Predicting mesoscale movement of sperm whale units in the Caribbean based on social dynamics

Sperm whales (Physeter macrocephalus) navigate complex oceanic environments and social structures. In the waters off Dominica, female and juvenile whales form long-lasting social units and vocal clans, distinguished by unique click dialects known as codas. While prey availability is often seen as a driver of whale movements, we highlight the role of sociality in shaping spatial behavior. Using 20 years of photo-identification data, we examined the sequential presence of social units for predictable patterns linked to social structure. Applying long short-term memory (LSTM) neural networks to sequences of one to five days across 16 states including 14 units, mature males and unknown units, we achieved prediction accuracies over 60%, far exceeding random chance (0.00001526). We then compared unit-to-unit transition probabilities to their social association matrix using a Hemelrijk test, revealing strong alignment between movement and social bonds for some of the units. To support long-term monitoring, we developed an acoustic classification method based on inter-pulse intervals (IPIs) in echolocation clicks, serving as acoustic fingerprints linked to body size. Kernel Density Estimation (KDE) classified units with 78.26% accuracy. Our findings provide quantitative evidence that sperm whale movements are socially coordinated and predictable, offering new insights into the spatial and social dynamics of sperm whale societies and highlighting the role of social affiliation in shaping large-scale movement patterns.