The function of trail following in the pulmonate slug, Limax pseudoflavus

Abstract

Trail following in Limax pseudoflavus Evans is easily observable under laboratory conditions but it is less frequent in the field and its function remains unclear. In experiments allowing the choice between trails and other environmental cues slugs tended to follow trails most frequently when those trails were going in a direction close to that dictated by the other cue. Similarly trails were more often followed when approached at a narrow angle. Trail following was observed as a prelude to courtship. It is concluded that trails provide low priority directional cues and that they are only followed in the absence of other cues or when their direction closely coincides with those other cues. Trail following is a component of food finding, homing and courtship behaviour in the field, but in each case its role may be subordinate to that of airborne odours. Measurements of the quantity of mucus in the trails show that there is no reduction in the secretion of mucus while trail following. Trail following cannot therefore be seen as a mucus-saving tactic.