There are many fig wasp species in which armored wingless males battle to the death to gain access to females inside of figs. Using their jaws to inflict lethal injuries, they will at times tear off the heads of their rivals. However, up until now, it was uncertain who was fighting whom as the males are of the same species and so seemingly related.
Generally speaking, it goes against kin selection for males to murder their brothers. Since they carry similar genetics and the reproductive successes of one offers indirect genetic benefits for the other, siblicide in nature is quite rare. It can often be avoided as well if brothers don’t occur in the same figs. But it can happen if mate competition is especially intense or in cases where brothers just don’t recognize one another. There are even instances of course where different but closely related wasp species which are occupying the same fig could wage war.
According to James Cook of the University of Readings report to the New Scientist, “We do find severed heads quite often.” His team was the first to conduct a genetic analysis of fighting fig wasps before testing alternative fighting scenarios for three Sycoscapter wasp species in Ficus rubiginosa fig fruits.
Finding that approximately 80% of fights occurred between males from the same species with a surprising 20% between males of different species was unexpected due to the simple fact that only males of the same species are actual rivals for females. The team believes that it’s a real possibility that the wasps don’t recognize their opponents or perhaps even prefer to strike first. In this case, it can be difficult to properly gauge your enemy within a crowded, dark fruit whilst measuring them up. After all, they may have already killed you by then, Cook told New Scientist.
Also finding that few figs contained brothers, this meant that females were more likely laying just one son per fig. Their work was later published in Ecological Entomology. Though fighting to the death isn’t typical behavior in the animal kingdom even between elephants or stags, these wasps might only live for a couple of days once matured and non-pollinating species may never even emerge from the fig. “Although they’re risking their life, the future value of their life is actually quite small,” Cook says. Given just three females or so to successfully mate with inside each fig, each chance could be the last.