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Nebraska predators animals1/8/2024 ![]() Researchers can use this information to estimate an animal’s ranking in a local food web. Heavier nitrogen atoms persist and accumulate through the food web, meaning that predators tend to contain more of those isotopes than their prey. To overcome this obstacle, the researchers analyzed the ratio of lighter versus heavier nitrogen atoms, or isotopes, in the tissue samples of every wolf spider they collected. The research team faced a challenge in capturing spider-on-spider predation due to difficulties in distinguishing among the DNA of wolf spider species. But it turns out that they overlap a lot.” Overcoming an unexpected challenge “You would expect that to reflect in their diet somehow. “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. Contrary to the team’s expectations, the diet of any one wolf spider species mostly resembled that of the others, shedding light on the complex dynamics of these predators’ food web. Uiterwaal also developed a mathematical method that helped the team determine how much of each prey a spider had consumed. To analyze the actual diets of 605 wolf spiders, the researchers employed sophisticated techniques, such as analyzing the DNA of the spiders’ digested food to identify unique barcodes corresponding to each type of prey consumed. We’ve even seen spiders out there eating toads.” Using DNA to determine exactly what the spiders ate Uiterwaal commented, “You name it, and they’ll eat it. Many of the captured insects and arachnids were part of the wolf spider diet, which included flies, grasshoppers, crickets, butterflies, moths, aphids, and other spiders. In order to accurately count the prey, Uiterwaal used a novel method of placing hollow wooden boxes onto unsuspecting plots of earth and then vacuuming up every ground-bound and flying insect within. To investigate, 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,” said Uiterwaal. 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. She and her colleagues, including doctoral adviser John DeLong, noticed that multiple local wolf spider species seemed to be defying an ecological principle by occupying more or less the same niche within the same habitat. The study was inspired by Uiterwaal’s observations 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.” How the study was done ![]() “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. Stella Uiterwaal, who led the study while earning her doctorate at Nebraska, explains that predators that occasionally kill and eat their more competitive peers could benefit in a couple of ways that act as an “equalizing mechanism.” However, the researchers found that when the diversity of mutual prey is limited, wolf spiders in Nebraska may turn to eating one another in order to maintain equilibrium.Ī decline in prey variety often spells trouble for weaker predators, as it puts them into direct competition with their stronger counterparts. ![]() ![]() ![]() Maintaining equilibrium by eating your neighbors This distribution of resources reduces competition and ensures enough prey for all predators involved. This phenomenon could contribute to the maintenance of an ecological balance among these arachnid predators.Įcologists have long understood that predators with similar diets can coexist by effectively sharing the food sources within a community. A recent study from the University of Nebraska-Lincoln has revealed that a limited menu of prey in an ecosystem may lead to wolf spiders of multiple species dining on each other and even resorting to cannibalism. ![]()
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