Data from: Glucocorticoids negatively relate to body mass on the short-term in a free-ranging ungulate

Environmental fluctuations force animals to adjust glucocorticoids (GCs)
secretion and release to current conditions. GCs are a widely used proxy
of an individual stress level. While short-term elevation in GCs is
arguably beneficial for fitness components, previous studies have
documented that the relationship between long-term baseline GCs elevation
and fitness components can vary according to ecological and individual
factors and according to the life-history of the species studied. Using
longitudinal data on roe deer (Capreolus capreolus) from two populations
facing markedly different environmental contexts, we tested whether
baseline GC levels negatively correlate with body mass – a trait
positively associated with demographic individual performance – on the
short- to long-term. In support, higher baseline GC concentrations were
associated to lighter body mass, both measured during the same capture
event, in adults of both populations. Overall, we showed that despite the
marked environmental and demographic differences between populations and
despite the between-sex differences in life history (i.e. reproductive
tactics), the relationship between body mass and GCs is consistent across
environmental contexts, but might differ according to the life history
stage of an individual. This work opens promising perspectives to further
explore the relationship between GC and fitness-related traits according
to life history stages in free-ranging mammals across seasonal and
environmental contexts. The timing and context-dependence of GC levels
highlight the complexity of studying stress responses in the wild.