  We provide quantitative evidence suggesting social learning in sperm whales
across socio-cultural boundaries, using acoustic data from the Pacific and
Atlantic Oceans. Traditionally, sperm whale populations are categorized into
clans based on their vocal repertoire: the rhythmically patterned click
sequences (codas) that they use. Among these codas, identity codas function as
symbolic markers for each clan, accounting for 35-60% of codas they produce. We
introduce a computational method to model whale speech, which encodes rhythmic
micro-variations within codas, capturing their vocal style. We find that vocal
style-clans closely align with repertoire-clans. However, contrary to vocal
repertoire, we show that sympatry increases vocal style similarity between
clans for non-identity codas, i.e. most codas, suggesting social learning
across cultural boundaries. More broadly, this subcoda structure model offers a
framework for comparing communication systems in other species, with potential
implications for deeper understanding of vocal and cultural transmission within
animal societies.
