Abstract

The spotted salamander (Ambystoma maculatum) is a pool-breeding species thought to depend on small mammal burrows for survival in terrestrial habitats. We investigated burrow occupancy patterns using laboratory and field experiments where salamanders were housed alone or in pairs, in arenas with either one or two burrows. In the single-burrow field experiment, intruders were significantly less likely than residents to occupy burrows, and the probability of burrow occupancy declined following nighttime rain. However, spotted salamanders frequently co-occupied burrows (mean burrow co-occupancy rate, 59%). In the single-burrow laboratory experiment, mean burrow occupancy rate was 98%, both when salamanders were housed alone and in pairs. However, salamanders housed in pairs with two burrows co-occupied burrows less frequently than expected by chance, and greater size disparity was associated with lower burrow co-occupancy rates. Our results suggest that spotted salamanders may often fail to effectively defend burrows and exclude conspecifics, although avoidance of occupied burrows could, in some contexts, affect spacing in terrestrial habitats.