Many animals follow daily schedules or seasonal cycles—but can they distinguish, say, three seconds from 13? Some—bumblebees, pigeons, cats and others—are known to perceive passing time with some precision. After years working with the captive seals at the Marine Science Center at Germany's University of Rostock, biologist Frederike D. Hanke suspected the slippery mammals might be able to as well.
Hanke and her team tested her hunch on Luca, an 11-year-old harbor seal at the center. They displayed a white circle on a black computer screen for a period of three to 30 seconds, paused and then flashed the circle again. The researchers trained Luca to press one button if he thought the second display was longer and another if he thought both displays were of equal length. When he was correct, he enjoyed a tasty herring treat.
The team found that Luca could detect differences as short as 420 milliseconds. In other words, he could distinguish a three-second display from one lasting 3.42 seconds. His precision weakened as the pairs of display durations got longer, however. The experiment's results were recently published in Animal Cognition—the first time the ability to measure time has been reported for a pinniped.
Seals may have evolved this skill to make split-second decisions while chasing fish or to identify vocalizations made at different rates by other seals, says Hanke, who is extending her investigation both to more seals and to acoustic stimuli.
Peter Cook, a psychologist at New College of Florida who has studied pinniped cognition and was not involved in Hanke's work, was most impressed by how easily Luca learned the testing task. It is common in psychophysics experiments such as this one for animals to need lots of practice—but Luca learned it in two training sessions. “Even though we're talking about very small discriminations, these short durations really pop for the seal,” he says. “It strongly suggests this is a very robust and well-tuned sense.”