Female fruit flies' levels of aggression soar after sex, when a variety of proteins, which flow freely in semen, stimulate dramatic behavioural and physiological changes in females. Other changes include increased ovulation, rejecting male advances and loss of interest in sex. Increased post coital levels of aggression may have wider in direct implications on female competition.
Studies in many species have shown an association between increased levels of aggression in females, egg laying and reproduction. Protecting and providing for offspring is often identified as the main motivation for this behaviour. The factors at play in the reproductive process, that trigger such dramatic behavioural changes, have until now, been less clearly understood.
A team of researchers led by Dr Eleanor Bath and Dr Stuart Wigby of the Oxford University Department of Zoology, examined hundreds of fruit flies, assessing the impact of mating on female fruit fly behaviour, and to what degree it alters their levels of aggression. Fruit flies are also known as Drosophila melanogaster, a species of fly that is approximately one-eighth of an inch in length, with red eyes. Fruit flies are known for being drawn to ripe or rotten foods like fruits and vegetables.
The research newly published in Nature Ecology & Evolution, proposed that aggression was potentially stimulated by two factors; either indirectly as a result of costly egg-production, or directly by coming into contact with the components contained in the male’s ejaculate. The findings show that after mating, female fruit flies become evidently more aggressive towards each other when fighting over food, often head-butting and swatting at each other. Specifically, pairs of mated females fought significantly more than virgin pairs. Pairs with at least one newly mated female were also found to be more aggressive towards each other than pairs with two virgin females.
Learn more about aggression in female fruit flies in the video below:
A lot is known about male fruit fly behaviour and what affects their levels of aggression, but very little has been published about competition among females. Even taken on its own, our study is useful. If these behavioural changes occur in fruit flies, it is highly likely that they are happening in other insects.- Dr Stuart Wigby, Research Fellow in the Department of Zoology
Copulation may also affect the social tolerance of females in general. Immediately after mating female fruit flies are known to be significantly less receptive to re-mating. Females were found to be equally aggressive towards one another, regardless of whether or not they were able to produce eggs, showing that reproduction was not a contributing factor in their obvious change of temperament.
Dr Stuart Wigby added: ‘A lot of insect control programmes involve releasing sterile males into the wild. When these males mate with wild females, the females fail to produce viable offspring. It could be that mating with these sterile males also affects female aggression levels. Further research will help us to understand exactly how such affects could help or harm populations, and therefore whether or not they can have a wider use.'
Story courtesy of the University of Oxford News Office