Whistle source levels of free-ranging bottlenose dolphins and Atlantic spotted dolphins in the Gulf of Mexico

Abstract

Whistles of bottlenose dolphins (Tursiops truncatus) and Atlantic spotted dolphins (Stenella frontalis) in the eastern Gulf of Mexico were recorded and measured with a calibrated towed hydrophone array. Surveys encountered groups of both bottlenose (N = 10) and spotted dolphins (N = 5). Analysis of those data produced 1695 bottlenose dolphin whistles and 1273 spotted dolphin whistles with a high signal-to-noise ratio. Whistle frequency metrics were lower in bottlenose than spotted dolphins, while whistle duration was longer in spotted dolphins, data that may help inform automatic classification algorithms. Source levels were estimated by determining the range and bearing of an individual dolphin from the array and then adding the predicted transmission loss to the calculated received level. The median bottlenose dolphin source level was 138 dB re 1μPa at 1 m with a range of 114-163 dB re 1μPa at 1 m. The median spotted dolphin source level was 138 dB re 1μPa at 1 m with a range of 115-163 dB re 1μPa at 1 m. These source level measurements, in conjunction with estimates of vocalization rates and transmission loss models, can be used to improve passive acoustically determined dolphin abundance estimates in the Gulf of Mexico.

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…Common bottlenose dolphins inhabit tropical to temperate waters globally and occur around Australia in coastal as well as offshore waters [147,272]. Bottlenose dolphins have been acousti- [501] cally recorded in QLD, Australia [284], New Zealand [285], the Eastern Tropical Pacific [151,152], Hawaii [230], California [276,286], the Gulf of Mexico [163,253,276,287], the Caribbean [288], Central America [286,289], Brazil [270,290], Uruguay [291], Argentina [276], Namibia [292], the Northwest Atlantic [163,174], the Northeast Atlantic [282,293,294], Scotland and the UK [282,295,296], Mediterranean [156,293,[297][298][299], and Portugal [300]. Many recordings have also been taken of bottlenose dolphins in captivity (e.g.…”

“…Much of the literature focuses on whistles and geographic differences [151,152,156,163,174,253,270,276,286,[289][290][291][292][293][295][296][297][298]300,302]. Biphonic whistles have been reported [299].…”

Whistle source levels of free-ranging beluga whales in Saguenay-St. Lawrence marine park

“…Minimum, maximum, median, and mean whistle SLs are similar to those of white beaked dolphins, 18 killer whales, 16 bottlenose, and spotted dolphins. 19 …”

Overlapping use of an artificial reef by humans and an apex predator (Tursiops truncatus) in the New York Bight

“…, Buckstaff , Hildebrand , Frankel et al . ). We selected sounds that were barely detectable to the listener (signal to noise ratio ∼6 dB) in order to determine the likely maximum manual detection range.…”