This work aims to analyze the use of shelters by Lontra longicaudis, through microsatellite analysis. DNA extraction is performed according to the silica-guanidine methodology. Qui-square test (χ²) is applied to check sample differences. The similarity of genotypes in the shelters is calculated using the Morisita Index of Similarity and the Jaccard Community Coefficient. Two shelters exhibited high similarities. These preliminary results suggest that the size of the otter population is, at least six individuals, and different otters can use the same shelters.