You've heard people say they'll do anything for love, but new research shows that one species of bird takes this motto to an extreme. Males of the lekking bird species Otis tarda may eat poisonous beetles to look healthier and become more attractive to females during mating season, according to the study.
The study was published on October 22 in the open-access journal PLOS One.
Both sexes of lekking birds consume blister beetles during mating season. This beetle contains a chemical called cantharidin which is toxic to the bird, but has an anti-parasitic effect which can make the bird look healthier. This compound can also prevent sexually transmitted diseases in the birds. Although both male and female lekking birds consume this beetle, the male birds eat more of them than the females, and male birds choose them consistently even when other insects are available.
The researchers surmised that because the male birds more consistently ate these blister beetles than the females, it was part of a mating ritual. The researchers also found that during mating, male birds present their cloaca to female birds, and the female birds in turn carefully inspected the male's cloaca. The cloaca is the opening of a shared intestinal, reproductive and urinary tract in some species of birds. This presenting and inspection of the cloaca is a mating behavior only ever observed in this species of bustard birds, and some other bustard bird species.
The researchers suggested that the male birds may be self-medicating themselves with cantharidin to clean their cloaca of parasitic infections to make themselves appear more attractive during mating. When the female bird inspects the cloaca and sees that it is clean of parasitic infection, she knows that she is less likely to receive a sexually transmitted disease from the male. Parasitic infections can produce symptoms visible in the cloaca, like tapeworms or diarrhea, which can be seen against the white feathers that surround the male cloaca.
Scientists have already observed other large birds self-medicating with toxic beetles to clear parasitic infections. However, this is the only proposed case of male birds self-medicating with toxic beetles to enhance their courtship. If this turns out to be true, it would be the first recorded case of a species of bird doing this.
However, the findings are far from definite.
"What they're suggesting is a cool idea, but that's all it is at this point. As they acknowledge in the article, they really can't show a connection between mating success and this behavior in males," said Daphne Fairbairn, a biologist at the University of California at Riverside, who did not participate in this study.