Seasonal and diel patterns in Pacific white‐sided dolphin (Lagenorhynchus obliquidens) pulsed calls near Barkley Canyon

Abstract

Evaluation of temporal patterns in offshore marine mammal activity through visual data collection can be impaired by light and weather conditions and the cost of ship time. The conditions‐independence and cost‐efficacy of acoustic data collection make it popular for researching the temporal patterns of wild dolphins. However, Pacific white‐sided dolphins (PWSDs) north of Southern California remain under‐researched. This study evaluates diel and seasonal patterns in PWSD communication signals detected in 480 days of near‐continuous passive acoustic data collected over 20 months from the Barkley Canyon node of Ocean Networks Canada's NEPTUNE observatory, offshore Vancouver Island, British Columbia, Canada. In this study, a random forest classifier is used to identify PWSD pulsed calls and false positives are manually removed. The resulting acoustic presence‐absence data set is evaluated for seasonal and diel patterns using generalized additive mixed models, considering masking effects from ambient noise. PWSDs are found to be vocally active during all diel periods year‐round, with high summer and low spring activity. Seasonally dependent diel patterns are identified, with PWSD pulsed calls exhibiting no diel pattern in spring, a slight increase in vocal activity during dusk and night in fall and winter, and a notable increase during night and dawn in summer.