To account for it, she and the team also analyzed the ratio of lighter vs. Just one problem: Given the challenges of distinguishing among the DNA of wolf spider species, Uiterwaal knew the barcoding would struggle to capture any spider-on-spider predation. Their discovery did leave open the possibility of a spider-eat-spider world. But it turns out that they overlap a lot.” “You would expect that to reflect in their diet somehow. Uiterwaal“All these spiders are essentially eating the same things - which I wasn’t expecting, because you do find these spiders in slightly different places, and they look different, and they have different behaviors,” Uiterwaal said. Uiterwaal also applied a mathematical method - one she developed - that helped the team ascertain how much of each prey a spider had consumed.Ĭounter to the team’s expectations, the diet of any one wolf spider species mostly resembled the others. One of those techniques involved analyzing the DNA of the spiders’ digested food in search of barcodes: DNA sequences unique to each type of prey the spiders consumed. Still, cataloging the actual diets of 605 wolf spiders would require more sophisticated techniques. “We’ve even seen spiders out there eating toads.” The team spots a wolf spider on one of its nightly expeditions to collect the nocturnal predator. “You name it, and they’ll eat it,” Uiterwaal said. Many of the captured critters also appeared on the wolf spider menu: flies, grasshoppers, crickets, butterflies, moths, aphids and, yes, other spiders. Wanting to get as accurate a count of that prey as possible, Uiterwaal took to plopping hollow wooden boxes onto unsuspecting plots of earth, then using a customized vacuum to suck up every ground-bound and flying insect within. So the researchers spent two summers collecting specimens of eight wolf spider species and their potential prey. If that happens, they won’t be able to persist in the environment for very long.” “And there’s this classic ecological idea that species can’t be doing the exact same thing. “We noticed that there are so many different wolf spider species that all seem to be doing the same thing,” Uiterwaal said. Dusk descends on Cedar Point Biological Station, a field research site near Ogallala, Nebraska. It was there that she and some colleagues, including doctoral adviser John DeLong, realized that the wealth of local wolf spider species seemed to be defying an ecological principle by occupying more or less the same niche of the same habitat. The study originated from what Uiterwaal observed while studying and later teaching at Cedar Point Biological Station, a lake-adjacent field site in southwest Nebraska.

“And you’re also reducing the population size of that better predator, so you have fewer of them to compete with.” “Some of your diet is now coming from that other predator, instead of the shared prey that you’re competing for,” said Uiterwaal, now a postdoctoral researcher at Washington University in St. Predators that do manage to at least occasionally kill and eat their more competitive peers, though, could benefit in a couple of ways that collectively act as an “equalizing mechanism,” she said. But analyses of wolf spider species in Nebraska suggest that when the diversity of their mutual prey is lacking, the eight-legged predators might instead maintain an ecological equilibrium, in part, by eating one another.Ī decline in the variety of prey should spell bad news for weaker predators, which are then put into more direct competition with their stronger counterparts, said Stella Uiterwaal, who led the study while earning her doctorate at Nebraska. STUDY SUGGESTS WOLF SPIDERS MAY TURN TO CANNIBALISM, PREYING ON RELATED SPECIESĪ limited menu of prey may weave a tangled food web by emboldening wolf spiders of multiple species to dine on each other and even cannibalize their own, says a study from the University of Nebraska–Lincoln.Įcologists have long known that predators with otherwise-similar diets can coexist by effectively divvying up the food sources of a community to ease competition and, ideally, leave enough prey for everyone.

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