Eavesdropping Predators

Many social interactions between insects involve the use of plant-borne vibrations. Many insects and spiders have evolved the ability to generate patterns of vibrations allowing them to communicate with potential mates or members of the same social group. It is now being researched that some spiders are able to forage through this form of communication. The predators use the vibrations that prey, such as the leafhopper, give off to track them down and consume the individual.

When leafhoppers and other such species send out vibrations along the leaf they increase the likelihood that a predator would pick up on these vibrations, managing to find the individual whom is sending out the vibrations. It has been known already that predators can exploit sight sound and smells of their prey but the fact that predators can pick up on vibration signals is a recent discovery.

By using molecular diagnostic methods with leafhopper specific primers it has been found that one species of spider is a frequent predator of the leafhopper. Predation was found to be much higher in sexually mature leafhoppers compared to the young leafhopper forms. These vibrations were once believed to be a private communication channel allowing a male to signal a female yet some predators can use these signals to track down the prey and eat it. The use of vibrations as a way to call a mate is why it is believed that younger forms of leafhoppers are not preyed on as greatly, as they do not give off the vibrations.  It was also found that males were consumed far more than females, which is believed to occur as the males are the individuals that give off the vibrations calling the females in, putting the males at a higher risk.

                                                                                    

An important question in the study of predator eavesdropping is how a particular signal in the environment becomes a foraging cue. Due to sexual selection there is an amazing amount of variety in the type of signals insect species use. For specialists the signals given off that guide the individuals to the prey may be predictable enough that natural selection can shape responses not dependent on experience. On the other hand for generalist’s predators they will have to learn the signals and gain experience to be able to track down their prey. Just like colouration is a warning signal for predators, some vibration signals may play a similar role allowing predators to learn which signals to track down and which to avoid.

Overall, little is known about the how predators use vibrations to track down their prey and the responses in which predators make remain speculative. As a greater amount of research goes in to deciphering the extent to which predators use the prey vibrations, the speculation will surely change.

Links

http://news.bioscholar.com/2011/03/killer-spiders-prey-on-insects-that-use-vibration-to-woo-mates.html

Cocroft, R. B. (2011) The public world of insect vibrational communication. Molecular Ecology, 20, 2041-2043.