Assessment of the relative abundance and habitat of Neotropical Otter Lontra annectens (Carnivora: Mustelidae) in Durango, Mexico

Introduction: Neotropical otter (Lontra annectens) is a widespread aquatic mammal in Mexico. Unfortunately, anthropogenic activities in Mexico have modified and polluted the habitat of this otter species, which has been listed as threatened. In Durango State, Neotropical otters thrive in preserved areas within the Sierra Madre Occidental. However, there are few scientific reports of their presence at the San Diego River. Objective: To evaluate the habitat and compare the relative otter abundance over a 10 km section of the San Diego River using two widely used methods. Methods: The habitat was characterized by measuring the river's physical structures, water physicochemical analyses, and plant species identification by strata and cover. Otter abundance was estimated by counting scats and latrines over 15 months. Data were analyzed with a stepwise regression to obtain the habitat variables significantly correlated with otter abundance. Results: Vegetation was composed of a gallery forest with low deciduous forest associations. The highest plant cover corresponded to the herbaceous stratum (50.87 %), followed by the tree stratum (30.4 %) and the shrub stratum (18.71 %) and the species Salix bomplandiana, Baccharis salicifolia, Sanvitalia ocymoides, and Muhlenbergia montana had the highest Importance Value Index (IVI). Otter abundance was 0.50 ± 0.14 otters km-1 using Method 1 ( ) and 1.12 ± 0.30 otters’ km-1 using Method 2 (E), with significant differences between them. Conclusion: A model was constructed to predict the number of scats (SC) about otter abundance; the significant habitat variables were smaller rock diameter (SRD), a greater distance to the shoreline (DSL), turbidity (TB), and pH.