Scientists discover that the most efficient foraging methods can lure predators.

Scientists at the University of Bristol have discovered that animals that use the most efficient methods of foraging may well pay for it.

Results published today in Behavioral ecologyreveals why animals do not always use a search strategy that maximizes results.

How animals move through their habitat, particularly in search of food, is a major question in biology, and has application in how animals respond to environmental change.

Several studies have shown that a special type of movement, known as Levi’s movement, increases the ability to find resources because it involves long-distance movements between foraged areas, as well as periods of focused searching in one area. It has also been shown that a group of animals use this type of locomotion.

This study is the first to demonstrate the potential cost of Levi’s motion in an experiment, showing that prey using Levi’s motion targets twice as many prey as using Brownian motion—the motion observed for molecules in a gas and thus a primary predictor.

“We have shown that this is because predators prefer to target prey that moves with straighter locomotion paths, possibly because this makes the future position of the prey more predictable,” explained Professor Christos Ioannou from Bristol’s School of Biological Sciences.

Professor Ioannou and his team used a virtual prey approach. They have developed computer simulations of prey that are identical in size, colour, speed, etc., but differ in how they rotate.

The video was then played on stickleback fish in a tank by projecting the video onto a transparent screen. This allowed the fish to see the prey, and for the researchers to capture and record their choices.

“By using an experimental design that presents virtual prey on screen to real predators, we can control everything about the prey and isolate the variable we’re interested in – here, locomotion – while also using real animals,” Professor Ioannou continued.

This study demonstrates that predators may not always use a search strategy that maximizes resource finding because there may be costs that were unknown prior to the study. This may explain why some studies have found that animals use different types of searching than Levi’s locomotion.

He added, “Our study shows, for the first time, that animals that use a common and highly efficient method of foraging may actually pay the cost of being more vulnerable to predators.”

“Going forward, we want to look at whether stickleback prey exhibits Leviform or Brownian motion.”

“More broadly, our study predicts that apex predators should be less likely to exhibit fibrous locomotion than apex predators.”