COS 77-2 - Stability in a small mammal community over 70 years

Background/Question/Methods

Understanding how community assemblages respond to climate change is essential for predicting ecosystem changes and mitigating potential biodiversity loss. Climate change may influence community composition by affecting populations directly or indirectly, and long-term studies are uniquely poised to untangle the relative influences of these types of factors. We used 70 years of trapping data from the Algonquin Small Mammal Project to examine how climate variability, changes in food availability, and density dependence have affected small mammal population abundances and community composition.

Results/Conclusions

Using multivariate autoregressive state space models, we detected two underlying shared trends in small mammal population dynamics, suggesting trophic linkages among the species. We found that the Algonquin Park small mammal community exhibited relative population stability over time, responding quickly to perturbations in abundances, as evidenced by high return rates and low reactivity metrics. However, the degree of density dependence differed among species, with deer mice (Peromyscus maniculatus) exhibiting the greatest negative feedback, and woodland jumping mice (Napaeozapus insignis) the least. Changes in small mammal abundances were best explained by seed availability and the lag effects of seed availability, while environmental factors were less important. However, higher maximum summer temperatures negatively affected small mammal abundances the following year. Small mammal community composition varied through time, with evenness increasing in later years, as deer mice declined, and other species increased. We conclude that endogenous (i.e., density dependence) and indirect (i.e., food availability) factors largely drive changes in the Algonquin Park small mammal community, with climate change having less influence. Despite the stability of this community over the past seven decades, a warmer and less predictable future climate may affect seed availability and therefore the dynamics of these populations.