INVESTIGATION OF THE CRITICAL FREQUENCY OF FLICKER FUSION IN GRAY SEALS (HALICHOERUS GRYPUS FABRICIUS, 1791) IN CAPTIVITY

A group of 10 gray seals (Halichoerus grypus Fabricius, 1791) of different sexes and ages were trained to select and indicate by touch one of two demonstrated similar light sources. The animals had to touch an object with a flashing light and ignore the constantly glowing object. To determine near the threshold values of perception, the frequency of flickering was gradually increased until the proportion of correct choices did not decrease below 75%. During the experiment, it was found that the seals studied are able to distinguish flashes in the range of 23–47 flashes per second. Individual features, dependence on the level of illumination, time of year and age are revealed.