Analyzing whale calling through Hawkes process modeling

TL;DR

This paper models North Atlantic right whale calling behavior using Hawkes processes, revealing how calls are influenced by time, space, and ambient noise, with implications for understanding whale communication and conservation.

Contribution

It introduces a novel spatiotemporal Hawkes process model for whale calls, integrating diel patterns and ambient noise effects, to analyze whale communication dynamics.

Findings

Calls are spatially and temporally clustered.

Whales call more during twilight hours.

Ambient noise suppresses whale calling activity.

Abstract

Sound is assumed to be the primary modality of communication among marine mammal species. Analyzing acoustic recordings helps to understand the function of the acoustic signals as well as the possible impact of anthropogenic noise on acoustic behavior. Motivated by a dataset from a network of hydrophones in Cape Cod Bay, Massachusetts, utilizing automatically detected calls in recordings, we study the communication process of the endangered North Atlantic right whale. For right whales an "up-call" is known as a contact call, and ensuing counter-calling between individuals is presumed to facilitate group cohesion. We present novel spatiotemporal excitement modeling consisting of a background process and a counter-call process. The background process intensity incorporates the influences of diel patterns and ambient noise on occurrence. The counter-call intensity captures potential excitement, that calling elicits calling behavior. Call incidence is found to be clustered in space and time; a call seems to excite more calls nearer to it in time and space. We find evidence that whales make more calls during twilight hours, respond to other whales nearby, and are likely to remain quiet in the presence of increased ambient noise.