"Playing the beat": Occurrence of Bio-duck calls in Santos Basin (Brazil) reveals a complex acoustic behaviour for the Antarctic minke whale (Balaenoptera bonaerensis).

The Antarctic minke whale (Balaenoptera bonaerensis) (AMW) is one of the smallest species among baleen whales, occurring in the southern hemisphere from Antarctica to near the equator, and performing seasonal migrations from polar to tropical waters. Information about (AMW) occurrence in the winter breeding grounds is scarce, mostly coming from old records from whaling stations before the 1960's international moratorium, such as Costinha Station in Northeastern Brazil (6° S / 34° W) and some sightings from few dedicated visual surveys. Acoustic methods can provide important data on the occurrence and distribution of migratory species. This work describes the occurrence of the Antarctic minke whale through acoustic detections of their "Bioduck" vocalisations in the Santos Basin, South-Southeastern Brazil (22° and 28° S / 42° and 48° W). Data was recorded between November 12 and December 19, 2015. AMW calls were detected for 12 days. We detected and classified 9 different Bio-duck calls in Brazilian coastal waters, evidencing a highly diverse acoustic behavior for the minke whale breeding ground. This is the first attempt to describe the acoustic diversity of AMW vocalizations in lower latitudes, contributing important information for future conservation efforts and management of AMW populations and their habitat. Therefore, our study presents the foremost acoustic evidence of the Antarctic minke whale in Brazilian coastal waters.

Whistles of the pantropical spotted dolphin (Stenella attenuata) in Santos Basin, western South Atlantic Ocean.

The vocal repertoire of the pantropical spotted dolphin (Stenella attenuata) is poorly documented, with no published information about acoustic signals from South Atlantic Ocean populations. We conducted passive acoustic monitoring and recording of S. attenuata population in the Santos Basin, Brazil, using a towed hydrophone array during line-transects surveys. Our monitoring yielded whistle samples derived from eight groups of S. attenuata, from which we selected 155 whistles for further analysis. Approximately 48% of the whistles presented ultrasonic frequency values, with maximum frequencies up to 31.1 kHz. Across the sample, the number of steps ranged from 0 to 20 and inflection points ranged from 0 to 8. On average, end frequencies were higher than start frequencies, and whistles generally presented wide frequency ranges, with an average of 11.3 kHz. The most predominant whistle contour category was "ascending-descending." Our study provides new information regarding the acoustic repertoire of this poorly documented species and will aid efforts for using acoustics to identify and monitor cetaceans in this region.