Dermal disappearance: differences in cryptic color change in the slimy sculpin (Cottus cognatus).

Abstract

Cryptic behavior is an excellent anti-predator defense strategy, confounding search time and development of search images. Little research has been done on the effects of the presence of a predator on cryptic coloration. Our study reviewed the rate of cryptic color change in slimy sculpins (Cottus cognatus). A scale of six colors was devised to quantify color change. We characterized rates of change in two color directions: from light-to-dark (LTOD) and from dark-to-light (DTOL). Three hypotheses were tested: 1) rate of change from DTOL is different than the rate from light-to-dark LTOD, 2) small fish change quicker than large fish and 3) rate will increase in the presence of a predator. As a group, sculpins changed faster from LTOD than DTOL. Small slimy sculpins (<5.0 cm ) changed faster from DTOL and large ones (>= 5.0 cm) changed faster from LTOD. Large sculpins increased their degree of color change in the presence of predators. The different rates of color change observed are likely due to a combination of physiological and behavioral constraints.