Becoming creatures of habit: among‐ and within‐individual variation in nesting behavior shifts with age

Becoming creatures of habit: among‐ and within‐individual variation in nesting behavior shifts with age:

Abstract

The quantification of repeatability has enabled behavioral and evolutionary ecologists to assess the heritable potential of traits. For behavioral traits that vary across life, age‐related variation should be accounted for to prevent biasing the microevolutionary estimate of interest. Moreover, to gain a mechanistic understanding of ontogenetic variation in behavior, among‐ and within‐individual variance should be quantified across life. We leveraged a 30‐year study of painted turtles (Chrysemys picta) to assess how age contributes to variation in the repeatability of nesting behaviors. We found that four components of nesting behavior were repeatable, and that accounting for age increased the repeatability estimate for maternal choice of canopy cover over nests. We detected canalization (diminished within‐individual variance with age) of canopy cover choice in a reduced dataset despite no shift in repeatability. Additionally, random regression analysis revealed that females became more divergent from each other in their choice of canopy cover with age. Thus, properly modeling age‐related variance should more precisely estimate heritable potential, and assessing among‐ and within‐individual variance components in addition to repeatability will offer a more mechanistic understanding of behavioral variation across age.