How predators use vibrational signals to home in on their prey
Killer spiders are playing havoc with insects that use vibration to attract a mate, a Cardiff University–led research study shows. Funded in part by the BREAKING THE CODE ('Breaking the code: interception and exploitation of intraspecific vibrational communication between insects by generalist predators') project, which clinched a Marie Curie Intra—European Fellowships grant worth almost EUR 229 000 under the EU's Sixth Framework Programme (FP6), the study is presented in the journal Molecular Ecology.
Entomologists at the Cardiff School of Biosciences at Cardiff University in the UK investigated how leafhoppers and other insects are at risk of being eaten alive when they use vibrations to charm a mate. Predatory spiders intercept the signal in order to isolate their victim.
Experts have long known that predatory spiders use their prey's sight, sound and smell communications to their advantage. This latest study provides new insight into spider behaviour, suggesting that predators including spiders have the capacity to pick up secretive vibrational signals and use them to identify prey.
'Vibrational signalling is a widespread form of sexual communication between animals,' explain Dr Meta Virant—Doberlet from the Department of Entomology at the National Institute of Biology in Slovenia, and Professor William Symondson of the Cardiff School of Biosciences.
'By observing this behaviour we have been able to see, for the first time, that spiders are able to exploit sexual vibrational communication signals as a mean of tracking down their prey,' the authors of the study say.
Evaluating the behaviour of the spider species Enoplognatha ovata, a relative of the infamous Black Widow spider that despite being small is a formidable predator able to kill insects many times its size, the researchers found that when recordings of male leafhopper vibrational signals were played, the spiders picked up the signal and launched a food hunt. The team also discovered that the spiders favoured male leafhoppers rather than female. They suggest that the more complex and noisy signals used by males during courtship work against them.
Despite vibrational signalling not being unique feature among animals, it is the first time that scientists have succeeded in showing that predators exploit their victims' signals to find and kill them. According to the team, their latest discovery will stimulate interest and lead to a new field of study.
'Predators have evolved to intercept the signals of their prey but until now this was thought to be limited to visual, acoustic and chemical ways of communicating,' say Professor Symondson and Dr Virant—Doberlet. 'This new discovery represents a previously overlooked strategy for prey location and a major unrecognised driver in the evolution of both predators and prey,' they add.
'This is a very significant scientific advance, opening up a whole new area for scientific investigation. Vibrational signalling is widespread amongst invertebrates and it is highly likely that many predators have evolved to exploit it.'
The mechanism used to locate prey has the potential to be a major unrecognised driver of evolution in both predators and prey, say the researchers.