Is bigger better?

Submitted by editor on 22 April 2020.Get the paper!

POPULAR SUMMARY: "The intensity of sexual selection, body size and reproductive success in a mating system with male–male combat: is bigger better?" (Glaudas et al. 2020)

We used radio-telemetry and DNA paternity analyses in a free-ranging population of South African puff adders (Bitis arietans) to investigate if larger males have a reproductive advantage compared to smaller ones, in this system where males are known to engage in ritual combats for female access. Radio-telemetry allowed us to: 1) keep track of the interactions between our radio-equipped males and females in the field; and 2) catch and bring the pregnant females back to the laboratory where they gave birth, allowing us to collect DNA samples on the offspring for paternity analyses. In contrast to what would be expected in a species where the males fight for females, that is, larger males have an advantage because they can defeat smaller ones, our results showed that male body size was not a key trait affecting reproduction. Both males and females mated multiply during a single mating season, and males—but not females—increased the number of offspring produced by mating with several partners. However, mating with additional females did not increase the number of offspring fathered by males that much, because multiple paternity, where a female’s litter is sired by more than one male, was very common. Females seemingly did not benefit from mating with different males, and we propose an evolutionary scenario explaining the tendency for female puff adders to mate with several males within a single mating season.


Video description: We set up a remote video-camera on one of our radio-equipped female puff adders (Bitis arietans) in ambush-foraging posture. One of our radio-equipped males finds her. The female reacted to the arrival of the male by puffing up, the typical defensive behavior of puff adders, and quickly left the scene, and the male seemingly followed her. Note that video speed differs by section.


Written by: Xavier Glaudas

Photo by: Xavier Glaudas


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