Movement Strategies of Cetaceans in an Oceanic Island Environment

Speaker: Dr. Marc Fernandez Morron
Researcher, MARE Madeira

Large marine predators, such as cetaceans, occupy an apex position within marine food webs, playing a vital role in regulating biodiversity and facilitating the transfer of energy and nutrients across ocean basins. Their horizontal and vertical movements connect disparate marine regions and significantly influence trophic interactions. However, the distribution of critical habitat patches is often influenced by oceanographic processes. Consequently, environmental changes and increasing anthropogenic pressures can affect cetacean use of space in ways that undermine ecosystem functioning and existing conservation measures. Robust inference thus necessitates integrative approaches that combine long-term observations (such as photo-identification) with biotelemetry and movement models. These methodologies allow the investigation of behavior across multiple scales, facilitating the identification of residency areas and exploratory excursions. Here, we present telemetry data from 26 individuals tagged off Madeira Island, specifically focusing on short-finned pilot whales, rough-toothed dolphins, false killer whales, and sperm whales. We aim to describe the broad-scale movements of these species across the Macaronesia region (encompassing the Azores, Madeira, and the Canary Islands), using the pilot whale as a case study for condition-dependent movement tactics around oceanic islands. Telemetry data collected from pilot whales between 2018 and 2024 revealed extensive ranging across the eastern North Atlantic, while also identifying behaviors associated with island habitats, characterized by area-restricted movements and long residency phases around Madeira. Linking behavioural state estimates with oceanographic conditions clarifies how oceanic islands can structure partial migration and residency strategies and identifies predictable near-island habitats that may warrant targeted, adaptive management.