Abstract
Differences in both stable and labile state variables are known to affect the emergence and maintenance of consistent interindividual behavioral variation (animal personality or behavioral syndrome), especially when experienced early in life. Variation in environmental conditions experienced by gestating mothers (viz. nongenetic maternal effects) is known to have significant impact on offspring condition and behavior; yet, their effect on behavioral consistency is not clear. Here, by applying an orthogonal experimental design, we aimed to study whether increased vitamin D3 content in maternal diet during gestation (vitamin‐supplemented vs. vitamin control treatments) combined with corticosterone treatment (corticosterone‐treated vs. corticosterone control treatments) applied on freshly hatched juveniles had an effect on individual state and behavioral consistency of juvenile Carpetan rock lizards (Iberolacerta cyreni). We tested the effect of our treatments on (a) climbing speed and the following levels of behavioral variation, (b) strength of animal personality (behavioral repeatability), (c) behavioral type (individual mean behavior), and (d) behavioral predictability (within‐individual behavioral variation unrelated to environmental change). We found higher locomotor performance of juveniles from the vitamin‐supplemented group (42.4% increase), irrespective of corticosterone treatment. While activity personality was present in all treatments, shelter use personality was present only in the vitamin‐supplemented × corticosterone‐treated treatment and risk‐taking personality was present in corticosterone control treatments. Contrary to our expectations, behavioral type was not affected by our treatments, indicating that individual quality can affect behavioral strategies without affecting group‐level mean behavior. Behavioral predictability decreased in individuals with low climbing speed, which could be interpreted as a form of antipredator strategy. Our results clearly demonstrate that maternal diet and corticosterone treatment have the potential to induce or hamper between‐individual variation in different components of boldness, often in interactions.
Highlights
In the first linear mixed models (LMMs), we used snout-vent length (SVL) as response variable, while maternal vitamin supplementation, corticosterone treatment, and their interaction were added as fixed factors
Maternal diet affected offspring climbing speed positively; we found significant treatment effects on different levels of juveniles' behavioral consistency, suggesting that individual quality can modify the effect of corticosterone in “switching” individual behavioral variation on/off
Corticosterone treatment did not affect offspring climbing speed; we found a clear effect of maternal vitamin treatment: Juveniles from vitamin D3 supplemented mothers had higher climbing speed (42.4% increase) than conspecifics from control mothers
Summary
We noosed 17 gravid females between 20 May and 21 June 2016 at the Puerto de Navacerrada (Sierra de Guadarrama Mts., Community of Madrid, Spain, 1,900 m asl, approximately). In the third model, climbing speed was our response variable, the treatments and their interaction were added as fixed factors and both SVL and BW were included as covariates to control for the effect of size and condition. We ran LMMs on the behaviors separately to test whether treatments affected behavioral type In these models, the different behavioral traits were our response variables, treatments and their interactions were added as fixed effects, while mother identity and individual were random factors. We added z-transformed order of trials (hereafter: time) both as a single fixed effect and as a random slope (i.e., in interaction with individual) to the models to test for habituation on the group and individual levels directly. All analyses were performed using the R statistical environment (R Developmental Core Team, 2018)
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