Acoustic analysis of complex contact calls confirms social structuring in St. Lawrence belugas

Jaclyn Aubin, Marie-Ana Mikus, Robert Michaud, Daniel Mennill, Valeria Vergara

Photo-identification surveys of the St. Lawrence beluga population conducted since 1989 reveal a highly aggregated distribution with a clear sexual segregation and spatial segregation of all-male and female-and-young herds. These surveys also suggest socio-spatial structuring with individuals sharing preferred areas. 
Belugas are thought to use individual or familial vocal signatures, known as complex contact calls. Complex contact calls can be classified into “types” that are believed to be primarily used by specific individuals or groups. Therefore, belugas may be distinctive acoustically, making acoustic monitoring of complex contact calls a promising tool for monitoring the distribution of belugas. 
We used over 2,200 hours of acoustic recordings from 3 recording areas distributed across the St. Lawrence to identify complex contact calls and to test the hypothesis that St. Lawrence belugas live in distinct summer communities. 
We hypothesized that, if St. Lawrence belugas belong to unique social communities, then each contact call type would be primarily recorded in a single area.
Preliminary results support our hypothesis: of 169 contact call types identified, 86% were identified in a single area. Only 8 contact call types (5%) were recorded in all three areas. The presence of unique beluga communities that preferentially use certain areas of the Estuary has important conservation implications. This population is managed as a single, well-mixed unit, and the presence of unique communities could dramatically alter how this population is managed, particularly with respect to its critical habitats. However, the repertoire discovery curves for two areas suggest that many contact call types have yet to be identified. Therefore, much work is still needed to confirm the presence of beluga communities in the St. Lawrence.