Harvestmen are fearful in the light but not the darkness

Abstract

The defenses of harvestmen encompass nipping with spines, releasing of chemicals, fleeing, bobbing, crypsis, and death feigning. Animals are expected to invest more in death feigning in situations in which they are more vulnerable to predation. For prey species attacked by visually-oriented predators, death feigning should be more frequent in daytime than during nighttime. Here, we used the harvestman Mischonyx cuspidatus (Roewer, 1913) (Gonyleptidae) to test whether: (i) individuals perform death feigning during daytime more often than during nighttime; (ii) individual body condition influences the time and frequency of death feigning. We found support for the former prediction, but not for the latter. Our results are in accordance with the hypothesis that among harvestman death feigning would be an advantageous passive defense against visually oriented predators. In this study, for the first time, we demonstrate that harvestmen show differences in death feigning behavior depending on light conditions.