Becoming creatures of habit: Among‐ and within‐individual variation in nesting behaviour shift with age

Abstract

The quantification of repeatability has enabled behavioural and evolutionary ecologists to assess the heritable potential of traits. For behavioural 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 behaviour, 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 behaviours. We found that four components of nesting behaviour 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 data set 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 modelling 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 behavioural variation across age.

Development of “personality” in the domestic cat: A longitudinal study

“…With this caveat, the age-related decreases in within-individual variance relative to among-individual variance are consistent with previous findings in mosquitofish Gambusia holbrooki (Polverino et al, 2016), painted turtles Chrysemys picta (Delaney et al, 2020), great tits…”

“…With this caveat, the age‐related decreases in within‐individual variance relative to among‐individual variance are consistent with previous findings in mosquitofish Gambusia holbrooki (Polverino et al., 2016), painted turtles Chrysemys picta (Delaney et al., 2020), great tits Parus major (Thys et al., 2021), red knots Calidris canutus (Kok et al., 2019), and red squirrels Tamiasciurus hudsonicus (Martinig et al., 2021). When organisms face stable conditions resulting in predictable environmental cues, stabilizing trait expression (canalization) can occur, favoring stability of behavior (Kok et al., 2019).…”

Age Predicts Risky Investment Better Than Residual Reproductive Value

“…Maternal identity accounted for an additional 27%-29% of variation in distance to water, which indicates that the distance females prefer to nest from water is repeatable and likely heritable. Previous work on this population (Janzen and Morjan 2001;Valenzuela and Janzen 2001;McGaugh et al 2010;Delaney et al 2020a) and more broadly in taxa with environmental sex determination (reviewed in Janzen et al 2019) has also found that nesting behaviors can be repeatable and heritable. Our findings are congruent with this work and, given that nest distance to water is under selection (Kolbe and Janzen 2002;Delaney and Janzen 2020), suggest that the distance females nest from water should be a responsive target of selection.…”

“…Our findings instead suggest that poorer-quality individuals are unable to initiate reproduction until later ages and are more likely to perish sooner in life compared with higher-quality females (Cichon et al 1998). As noted above, females consistently differ in nest-site choice and construction and vary in how these aspects of investment shift across age (Delaney et al 2020a). These findings thus coincide and suggest that this population exhibits considerable individual variability in life-history strategies.…”

Exploration in red knots

“…While comparing repeatability can be useful for understanding the relative magnitude of variation, different variance components give different information on behaviour (Wilson, 2018). For example, within-individual variation reflects the individual consistency in behaviour and is likely to decrease during development as individuals gain different experiences (Delaney et al, 2020). Therefore, investigating factors affecting within-and among-individual variation as well as repeatability during development is helpful for understanding the mechanisms by which consistent differences arise (Dingemanse et al, 2022;Dochtermann and Royauté, 2019).…”