The study of the spatial distribution of individuals in a wild population provides information on the factors influencing their habitat selection, which is of fundamental importance because of its potential consequences for survival and reproduction. This importance is even greater when a species exploits a specific site over a long period of time (e.g. nests, dens or burrows). For species that do not build such sites from scratch, but rather preemptively occupy already available ones, theory predicts that optimal sites will be occupied first and that individuals will rearrange their distribution by changing site, if this should results in higher fitness, for instance when a resident disperses or dies, or when environmental changes occur. As a result, individual-dependent and context-dependent variations in habitat selection within a population are generally observed. Here, we used occupancy data of burrows from 2012 to 2019 in a population of a small diurnal rodent, the Eastern chipmunk (Tamias striatus) in southern Québec, Canada, to assess burrow-site selection in this species. We first compared characteristics of the burrow surroundings (microhabitat) with those of equivalent unused plots. Then, we tested if microhabitat characteristics and the phenotype of successive/long-lasting resident(s) could explain burrow occupancy over time.
Results/Conclusions
On our study site since 2012, we found 229 distinct burrows, that were occupied by 311 chipmunks at different times. Overall, 16 % of chipmunks successively inhabited more than one burrow and 41% of burrows were occupied more than once by different individuals. Our analyses revealed that chipmunks select microsites with a higher abundance of woody debris and a greater slope for burrow locations compared to microsites without burrows. These characteristics could, respectively, promote predator avoidance by providing refuges and the opportunity to shelter more quickly and quietly in burrows, and allow for better drainage and isolation of burrows. Preliminary results further indicate that occupancy of a given burrow increases with the proportion of adults (compared to juveniles) that previously lived in it and decreases with its microhabitat canopy height. Low canopy height can reduce prey detection by chipmunks’ aerial predators. This suggests that adults may be able to make better choices than juveniles when searching for a suitable burrow. Taken together, our results improve our comprehension of habitat selection mechanisms and emphasize the importance of taking individual differences into account in such studies.