Prey tell: New method could streamline estimates of predator-prey relationships

Welcome to Pocket Science: a glimpse at recent research from Husker scientists and engineers. For those who want to quickly learn the “What,” “So what” and “Now what” of Husker research.

What?

Determining how a predator’s food consumption fluctuates with the availability of its prey — its so-called functional response — can help predict population dynamics, assess the stability of ecosystems and answer myriad other questions.

Ecologists usually study functional responses by introducing one predator to an area, dropping in a certain number of prey, and recording how many prey the predator consumes over a given time. They then repeat the trial with new predator specimens and varying densities of prey. Though effective, the method can require large numbers of animals and experimental observations. Those logistical challenges also make it difficult to answer certain questions all together.

So what?

Nebraska ecologists Kyle Coblentz and John DeLong addressed the shortcomings by developing an experimental design and statistical analysis that can estimate a functional response from just one type of data: the time between a predator’s feeding events.

Coblentz and DeLong derived their method from existing equations that factor in how frequently a predator finds and kills prey, along with how long the predator needs to capture and consume it. The duo found that knowing the amount of time between feedings can be used to statistically infer the frequency of successful attacks for a given area and density of prey, even as that density changes over time.

Statistical simulations mostly supported the validity of the duo’s new method. The method’s estimates generally matched up with the results of a feeding experiment involving bold jumping spiders, too.

Now what?

By saving time and resources, the method could help ecologists investigate elusive issues: the predator-prey dynamics of rare species, for instance, or varying functional responses within a species.

One potential application? Estimating functional responses of difficult-to-track marine species by fitting them with accelerometers, which prior research has shown can be used to identify feeding events.