My co-author and I are happy to announce the publication of two new papers of the acoustic ecology of gray whales.

Abstract: The gray whale (Eschrichtius robustus) is subject to elevated ambient noise in much of its range.Here we characterized the acoustic environment of a summer foraging bay, also used for nursing and weaning, on the west coast of Vancouver Island. This area is also subject to whale watching.We examined changes in whale call number, rate, and structure received on a passive acoustic monitoring system deployed in an altered acoustic landscape. In particular, increased anthropogenic noise was examined, using representative 1/3 octave frequency bands generated by whale watching vessels and float planes.Whale watching traffic significantly shaped the acoustic landscape of the foraging locale, with distinct diurnal patterns in ambient noise. Calling rate (calls/hour/individual) was unchanged relative to the ambient condition, yet the number of core calls heard in the recordings increased,and the number of motherese-type calls decreased with elevated ambient noise. Calls were generally lower in frequency and shorter in length in increased ambient noise conditions. This may represent a calling response or a masking effect from the noise additions. It shows, however, that calling between conspecifics could be affected by human-derived noise additions. Similar changes in received calls were seen in periods of increased wind and wave noise, although less so for abiotic natural, than anthropogenic noise. Changes in calling, or accuracy in call reception and interpretation, may negatively influence prey acquisition, conspecific communication, and reunion of cow-calf pairs.

Abstract: Passive acoustic monitoring adds to knowledge of whale presence and distribution over space and time. The gray whale (Eschrictius robustus) undertakes an annual migration between remote feeding and breeding locales, with its highly sonorous nature suggesting employment of low-frequency calls to be inherent to travel behaviours, perhaps aiding navigation and social cohesion. We consider whether these calling behaviours can be used to better understand the process of migration, where call presence and relative abundance might represent a means to track the progress of migrating whales. Passive acoustic recordings made on the west coast of Vancouver Island, a mid-way point of gray whale migration, were first analysed for abundance over time to examine the progression of migration. Then the acoustic record was compared to shore-based recordings undertaken from Point Vincente, California to better assess their use as a census tool. The timing in peaks of calling, particularly of far-ranging moan-like calls, and shore counts showed a high degree of congruence when considered with a lag time of 8 days to account for travel time between the two survey locations. This suggests that passive acoustic monitoring could complement the long running and shore-based counts in recording annual population movement, and add to our understanding of gray whales on poorly known segments of their migration route or at times when visual observations are not possible.