Abstract
This study investigated whether
the escape behaviour of lizard species could be predicted by knowledge
of their functional capabilities. In the laboratory, the effect of
perch diameter support on sprinting and jumping ability was measured in
five species of Anolis lizards. In all species, sprint speed
declined with decreasing perch diameter, but decreased perch diameter had
little effect on jumping ability. The escape behaviour of a lizard
on a particular-sized support in nature was then evaluated as a function
of the lizard's sprinting and jumping capabilities. As diameter decreased,
lizards in all but one species tended to escape by jumping more frequently
because jmping ability is less affected by diameter than is sprinting ability.
It was also predicted that species in which running ability declines greatly
as diameter decreases should switch to escape by jumping more often than
species that experience less of a decline in running ability. This
prediction was not confirmed. Consequently, functional capabilities
play a role in determining escape behaviour in Anolis lizards, but
other factors may be important as well.
Non-Technical Summary
Lizards differ in their maximal sprinting and jumping abilities. Moreover, within a species, these abilities are affected by the surfaces on which they occur. Do differences in these abilities affect lizard behavior? We tested this hypothesis by examining the manner in which five species of Anolis lizards escaped from a human predator. In the laboratory, we measured the sprinting and jumping ability of these species on supports differing in diameter. Then, we went into the field and approached lizards on a variety of different surfaces to determine whether they escaped by running or jumping.
In all species, maximal sprint speed was affected by surface diameter: as diameter decreased, so did sprinting ability. However, the extent to which speed was affected by diameter differed greatly among species. By contrast, diameter had a negligible effect on jumping ability.
From these observations, we made two predictions. First, within a species, the tendency to escape by jumping should increase with decreasing perch diameter. The rationale is that, because sprinting ability declines with perch diameter but jumping ability doesn't, lizards should shift to jumping as diameter decreases. This prediction was confirmed in all species but one (which displayed a non-significant trend in the same direction).
Our second prediction
is that the extent to which species shift to jumping should correspond
to the extent to which sprinting ability declines as a function of surface
diameter. The rationale is straightforward: the greater sprinting
ability is impaired, the more likely they should be to shift to jumping
on narrow surfaces. This prediction was not confirmed. Hence,
although functional capabilities play some role in determining escape behavior,
other factors must be important as well.