P. sulcatus are active crawlers and foragers of microalgae covering over the substrates (Houbrick 1987). Crawling is achieved by retrograde, ditaxic wave movement of the foot (Houbrick 1987). Like all planaxid snails, P. sulcatus frequently touch the substrate with their long tapering cephalic tentacles one at a time, waving back and forth in a rhythmic manner (Houbrick 1987). This behavior was described as being unique to members of the Planaxidae among other Cerithiaceans (Houbrick 1987).

The ventral-lateral position of the eyes on the tentacle bases, places them close to the substrate thus, enabling the animal to see the substrate at all times while moving (Houbrick 1987). The large extended oral hood at the snout tip is also in constant contact with the substrate while crawling, moving left and right in a vacuum cleaner fashion to allow for constant grazing on microalgae such as Entophysalis deusta, Callothrix crustacea, Schizothrix arenaria and Kyrtuthrix maculans growing on the substrates (Houbrick 1987; Rohde 1981). All Planaxidae species are thought to be photonegative, being only active at night and on overcast days (Houbrick 1987). However, P. sulcatus are frequently observed being exposed on rocks during low tides and hence does not appear to be as photonegative as compared to other members of  the Planaxidae family (Houbrick 1987; Rohde 1981).

Planaxis sulcatus in actively crawling state.  Note the
extended cephalic tentacles at the anterior of the animal
used for sensing their environment.