For a staged predator-prey cage match, the team placed six crickets "in the ring"a container with enough natural airflowagainst just one solitary spider. The ring was left alone for one week, and cricket mortality rate was measured daily. To accurately determine the crickets' precise cause of death, the team measured cricket mortality rate both in the presence and absence of spiders.
Using their collected data, the Pitt researchers modeled the behaviors of both species, hypothesizing potential outcomes. In addition to their behavioral data, they also took into account the spiders' and crickets' body mass, body conditions, and their individual responses to threats.
Their results closely matched the predictions of the locomotor crossover hypothesisa theory positing that active predators tend to consume inactive prey, whereas inactive predators tend to consume active prey. Pruitt said this finding is actually surprising, given the possibility that the predators and/or prey could have changed their behavioral responses based on their foes' activity levels.
"This implies that the personality types of these spiders and crickets are fairly rigid," said Pruitt. "If either species had been more flexible, they might have sensed the personality types present in their foe and shifted their strategy more strategically."
Their results show that the performance of the spiders depended neither on the average activity level of the spider nor the average group activity of the crickets. Instead, it was the interaction between the activity levels of both groups that predicted survival for the crickets and foraging success for the spiders.
"Our study is one of
|Contact: B. Rose Huber|
University of Pittsburgh