The heritability of fear: decomposing sources of variation in marmot flight initiation distance

Abstract

A variety of intrinsic and extrinsic factors shape an animal's antipredator behaviour. Flight initiation distance (FID) is a common way to evaluate antipredator behaviour and is used to assess an individual's shyness or boldness. Numerous FID studies, in a variety of taxa, have shown that FID is a decision that is sensitive to both the costs and benefits of flight. While there is some evidence that individuals may have repeatable FIDs, and there are several genes associated with FID (DRD4 and SERT), few studies have quantified the genetic variance of FID. Knowledge of genetic basis permits us to understand the evolutionary potential of a trait within a population, and heritable variation is yet another mechanism that enables animals to respond to a dynamically changing world. Here we conducted a variance decomposition analysis using the quantitative genetic mixed model (i.e. the ‘animal model’) to identify the degree to which genetic and nongenetic factors explained variation in FID within a population of wild yellow-bellied marmots, Marmota flaviventer. Within our 18-year data set of individually marked individuals, we found significant heritable variation for FID that we estimated at 0.15. These results demonstrate that genetics, in addition to environmental factors, influence an animal's fear response. Understanding evolvability and plasticity of FID could have important implications for conservation.