HOW WHALE SONGS ARE RECORDED IN THE WHITSUNDAYS

We have been recording whale songs and social noises in the Whitsundays for the last two whale seasons.  Last week I wrote about why we are recording them and about the songs.

The way we record them is using a hydrophone, which is an underwater microphone, connected to an amplifier and a recording device.

We can record humpback whales 5 to 10 kilometers away, so we don’t have to see whales, to record them.   A whale song lasts around 30 minutes and then it is repeated over and over.  The fittest whales sing the longest, so it is thought it is a way to attract a female to mate, so she will choose the one with the best genes.

We try to record for at least 30 minutes in an attempt to capture the entire song.  Because it is constantly repeated, it doesn’t matter what section we start recording it.

Often when I start the recording there are no whales in sight.   I have the engine off with the motor tilted out of the water, hold the hydrophone cable away from the hull, and try to be in a sheltered spot to avoid water splashing against the hull of the boat. Calm days are best for recording to avoid interference.   The hydrophone is extremely sensitive and picks up boat engine noises from over 10 kilometers away, as well as wind, waves, anchor chains and mooring creaking.

Even though I can only hear whales when I start recording, usually by the time I have finished multiple pods of whales have passed me, usually single mother and calf pairs.  I have had many more close encounters with whales, when I have been stationary with the motor cut to record, than when cruising around in the boat.

Humpback songs generally range from 30Hz to 15Hz.  We use a Zoom recorder and capture in WAV format.  The WAV format audio files can be analysed visually using special software to view the audio files as a spectrogram.  We upload our recordings to the University of Queensland Cetacean Ecology Group’s research data management system, where Professor Michael Noad is the director of the Centre of Marine science and Genevieve Willians is PhD Candidate.

The image below is the spectrogram of a whale song, so we can view the audio of a song.  The songs consist of a series of themes repeated in a particular order, then repeated from the start.  Within the themes are individual units joint together to form phrases.

This year we also plan to work with Dr Olaf Meynecke from Griffith University’s Whales and Climate program who is also researching acoustic whale sounds.  The traditional methods have only captured whale sounds during daylight hours.  Dr Olaf has started deploying longer term hydrophones which capture sound 24/7.  Initially the focus will be when, where and what time of day or night whales are making noises or not making noises. Monitoring the sounds and songs of humpbacks is a helpful indicator of ecosystem health.  It can help scientists understand migration activity, patterns, mating calls and competitive behavior.

For more information and to listen to a whale song please go to the Whales of the Whitsundays Facebook page.

Contributed with thanks to Whales of the Whitsundays.

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Image credit: Spectrogram of a humpback whale song, Danielle Cholewiak, NOAA/NMFS.
Basic hydrophone recording kit, consisting of a hydrophone, amplifier and zoom recorder

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