Low-frequency sampling rates are effective to record bottlenose dolphins.

Area of Science:

• Marine biology
• Bioacoustics
• Cetacean research

Background:

• Acoustic monitoring is vital for cetacean studies but costly due to high sampling rates for echolocation clicks.
• The proportion of echolocation clicks at various frequencies is not well-documented for many species, including bottlenose dolphins.

Purpose of the Study:

• To investigate the echolocation clicks of bottlenose dolphins (Tursiops truncatus) in the western South Atlantic.
• To assess the feasibility of recording these clicks at lower sampling frequencies (24 and 48 kHz).

Main Methods:

• Analysis of echolocation clicks from two bottlenose dolphin subspecies up to 96 kHz.
• Evaluation of recordings downsampled to 48 and 96 kHz to determine click loss.
• Quantification of click loss below 24 kHz and 48 kHz.

Main Results:

• A minimal loss of 0.95-13.90% of echolocation clicks occurred below 24 kHz.
• Negligible loss of 0.01-0.42% was observed below 48 kHz.
• Recordings downsampled to 48 and 96 kHz confirmed that bottlenose dolphin echolocation clicks are captured, albeit with some loss.

Conclusions:

• Bottlenose dolphin echolocation clicks are broadband, enabling detection at lower frequencies.
• Acoustic monitoring using devices with limited sampling rates remains effective for bottlenose dolphin presence-absence studies.
• Reduced sampling rates can decrease the cost of acoustic monitoring in cetacean research.