
had previously only been observed in male chimpanzees and some other
primates. Our study expands upon previous findings on land mammals and
provides compelling evidence that such highly complex, multi-level social systems also developed independently in the ocean."
========================================================================== Story Source: Materials provided by University_of_Zurich. Note: Content
may be edited for style and length.
========================================================================== Journal Reference:
1. Livia Gerber et al. Social integration influences fitness in
allied male
dolphins. Current Biology, 24 March 2022 DOI:
10.1016/j.cub.2022.03.027 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220324122506.htm
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