Right Whale Migration Update: March 3, 1999
Today's Report Includes:
Right Whale Sightings in Northern Waters
Whales seem to be moving in and out of Cape Cod Bay. Between 30 and 40 right whales per year, often including mothers and calves, come to Cape Cod and Stellwagen Bank and feed on the dense plankton blooms. Some days researchers see large numbers of whales and on other days they see none. The latest reports I have are from 2/24 and 2/28.
(To respond to this question, please follow the instructions below.)
Discussion of Challenge Question #3
Challenge Question #3 asked you to pose some hypotheses based on the types of information the scientists were gathering from the radiotags. Some possible hypotheses might be based on these questions:
Seeing is Believing, How About Radio-tags?
For this last question Amy Knowlton, a researcher with the New England Aquarium Right Whale Group, notes that radiotagging may have some limitations. A recent hypothesis is that the recorded time at the surface, based on the radiotags, may actually be a "minimum time." Note how the following visual observations contrast with behavior suggested by the data:
Some observations have shown that the mother may be surfacing with just her head above water and the tag (which is attached to her back) is still underwater. The recorded data would show that the whale was underwater while, in reality, she was at the surface. Other observations have shown that while researchers are getting information about the mother's time at the surface, the information might not be true for the calf. Another hypothesis is that calves spend more time at the surface than their moms.
Discussion of Challenge Question #4
Challenge Question #4 asked about the ability to follow whales with radiotags. Did you know that the tags in the right whale tracking project send out Very High Frequency (VHF) radiowaves? These waves travel outwards from the tag in straight lines. Therefore, the curvature of the earth makes a difference. From the surface of the water in a boat the researchers can get a signal from only a short distance (the bigger the boat and the higher the antenna, the farther away they can get -- in this case about 2 miles). But an airplane can get an even greater line of sight -- some 20-30 miles.
In fact, the tags ONLY send signals when they're on the surface because the radio waves cannot go through water at all!
Discussion of Challenge Question #5
Challenge Question #5 was about the direction of the tagged whales. It would seem from the last reports that the whales (mother and calf) were starting their northward migration. But -- with whales there you can never be quite sure. They have minds of their own -- and what appears to be a move north, might just be a quick jaunt to be followed by a detour in another direction. We'll really only know for sure if they are spotted along the migration route -- or when they appear in northern waters.
Long Live the Right Whale! Challenge Question #7
I thought I'd give you another Challenge Question to keep you busy until my next report. This one involves some simple math. It concerns the life expectancy of right whales. Scientists are not quite sure how long whales can live -- but they have calculated a minimum age for at least one whale. This female (#1045 -- it has no name) was first seen with a calf in 1935. She was last seen in 1995 (although she has not been seen since then it does not necessarily mean that she is no longer alive). The minimum age for calving in right whales is 5, although the average age is 9. Right whales usually calve every 3-5 years.
That's all for now. This is Anne Smrcina, education coordinator of the Stellwagen
Bank National Marine Sanctuary, signing off.
How to Respond to Today's Right Whale Challenge Questions:
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The Next Right Whale Migration Update will Be Posted on March 17, 1999.
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