Tagging Whales in the Antarctic Seas

Flandres Bay (Sat., 6/5/10) – Last day of small boat ops… and killer whales
by -- June 8th, 2010

It’s June 5th, two weeks from Winter Solstice in this hemisphere and the morning sun is rising later each day.

The sky looked clear as we prepared boats and I was hoping the day would be as spectacular as  yesterday with the same beautiful light and magnificent mountain scenery outlining the edges of Flandres Bay.  Well the day exceeded all expectations. The weather, the scenery, the tag recoveries, acoustic tests and a special treat; a visit by some magnificent groups of killer whales made for a truly amazing final day in the small boats.

 

Golden glow, Flandres Bay

We launched three zodiacs on our last day of small-boat operations. First to launch was the tag boat in search of the first tag and to conduct biopsy samples. The prey mapping boat launched second to prey map and search for the second tag. And the third zodiac launched to search for the second tag and to conduct hydrophone (underwater microphone) acoustics tests of the sound produced by the zodiacs at different distances.

 

Fairly early out the tag boat radioed that they had recovered tag one. The prey boat and third zodiac both homed in on the second whale. The tag was still on so we followed at a distance. When the tag finally disconnected it was while the whale was under a field of newly formed “pancake-ice”.

 

Having a tag under ice is one of the most catastrophic problems we could face. We could lose an expensive tag and all of the data. Luckily both boats were very close to the release point and we could faintly hear the tag. With two boats each with tracking antennas we were able to close in and the wake from the zodiacs churned the ice enough to release the tag to the surface. Both boats raced head on to grab the tag. I got there first…

Tag recovery

 

The second major science task of the day was to test the sound-levels of the boats and acoustic transducers at different distances. This was to simulate the sound conditions as we approach animals. To do this we needed to send the N.B. Palmer out of Flandres Bay to reduce the noise levels and then had one zodiac listen with a hydrophone as the other approached at different speeds with and without the transducers pinging. We conducted 12 different test runs under different conditions.

 

While we were setting up for the hydrophone tests several groups of killer whales entered the area. A very large male with a huge, scarred dorsal fin was hard to miss on the horizon. The “type – B” killer whales moved rapidly across the bay searching for their favorite prey: seals.

Male orca

 

Three orcas

 

The whales homed in on a group of crabeater seals near the edge of an iceberg and began a coordinated attack. The tag boat was able to stay close on the scene and was able to witness the event at close-quarters; an amazing scene to witness. Let’s just say that the whales got their prey and the seals lost at least one of their group, and we got to see the apex predator of the Antarctic food web in action.

 

 Orca apex

 

 

Quite a day…

 

Pat

 

©2016 Nicholas School of the Environment at Duke University | Box 90328 | Durham, NC 27708
how to contact us > | login to the site > | site disclaimers >

footer nav stuff