Movements and Distribution of Short-finned Pilot Whales Off Ecuador as Revealed by Sighting and Satellite Tagging Data

Short-finned pilot whales were recorded and satellite-tagged during pelagic monitoring along the central coast of Ecuador (1º15′ S – 2º30′ S) to improve understanding of the ecology and demography of this pelagic cetacean. Survey effort comprised 18 trips (seven in 2024 and 11 in 2025), totaling 2,587.2 km and 90.1 hours, with greater coverage during the warmer season (February-April). Thirteen groups were documented, totaling an estimated 218–250 individuals in water ranging from 240 to 1,771 m in depth. Relative abundance along the continental slope was 9.04 whales per 100 km of survey effort. Mean group size was 18.1 individuals (SD = 9.86; range = 2–35). A total of 139 distinct individuals were photo-identified, including eight intra-annual resightings. Satellite tags were deployed on twelve individuals. Based on spatial distribution, tagged individuals were classified into two clusters: coastal and oceanic. The 95% utilization distribution (UD) of the coastal cluster encompassed 28,353 km² and was primarily associated with the continental slope. In contrast, the oceanic cluster exhibited a substantially larger 95% UD (457,000 km²), extending across deep-slope and offshore waters. This bathymetrically structured spatial segregation suggests the presence of two ecotypes with distinct habitat-use strategies. Offshore movements further suggest that the Carnegie Ridge may function as a migratory pathway between mainland Ecuador and the Galapagos Islands. We recommend expanding surveys to the colder and dry season to better resolve population structure and assess relationships between pilot whale distribution and environmental variability.