Using spatio-temporal clustering to identify mortality patterns and anthropogenic drivers in the marine otter (Lontra felina) in north-central Chile

Abstract

Introduction Small marine carnivores inhabiting fragmented rocky coastlines are increasingly exposed to anthropogenic pressures, yet mortality drivers in these systems remain poorly quantified. Methods We analyzed 22 years of carcass records (2003–2024) and standardized necropsies to evaluate the contribution of anthropogenic causes and their spatial and temporal patterns in marine otters ( Lontra felina ) from north-central Chile. Results We documented 173 mortality events involving 181 individuals. Space–time permutation analyses revealed three significant peri-urban clusters associated with areas of high human activity. Among cases with assigned cause, anthropogenic drivers predominated, particularly free-ranging dog attacks, followed by fisheries bycatch and non-specific trauma. Although seasonal differences were not statistically significant, anthropogenic mortality contributed proportionally more during summer months. Discussion Our findings highlight terrestrial human-related pressures, particularly free-ranging dogs, as underrecognized mortality pathways in marine otters inhabiting human-dominated coastlines. Recurrent spatial clustering indicates predictable mortality risk hotspots and demonstrates the utility of spatio-temporal approaches for informing conservation and management strategies integrating terrestrial and marine systems.

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