Environmental demands that require intensive search for mates, food and nes
t sites are correlated with efficient spatial memory in many mammalian and
avian species. This convergence of evidence has led to the view that spatia
l memory, and the neurological structures associated with it, have been sel
ected in niches that require memory for the location,of goal objects. Wheth
er such evolutionary demands are also correlated with nonspatial abilities
that require flexible use of associations similar to those required for spa
tial memory has not been well studied. In addition, correlations between ni
che types and the use of spatial or nonspatial memory have not been investi
gated in nonmammalian, nonavian taxa. In this study, we investigated the re
lationship between foraging strategies and performance on two; tasks, one s
patial and the other nonspatial, in congeneric lizard species: Acanthodacty
lus boskianus, an active forager that collects clumped sedentary prey, and
Acanthodactylus scutellatus, a sit-and-wait predator that collects distribu
ted mobile prey. The two species did not differ in their performance of a s
patial memory task, but A. boskianus, the active forager, performed better
on the reversal of a visual discrimination, a nonspatial task. These findin
gs question the generality of the spatial adaptation model for vertebrates.
We present the pliancy hypothesis, which we developed to account for these
results. (C) 1999 The Association for the Study of Animal Behaviour.