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One day, Seizi Suzuki and his colleagues Nagano and Kobayashi decided to study the variation in aggression between the sexes of carrion beetles and explore whether or not this indicates that these beetles exhibit resource defense polygyny.
It was previously found that male-male aggression occurred but not female-female aggression over a carcass. Suzuki wanted to know if this indicated that the carrion beetles exhibit resource defense polygyny. So, they took this to the test and collected four virgin carrion beetles differing in all sizes. This included two female and two male.
Haha! I have more offspring than you!
Then, they put the four beetles in an area with a piece of meat. The larger carrion beetles were dominant over the smaller males and won fights. The larger males also defended the resource.
Great job, colleagues!
While this was happening, the females crawled around. They were caught mating with both males and laid eggs on the meat. After several weeks, then the larvae started to crawl away from the meat. The researches used DNA fingerprinting to find out who the offspring's parents were.
The DNA fingerprinting indicated that the large and small females had roughly the same reproductive success. The larger males sired three times more offspring than the small males.
In conclusion, it was found that carrion beetles exhibit a resource defense polygyny mating system. The larger dominant males defend the carcasses and females do not show aggression and share access to carcasses. While the dominant males defend the carcass, they mate with multiple females and have most of the offspring, which is an example of the polygyny threshold model.