Master student (Department of Life Sciences, National Chung-Hsing University, Taiwan)
Change or die? Inconsistent decoration building in Argiope spiders
Animals would convey visual, olfactory or auditory deceptive signals to mislead their prey or predators to act in ways that are beneficial to these signalers. However, when these deceptive signals are widely present in the environment their consistency and predictability may render them detected by receivers and consequently lower the fitness of the signalers. In this study, I investigated how animals change frequency and form of a deceptive signal to solve such problem. Previous studies showed that silk decorations built by Argiope spiders is a deceptive signal functioning to lure prey but at the cost of attracting unwelcome predators to the spiders simultaneously. Numerous field observations showed that the individual spiders would change the occurrence and arrangement of decoration bands on webs on a daily basis. Since the visually conspicuous decorations play a foraging role in this sit-and-wait predator, I hypothesize that pressures from prey and predators interplay to generate inconsistent web decorating behavior in Argiope spiders. Previous studies suggested that the pollinator insects may use consistent decoration form to avoid spider webs at a certain location and therefore changing decoration occurrence and form may lower the learning efficacy of insects. In this study I manipulated frequency and form of decorations by a dummy approach to evaluate whether Argiope spiders’ inconsistent visual signaling is an optimal strategy. I used cardboards with chromatic properties similar to corresponding spider body color and decorations to construct dummies and the frequency and orientation pattern of dummy decorations were manipulated in the field. There were a total of six treatments and video cameras were used to monitor the responses of prey and predators to them. The results showed that no matter decoration form was variable or fixed those in high frequency group can attract more prey. When decorations occurred inconsistently and frequently insect attraction rate was the highest. Dummy decorations in high frequency group also attracted more unwelcome predators. However, when the decoration form varied the predator attraction rates decreased. These results imply that building decorations more frequently and inconsistently could help Argiope spiders to lure prey and mislead the predators simultaneously. My results thus demonstrate that inconsistent decoration building is an optimal signaling strategy for Argiope spiders.
Updated: Mar-10-2014 01:22:51 (Taiwan, GMT+08:00).