Expression and mechanisms of behavioral plasticity in large mammals

Behavioral plasticity, the alteration of behavior in response to stimuli,
is becoming increasingly important in the context of human-induced rapid
environmental change. Theoretical and empirical studies suggest that the
expression and magnitude of behavioral plasticity are likely facilitated
or constrained primarily by two factors: environmental variation and
endogenous traits such as body size. The contextual role of these factors
on behavioral plasticity, however, is poorly understood; there are
relatively few studies that have compared the magnitude and potential
drivers of behavioral plasticity at different levels (i.e., population and
individual) across species, especially in free-ranging animals with
diverse behavioral traits such as large mammals. Here, we quantify and
test potential hypotheses for the mechanisms underpinning behavioral
plasticity at the individual and population level in response to variation
in summer temperatures for 1,068 animal years in 17 populations across 9
species of large mammals. All populations displayed behavioral plasticity
in response to increased temperatures, modifying their relative selection
for heat-relieving habitat attributes (e.g., elevation) and
heat-generating behavior (i.e., movement speed). We found strong support
for the hypothesis that the variability of the physical environment is an
important driver of behavioral plasticity—both mean population behavioral
plasticity and variation among individuals within each population in
plasticity were lower with increased heterogeneity of habitat attributes
such as tree cover. Yet, the variability in environmental conditions
(i.e., the magnitude of the temperature increase) had no effect on
behavioral plasticity within and among populations. We did not detect an
effect of endogenous traits on the expression of behavioral plasticity;
however, we note that data availability limited our tests of this
hypothesis to a select few endogenous traits (body size, feeding guild,
and sex of the tracked individuals) that predominantly vary at the species
level, for which we had 1-3 replicate populations per species. Our results
provide an integrative and generalizable understanding of the expression
of behavioral plasticity among populations of large mammals in temperate
environments and emphasize the important but nuanced role of environmental
variation in determining the scope of behavioral plasticity in these
populations.