Fitness, risk taking, and spatial behavior covary with boldness in experimental vole populations

Abstract

Individuals of a population may vary along a pace‐of‐life syndrome from highly fecund, short‐lived, bold, dispersive “fast” types at one end of the spectrum to less fecund, long‐lived, shy, plastic “slow” types at the other end. Risk‐taking behavior might mediate the underlying life history trade‐off, but empirical evidence supporting this hypothesis is still ambiguous. Using experimentally created populations of common voles (Microtus arvalis)—a species with distinct seasonal life history trajectories—we aimed to test whether individual differences in boldness behavior covary with risk taking, space use, and fitness. We quantified risk taking, space use (via automated tracking), survival, and reproductive success (via genetic parentage analysis) in 8 to 14 experimental, mixed‐sex populations of 113 common voles of known boldness type in large grassland enclosures over a significant part of their adult life span and two reproductive events. Populations were assorted to contain extreme boldness types (bold or shy) of both sexes. Bolder individuals took more risks than shyer ones, which did not affect survival. Bolder males but not females produced more offspring than shy conspecifics. Daily home range and core area sizes, based on 95% and 50% Kernel density estimates (20 ± 10 per individual, n = 54 individuals), were highly repeatable over time. Individual space use unfolded differently for sex‐boldness type combinations over the course of the experiment. While day ranges decreased for shy females, they increased for bold females and all males. Space use trajectories may, hence, indicate differences in coping styles when confronted with a novel social and physical environment. Thus, interindividual differences in boldness predict risk taking under near‐natural conditions and have consequences for fitness in males, which have a higher reproductive potential than females. Given extreme inter‐ and intra‐annual fluctuations in population density in the study species and its short life span, density‐dependent fluctuating selection operating differently on the sexes might maintain (co)variation in boldness, risk taking, and pace‐of‐life.

Risk assessment for Birds and Mammals

“…In enclosure studies, a semi‐field area is built in order to study an effect in the absence of confounding variables (Boonstra and Krebs, 1977; Gaines et al., 1979; Schauber et al., 1997; Hahne et al., 2011; Jochym and Halle, 2013; Eccard et al., 2022). Voles and other small mammals have been the most frequently studied species.…”

The timid invasion: behavioural adjustments and range expansion in a non-native rodent

“…Recent growth in the study of inter-individual variation in behaviour [4][5][6], however, revealed that behaviour is not entirely flexible [5], and that individuals differ consistently in behavioural traits within a population [7]. Further, this consistent variation has fitness consequences [8,9]. For the success of biological invasions of animals, two contrasting concepts have been suggested: behavioural invasion syndromes and behavioural flexibility [10], i.e.…”

“…Further, knowing that in many species males and females differ in space use and dispersal tendency [32][33][34] we assumed that the sexes may be exposed to differential selection pressures during the process of population expansion. With space use being closely related to behavioural traits [9,25], selection on space use and dispersal traits may produce spatial sorting patterns in personality traits differing among males and females. We therefore (c) investigated interactions of sex and expansion zone on the behaviour of the phenotyped individuals.…”

The timid invasion

“…Recent growth in the study of inter-individual variation in behavior (4, 5, 6), however, revealed that behavior is not completely flexible (5) and that individuals differ consistently within a population (7). Further, this consistent variation has fitness consequences (8, 9). For the success of biological invasions of animals, two contrasting concepts have been suggested: behavioral invasion syndromes and behavioral flexibility (10).…”