Behavioral dominance and its relationship to habitat patch utilization by the hispid cotton rat (Sigmodon hispidus)



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Patterns of habitat patch occupancy by cotton rats (Sigmodon hispidus) had indicated in previous studies that spacing behavior might be an important factor in population regulation of this species. In order to test this, two experimental patchy habitats were created composed of alternating 0.2-ha squares with overhead shrub cover (possible predator protection) present (preferred habitat) and with shrub cover absent (removed by mowing). It was hypothesized that subordinate animals would occupy less preferred patches, thus exhibiting reduced fitness (survival and reproduction). Habitat selection experiments in enclosures indicated that cotton rats preferred patches with shrubs present. However, this preference was density-dependent with more equal habitat occurrence at higher densities. Animals captured in patches with shrubs present were larger, moved greater distances, and were in reproductive condition more often than animals in patches with shrubs removed. There was no difference in survival rates between patch types, however. Paired behavioral encounters between animals captured in the two patch types resulted in animals from patches with shrubs present exhibiting significantly more dominance-type behavior and winning encounters significantly more often than those from patches with shrubs absent. Results suggested that spacing behavior is probably important in regulating habitat occurrence of cotton rats. Dominant animals were able to occupy preferred habitat patches. There was no survival difference between patch types indicating that dominance was not important in population regulation in this study. Unpreferred habitat was still able to support cotton rats without significantly decreased survival rates.



Hispid cotton rat