Algorithmic behaviour and spatial memory are used by two intertidal fish species to solve the radial maze

We used an eight-arm radial maze to assess the relative contributions of le arned patterns of movement (algorithmic behaviour) and spatial memory to th e foraging efficiency of two sympatric rocky-shore fish, fifteen-spined sti ckleback, Spinachia spinachia, and corkwing wrasse; Crenilabrus melops, exp loiting nonrenewable food sources. To forage efficiently, subjects had to a void arms already depleted within a trial. In the absence of spatial cues, sticklebacks and wrasse improved their foraging efficiency by developing th e algorithm of visiting every third arm. In the presence of spatial cues (c oloured tiles) algorithmic behaviour was largely subsumed by the use of spa tial memory. Imposition of a delay within trials reset the behavioural algo rithm, so depressing foraging efficiency in the absence of cues, but not in their presence when memory could be used to guide behaviour. Memory retent ion for previous choices (working memory) lay within the range 0.5-5.0 min, consistent with the characteristic timescale expected for habitats where p rey distribution changes rapidly during the tidal cycle. We considered two hypotheses on the type of information memorized: the cue list hypothesis an d the spatial configuration hypothesis. The cue list hypothesis predicts th at neither random repositioning nor fixed rotation of spatial cues should i mpair foraging efficiency, whereas the spatial configuration hypothesis pre dicts that efficiency should be impaired by random repositioning of cues bu t not by rotation. Data supported the spatial configuration hypothesis. (C) 1999 The Association for the Study of Animal Behaviour.