Cetacean strandings (CS) have been reported in increasing numbers in coastal areas worldwide. Although the causes of these strandings are unknown, a number of anthropogenic and environmental factors have been suggested. This paper aims to characterize CS patterns and describe their finescale spatiotemporal dynamics. We analysed spatial and spatiotemporal CS patterns in Chile from January 1968 to January 2020. We identified a total of 436 CS events affecting eight cetacean families, 21 genera, and 35 species, which represent more than 85% of the reported species richness for the country. Most CS events (94.1%) were single (i.e., ≤two individuals). There were also 18 mass stranding (three to 24 individuals, 4.1%) and nine unusually large mass stranding events (>25 individuals, 2%). Purely spatial tests showed CS events appearing in random occurrence along the Chilean coast. Local tests for spatio-temporal clusters, however, identified a greater number of hotspots reported in the southernmost part of the country, namely, Chilean Patagonia. Specifically, significant spatio-temporal clusters were identified and defined as containing three or more individuals within a two-month period as a focal coastal event (<1 km radius). It is a cause of concern that CS events in Chile have been increasing consistently over the last decades, and although we were not able to identify their causes, we are able to highlight the importance of changes in climate conditions and of an increase in monitoring activities as primary drivers for such patterns, particularly important in Chilean Patagonia. Marine mammals are prime sentinel species for ecosystems and human health alike 1. Many of them have long life spans, are long-term coastal residents, feed at a high trophic level, and have unique fat stores that can serve as depots for anthropogenic toxins 1. Consequently, the study of stranded marine mammals provides valuable records of circulating pathogens and contaminants that could be a risk for coastal populations and provide important information in regard to marine mammals' biodiversity in coastal areas worldwide 2-4. Likewise, stranding records and associated attributes 5 can provide vital information on species richness and diversity by identifying spatial locations and periods of occurrence 6 , and they can also provide a very effective early warning system for the protection of human health 1. Cetacean strandings (CS) constitute a worldwide phenomenon, yet the cause of these events remains largely unknown 7. Although few primary causes have been proposed, there is a general agreement that CS are multifactorial in nature and species dependent 6. For instance, proposed causes include navigational errors from bathymetric features, coastal configuration; or geomagnetic topography 8,9 ; climate or oceanographic events 10,11 ; anthropogenic noise and sonar interference 12,13 ; pollution 14,15 ; infectious diseases 16-18 , and behavioural patterns 19 .
