Male spiders manipulate females by producing a vibratory shudder that significantly delays the female’s predatory behaviour even when the female is tempted by live prey. The findings are presented in the journal Scientific Reports this week.
Male Argiope spiders produce distinctive courtship vibrations (shudders) when they enter a female’s web. Males shudder by quickly rocking on the web several times, creating a distinctive vibration pattern, and there tends to be a concentrated burst of shuddering during the earliest and riskiest phase of courtship when the male moves across the web to make contact with the female at the central hub. These vibrations seem to reduce the risk of pre-copulatory cannibalism, but the signals underlying this have remained uncertain.
Anne Wignall and Marie Herberstein tested whether male shudders delay female predatory behaviour in the presence of live prey. They presented a live cricket to female spiders during the playback of either shudder vibrations or white noise, and compared the responses to a control in which a live cricket was presented with no playback vibrations. They found that females were much slower to respond to crickets during playback of shudder vibrations. Shudder vibrations also delayed female predatory behaviour in a related spider species, showing that the vibrations do not simply function for species identity.
The study challenges the assumption that courtship vibrations are species-specific and function to allow the male to ‘prove’ his species. Instead, the first courtship signal that males produce seems to be generic and its main role is to suppress female aggression.