ORIGINAL ARTICLE
Repeatability and reproductive consequences of boldness in female
gray seals
Christine M. Bubac
1
&
David W. Coltman
1
&
W. Don Bowen
2,3
&
Damian C. Lidgard
3
&
Shelley L. C. Lang
2
&
Cornelia E. den Heyer
2
Received: 24 July 2017 /Revised: 12 May 2018 /Accepted: 23 May 2018 /Published online: 1 June 2018
#
Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract
Wild animals show consistent individual variation in behavior across time and/or contexts, now referred to as animal personality.
While this variability may have important ecological and evolutionary implications, how and why variation in animal personality
is maintained in a natural population remains unclear. In this study, we assessed the influence of environmental and biological
sources of variation on behavioral responses measured along the shy-bold continuum in a long-lived, iteroparous marine
mammal, the gray seal (Halichoerus grypus). Between 2008 and 2016, 469 females from the Sable Island, Nova Scotia breeding
colony of gray seals were given a boldness score in response to a human approach, designed to stimulate maternal defense of
offspring. Using generalized linear mixed-effects models (GLMM) in a Bayesian framework, we show that boldness is highly
repeatable between and within years. There were age differences in boldness, with younger females being less bold than older,
more experienced females providing some support for the life history trade-off hypothesis. We further used GLMMs to assess
sources of variation on offspring weaning mass. We found that young females that were bolder produced heavier pups than shyer
counterparts, and that pups produced by bolder females were on average ~ 2 kg heavier than pups of shy females. These results
provide further evidence that personality influences life history strategies, and illustrates the evolutionary potential of animal
personality in response to selection.
Significance statement
Consistent individual differences in behavior influence various aspects of ecology including species interactions, species distri-
butions, and life history strategies. However, how and why this individual variation is maintained in a natural population remains
uncertain. In this study, we assessed the influence of boldness, specifically maternal defense of offspring, on a component of
reproductive success in a long-lived marine mammal. We showed highly repeatable behavioral differences, and found that
boldness varied with age, with younger individuals being less bold than older individuals. Younger individuals that were bolder
produced heavier offspring than shyer counterparts. Our study contributes to an under-represented group of animals, wild marine
mammals, in the personality literature, and further prompts the investigation into the proximate and ultimate factors influencing
personality in an ecologically important marine predator.
Keywords Boldness
.
Animal personality
.
Life history
.
Gray
seal
.
Pinniped
.
Halichoerus grypus
Introduction
Understanding the origin and extent of biological variation in
natural populations is critical to the study of evolution.
Recently, considerable attention has been given to the evolu-
tionary and ecological implications of variation in animal per-
sonalities. Broadly defined as repeatable individual differ-
ences in behavioral responses over time or across different
contexts or both (Gosling 2001; Réale et al. 2007), animal
Communicated by L. Rendell
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00265-018-2515-5) contains supplementary
material, which is available to authorized users.
* Christine M. Bubac
bubac@ualberta.ca
1
Department of Biological Sciences, University of Alberta,
Edmonton, Alberta, Canada
2
Population Ecology Division, Bedford Institute of Oceanography,
Dartmouth, Nova Scotia, Canada
3
Biology Department, Dalhousie University, Halifax, Nova Scotia,
Canada
Behavioral Ecology and Sociobiology (2018) 72: 100
https://doi.org/10.1007/s00265-018-2515-5
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