Remote acoustic monitoring of North Atlantic right whales (Eubalaena glacialis) reveals seasonal and diel variations in acoustic behavior.

Remote acoustic monitoring is a non-invasive tool that can be used to study the distribution, behavior, and habitat use of sound-producing species. The North Atlantic right whale (Eubalaena glacialis) is an endangered baleen whale species that produces a variety of stereotyped acoustic signals. One of these signals, the "gunshot" sound, has only been recorded from adult male North Atlantic right whales and is thought to function for reproduction, either as reproductive advertisement for females or as an agonistic signal toward other males. This study uses remote acoustic monitoring to analyze the presence of gunshots over a two-year period at two sites on the Scotian Shelf to determine if there is evidence that North Atlantic right whales may use these locations for breeding activities. Seasonal analyses at both locations indicate that gunshot sound production is highly seasonal, with an increase in the autumn. One site, Roseway West, had significantly more gunshot sounds overall and exhibited a clear diel trend in production of these signals at night. The other site, Emerald South, also showed a seasonal increase in gunshot production during the autumn, but did not show any significant diel trend. This difference in gunshot signal production at the two sites indicates variation either in the number or the behavior of whales at each location. The timing of the observed seasonal increase in gunshot sound production is consistent with the current understanding of the right whale breeding season, and our results demonstrate that detection of gunshots with remote acoustic monitoring can be a reliable way to track shifts in distribution and changes in acoustic behavior including possible mating activities

Remote acoustic monitoring of North Atlantic right whales (Eubalaena glacialis) reveals seasonal and diel variations in acoustic behavior.

Remote acoustic monitoring is a non-invasive tool that can be used to study the distribution, behavior, and habitat use of sound-producing species. The North Atlantic right whale (Eubalaena glacialis) is an endangered baleen whale species that produces a variety of stereotyped acoustic signals. One of these signals, the "gunshot" sound, has only been recorded from adult male North Atlantic right whales and is thought to function for reproduction, either as reproductive advertisement for females or as an agonistic signal toward other males. This study uses remote acoustic monitoring to analyze the presence of gunshots over a two-year period at two sites on the Scotian Shelf to determine if there is evidence that North Atlantic right whales may use these locations for breeding activities. Seasonal analyses at both locations indicate that gunshot sound production is highly seasonal, with an increase in the autumn. One site, Roseway West, had significantly more gunshot sounds overall and exhibited a clear diel trend in production of these signals at night. The other site, Emerald South, also showed a seasonal increase in gunshot production during the autumn, but did not show any significant diel trend. This difference in gunshot signal production at the two sites indicates variation either in the number or the behavior of whales at each location. The timing of the observed seasonal increase in gunshot sound production is consistent with the current understanding of the right whale breeding season, and our results demonstrate that detection of gunshots with remote acoustic monitoring can be a reliable way to track shifts in distribution and changes in acoustic behavior including possible mating activities

ANOVA results for the seasonality analysis of both sites.

<p>ANOVA results for the seasonality analysis of both sites.</p

Seasonal trends of gunshot signal production.

<p>The hours per day with gunshots (GS) showed a seasonal pattern in both Roseway West (top) and Emerald South (bottom). In Roseway West, August-November had significantly more gunshot presence than other months. Emerald South, despite having fewer hours per day with gunshots overall, still exhibits a seasonal trend, with significantly more gunshot hours during the second half of the year.</p

Calls of North Atlantic right whales Eubalaena glacialis contain information on individual identity and age class

Passive acoustic monitoring is a powerful tool that allows remote detection of marine mammals through their vocalizations. While call detection provides information on species presence, additional information may be contained within the vocalizations that could provide more information regarding the demographics and/or number of individuals in a particular area based on passive acoustic detections. The North Atlantic right whale Eubalaena glacialis produces a stereotyped upswept call, termed the upcall, that is thought to function as a long-distance contact call in this species. As such, the call is likely to contain cues providing information about the individual producing it. The goal of this study was to test whether the right whale upcall could potentially encode information related to the identity and age of the caller. Using upcalls recorded from 14 known individuals through non-invasive suction cup archival acoustic tags, we demonstrate that the upcall does contain sufficient information to discriminate individual identity and age class, with average classification levels of 72.6 and 86.1%, respectively. Parameters measured from the fundamental frequency, duration, and formant structure were most important for discrimination among individuals. This study is the first step in demonstrating the feasibility of obtaining additional data from passive acoustic monitoring to aid in the conservation efforts for this highly endangered species

Locations of autonomous recording units on the Scotian Shelf.

<p>Roseway West: 42°58′00″ N 65°03′24″W; Emerald South: 43°8′54″N 62°45′42″W. Numbers correspond to water depth in meters.</p

Average and standard deviation of gunshot rates for the light regimes in both sites.

<p>Average and standard deviation of gunshot rates for the light regimes in both sites.</p

Average and standard deviation of hours per day of gunshot activity for each site.

<p>Average and standard deviation of hours per day of gunshot activity for each site.</p

Spectrogram of a gunshot sound recorded in Roseway West.

<p>Spectrogram parameters: 2 kHz sampling, Hann window, discrete Fourier transform (DFT) size 128, analysis resolution  = 15.6 Hz and 0.032 s, 50% overlap.</p