Vocal behavior of blue whales () in the Gulf of Corcovado, Chile, was analysed using both audio and accelerometer data from digital acoustic recording tags (DTAGs). Over the course of three austral summers (2014, 2015 and 2016), seventeen tags were deployed, yielding 124 h of data. We report the occurrence of Southeast Pacific type 2 (SEP2) calls, which exhibit peak frequencies, durations and timing consistent with previous recordings made using towed and moored hydrophones. We also describe tonal downswept (D) calls, which have not been previously described for this population. As being able to accurately assign vocalizations to individual whales is fundamental for studying communication and for estimating population densities from call rates, we further examine the feasibility of using high-resolution DTAG accelerometers to identify low-frequency calls produced by tagged blue whales. We cross-correlated acoustic signals with simultaneous tri-axial accelerometer readings in order to analyse the phase match as well as the amplitude of accelerometer signals associated with low-frequency calls, which provides a quantitative method of determining if a call is associated with a detectable acceleration signal. Our results suggest that vocalizations from nearby individuals are also capable of registering accelerometer signals in the tagged whale's DTAG record. We cross-correlate acceleration vectors between calls to explore the possibility of using signature acceleration patterns associated with sounds produced within the tagged whale as a new method of identifying which accelerometer-detectable calls originate from the tagged animal.

A joint effort between WHOI and the Melimoyu Ecosystem Research Institute (MERI) sought to gain a better understanding of a population of blue whales (Balaenoptera musculus) in the Gulf of Corcovado, Chile. A cruise in March 2014 resulted in the deployment of 5 DTAGs, which are miniature sound and orientation recording tags that are attached via suction cups. A total of five tag deployments on four individual whales were achieved, totaling 21 hr 11 min. Dives were predominantly between 10 and 50 m in depth, with a maximum of 139 m. Sloughed skin found on the suction cups of recovered tags and fecal samples were preserved to be used for genetic, dietary and pollutant analyses. Acoustic data on the tags revealed numerous calls from distant blue whales, and an apparent call exchange was recorded between a tagged juvenile whale and a distant animal. Photo-identification images and acoustic recordings of all marine mammal species encountered were obtained whenever possible; these included humpback whales (Megaptera novaeangliae), Peale's dolphins (Lagenorhynchus australis), Chilean dolphins (Cephalorhynchus eutropia), and bottlenose dolphins (Tursiops truncatus). Continuation of this collaboration has great potential to provide information to policy makers regarding how to protect the unique habitats in this region.

Vocal behavior of blue whales (Balaenoptera musculus) in the Gulf of Corcovado, Chile, was analyzed using digital acoustic recording tags (DTAGs). We report the occurrence of Southeast Pacific type 2 (SEP2) calls, which exhibit peak frequencies, durations, and timing consistent with previous reports. We also offer the first description of tonal downswept (D) calls for this population. Since being able to accurately assign vocalizations to individual whales is fundamental for studying communication and for estimating population densities from call rates, we further examine the feasibility of using DTAG accelerometers to identify low-frequency calls produced by tagged whales. We cross-correlated acoustic signals with simultaneous tri-axial accelerometer readings in order to analyze the phase match as well as the amplitude of accelerometer signals associated with low-frequency calls, which provides a reliable method of determining if a call is associated with a detectable acceleration. Our results suggest that vocalizations from nearby individuals are also capable of registering accelerations in the tagged whale’s DTAG record. We cross-correlate acceleration vectors between calls to explore the possibility of using signature acceleration patterns associated with sounds produced within the tagged whale as a new method of identifying which accelerometer-detectable calls originate from the tagged animal.

Eastern South Pacific southern right whales (ESPSRW) are a subpopulation of southern right whales (Eubalaena australis) off the coasts of Peru and Chile recognized by the International Union for the Conservation of Nature (IUCN) as critically endangered as a result of heavy whaling efforts in the late 18th to 20th centuries. Most recent population estimates put their numbers around 50 individuals. To test for the efficacy of passive acoustic monitoring of this population, we recorded 5 months of continuous acoustic data (January 2012-June 2012) off the southwestern tip of Isla de Chiloé. To test for trends in occurrence, we identified 11,313 individual ESPSRW upsweep calls, which have been associated with maintaining contact with conspecifics. Call occurrence increased over the course of the deployment and peaked between April and June, indicating an increase in use of this area. A clear diel pattern in which upsweep calls were predominately detected during dusk and night hours was identified, indicating ESPSRW are likely foraging during daylight hours, as upsweep calls are inversely related to foraging behavior. We quantified noise levels in the frequency range of their communication (100 Hz third octave) to understand the change in active space whales may be experiencing. We measured noise levels from 90 dB re 1 μPa to 111 dB re 1 µPa (5th and 95th percentile), a 21 dB fluctuation that results in an order-of-magnitude decrease in active space area. We identified sources of high noise at or above the 75th percentile as predominately blue whale calls (occurring in 71.6% of total sampled minutes) and ship noise (occurring in 69.4% of total sampled minutes). Ship noise was responsible for outliers in excess of 140 dB re 1 µPa. In a population as diminished as ESPSRW, such disruptions of their communication range could result in significant barriers to maintaining contact with conspecifics. Passive acoustic monitoring is a powerful tool for monitoring populations as rarely sighted as ESPSRW. Understanding trends in presence and behavior as well as potential sources of disruption to their calling behavior is vital to determining conservation measures that will be most effective toward helping this critically endangered population.