Abstract
Individuals vary in their stress-coping styles, characterized by specific behavioural and physiological traits that influence their response to stressors. Theory suggests that these traits are linked to underlying metabolic mechanisms that affect energy management strategies. Despite the potential of this powerful comparative approach, few studies have explored how stress-coping styles relate to energy management strategies. Using heart rate telemetry data from a large, capital-breeding pinniped, the grey seal (Halichoerus grypus), we sought to investigate the relationship that stress-coping styles (via individual resting heart rate variability, rHRV) may have on energy management strategies. Background energy expenditures, a proxy for metabolic rate and other background processes, and daily energy expenditures were found to be individually repeatable in grey seal mothers across successive breeding seasons. Proactive individuals (low rHRV) exhibited consistently higher background and daily energy expenditures than reactive females (high rHRV). However, reactive phenotypes were more variable overall in energy management strategy, highlighting greater flexibility in their energy management strategy. Our results highlight key energetic trade-offs associated with stress-coping styles in grey seal mothers during this short but critical life-history stage; proactive individuals tended to exhibit a single pattern of energy management, expending greater energy while incurring greater risk of over-spending, than those with a more reactive phenotype.