Carcass scavenging relaxes chemical-driven female interference competition in flour beetles

Female-female nonsexual interference competition is a major fitness determinant of biased sex-ratio groups with high female density. What strategies can females use to overcome the negative impact of this competition? We used flour beetle Tribolium castaneum to answer this question, where competing females from female-biased groups were already known to suppress each other’s fecundity by secreting toxic quinones from their stink glands, indicating a unique chemical-driven interference competition. Surprisingly, increasing resources did not alleviate these fitness costs. Females also did not disperse more from the site of interference competition. Hence, the competition was neither influenced by the total resource availability nor the lack of opportunity to avoid chemical interference. Instead, protein sequestered via scavenging of nutrient-rich carcasses relaxed female competition, by increasing their fecundity and reducing the quinone content. Finally, stink gland components themselves...