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LatestPhoto
Chris Johnson tracking whales at 3am.
Photo: Genevieve Johnson

September 27, 2002
The Challenges of Tracking Whales at Night
  Real Audio
  28k


Log Transcript

The challenges of tracking whales.

This is Genevieve Johnson speaking to you from the Seychelles where the Odyssey is currently surrounded by sperm whales.

Four days ago in the early evening the first faint sounds of sperm whales were detected on the acoustic array - an underwater microphone we tow behind the Odyssey to find whales. They were far away but we figured out their overall direction of travel. It was only a matter of time until we caught up with them. As the Odyssey got closer to the group, it was obvious from the numerous sounds we were hearing through the speakers in the pilot house that this was quite a large group of sperm whales.

Although we were close to the group, we still had the whole night ahead of us. Tracking and staying with a group of sperm whales during the night can be quite a challenge. Chris Johnson explains-

Chris Johnson:

LatestPhoto
A line of 20 sperm whales off the port bow of the Odyssey.
Photo: Chris Johnson

When we are with whales my job is to make sure that we stay with a group and we do not lose them. So I have to be on call all hours of the night. When we are with whales the day starts at sunrise and the whole crew are on deck until sunset, that does not include the other jobs we all have like doing night watch, cooking in the galley, as well as my own work producing this website.

Sound is our guide when tracking sperm whales. The echolocation clicks produced by the whales while foraging and navigating at depth is the sound we use to pin point the bearing of the animals in relation to the Odyssey. We use a computer program called 'Rainbow Click' which visually interprets these clicking sounds. Sperm whales make regular sounds throughout their dive cycle which can last anywhere from 30 to 90 minutes in duration.

Throughout the day, we are able to visually spot the whales by looking for their blows when they come to the surface. However, at night, we have to rely solely on sound in finding and tracking sperm whales, this can be a far greater challenge.

For example, sometimes other animals such as dolphins and in particular pilot whales, have a habit of approaching the boat to ride the wave generated by the bow of the Odyssey. They will click, squeak and whistle so loudly that they can mask the sounds that sperm whales produce. Often by the time the pilot whales leave us, the sperm whales may have moved off in another direction and their clicks become faint and distant. Passing ships like tankers and fishing boats can also drown out the sounds of the whales, as well as heavy rain showers which create a lot of noise on the surface of the ocean. Therefore it is extremely important that we are aware of the whales direction and speed of travel, as well as any bathymetric features of the ocean floor that the whales may be following. This helps us understand how they are moving and helps us relocate them if we lose them.

From our recent experiences, sperm whales often cease their foraging activities for one or two hours just before dawn. Of course if they choose to rest at the surface while it is still dark, then a previously straightforward target of 15 raucous animals suddenly becomes silent. They may as well have vanished into thin air, from an acoustic perspective this is effectively what they have done.

LatestPhoto
The group drifted together along with the Odyssey.
Photo: Chris Johnson

Sometimes the whales will leave a momentary hint as to their whereabouts. These acoustic clues are relayed to the crew person on watch through the speakers in the pilothouse, in the form of 'codas'. Scientists believe that codas are used as a form of communication between socializing sperm whales. Sometimes only a single animal will coda so infrequently that it is difficult to track them, although this is an extremely effective way of keeping you on your toes at 4am! At other times a single coda from one animal will set off the entire group.

Of course after several days and nights of tracking and sampling whales, the greatest challenge on night watch is simply keeping your eyes open. We are all aware of the underlying pressure to keep in contact with the whales at night, everyone is completely dependant on one another and you don't want to be the one to let the others down. So far I have been up for 4 nights straight without much sleep but the rewards are enormous in the morning when there are whales waiting at the surface. If you lose the whales, you don't look forward to facing the crew in the morning who have spent much time and energy taking their turn at tracking before you.

Genevieve Johnson:

The Odyssey crew is now seasoned whale trackers having been at sea for over 2 and a half years and we are usually able to overcome the challenges of tracking whales at night. We have tracked this group of whales for four days and four nights now.

By 10am this morning, we collected small biopsy samples from the entire group. We turned Odyssey downwind in order to drift for a while as we cleaned up on deck and packed away the equipment in the science lab, preparing to leave this group in search of another. Around the same time, we began to hear numerous coda exchanges on the acoustic array and several whales began to surface around the boat. The blows of distant whales grew larger as they headed toward Odyssey and the main group that was rapidly expanding in number. First there were 7, then 10, then 16 and finally 20 whales lined up across the bow of the Odyssey. Drifting together, the whales seemed to accept us beside them. As the crew took to the bow and the rigging, we listened as the familiar sound of the breeze in the sails and the waves splashing against the hull, combined with the powerful blows of 20 sperm whales. What a rare sight and a humbling experience to be accepted in the company of so many whales. A rewarding and fitting end to a successful week of research.

LatestPhoto
Chris films the whales from the crow's nest.
Photo: Chris Johnson

What a privileged life we lead, living on the ocean with whales.

Log by Genevieve Johnson

 
 
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