Environmental change and long-term body mass declines in an alpine mammal

Introduction: Climate and environmental change have driven widespread changes in body size, particularly
declines, across a range of taxonomic groups in recent decades. Size declines could substantially impact on the
functioning of ecosystems. To date, most studies suggest that temporal trends in size have resulted indirectly from
climate change modifying resource availability and quality, affecting the ability of individuals to acquire resources
and grow.
Results: Here, we investigate striking long-term body mass declines in juvenile Alpine chamois (Rupicapra rupicapra),
within three neighbouring populations in the Italian Alps. We find strong evidence that increasing population density
and warming temperatures during spring and summer are linked to the mass declines. We find no evidence that the
timing or productivity of resources have been altered during this period.
Conclusions: We conclude that it is unlikely that environmental change has driven body size change indirectly via
effects on resource productivity or phenology. Instead, we propose that environmental change has limited the ability
of individuals to acquire resources. This could be due to increases in the intensity of competition and decreases in time
spent foraging, owing to high temperatures. Our findings add weight to a growing body of evidence for long-term
body size reductions and provide considerable insight into the potential drivers of such trends. Furthermore, we
highlight the potential for appropriate management, for instance increases in harvest size, to counteract the impacts of
climate change on body mass.