Spatial and reversal learning in congeneric lizards with different foraging strategies.

Environmental demands that require intensive search for mates, food and nest sites are correlated with efficient spatial memory in many mammalian and avian species. This convergence of evidence has led to the view that spatial memory, and the neurological structures associated with it, have been selected in niches that require memory for the location of goal objects. Whether such evolutionary demands are also correlated with nonspatial abilities that require flexible use of associations similar to those required for spatial memory has not been well studied. In addition, correlations between niche types and the use of spatial or nonspatial memory have not been investigated in nonmammalian, nonavian taxa. In this study, we investigated the relationship between foraging strategies and performance on two tasks, one spatial and the other nonspatial, in congeneric lizard species: Acanthodactylus boskianus, an active forager that collects clumped sedentary prey, Acanthodactylus scutellatus, a sit-and-wait predator that collects distributed mobile prey. The two species did not differ in their performance of a spatial memory task, but A. boskianus, the active forager, performed better on the reversal of a visual discrimination, a nonspatial task. These findings question the generality of the spatial adaptation model for vertebrates. We present the pliancy hypothesis, which we developed to account for these results. Copyright 1999 The Association for the Study of Animal Behaviour.