>
To: Journey North
From: Anne Smrcina
Stellwagen Bank National Marine Sanctuary
Plymouth, Massachusetts
The right whales are on the move --
Marilyn Marx reports that the Center for Coastal Studies research team saw 2 new mother-calf pairs in Cape Cod Bay on Friday, April 5, in addition to lots of juveniles and adults. The new mothers are Pediddle (named because of a spot on her left side that looks like one headlight) and Stripe. This brings the total of mother-calf pairs to 3. The US Coast Guard reported seeing several right whales in the Great South Channel (which is located southeast of Nantucket Shoals and west of Georges Bank).
And some more good news. Amy Knowlton from the New England Aquarium just returned from a trip down south where she and a team of researchers were able to compare three sets of data. This photo identification work seems to indicate that there are a lot more calves than previously thought. The total count now is 21 new calves for the 1995-1996 season. The researchers are excited about this news, for they were hoping for a good calving year. Their predictions for calving rates are based on the number of females of reproductive age who have not had calves in the last 3 years or more (right whales calve every 3-5 years on average). However, there were still many more than 21 whales that should have reproduced (due to the very low rates in 1993, 1994 and 1995), so the right whale population still isn't out of the woods.
Amy notes that this year there was a lot more survey work than in past years, with groups from the Georgia Department of Natural Resources and the Florida Department of Environmental Protection joining the New England Aquarium with aerial overflights. The combined efforts produced lots of photographs from which she and others on the analysis team could make identifications.
The 21 calves make this a banner year (especially after the fact that last year only 7 were identified). Why this year was higher than past years is still a question the researchers have not answered. And why right whales in general seem to be reproducing at a slower rate than is biologically possible is undetermined.
The Florida/Georgia survey teams also spotted some 70-75 individual animals, not counting calves -- a number that is twice as high as normal for the southern grounds. Many of these animals were adult males and non-calving females which usually don't show up in large numbers at the calving grounds. Researchers are also puzzled by these numbers.
Researchers up in northern waters (off the Massachusetts coast) have not only been counting whales, but taking biopsy samples too. To do this they use a crossbow and a dart that can take a small plug of skin and blubber. The dart is connected to a long line which runs to the boat. When an animal is spotted, the researchers make a close approach and then shoot the dart into the skin of the animal's back (they believe the animal is not harmed in any way due to the nature of the thick skin and blubber layer -- no internal muscles or organs are even remotely threatened). The animals rarely react to the sampling procedure. The dart with sample is then pulled back to the boat.
This year to date, 6 biopsy samples have been taken that have skin and blubber. Through DNA testing of the skin samples, researchers can determine the sex of the animal, its matriarchal line (matriline), and paternity. According to Dr. Moira Brown from the College of the Atlantic and East Coast Ecosystems, past sampling seems to indicate that the entire northern right whale population can be traced back to only three unrelated families (hunting may have decimated the population to near extinction levels). At the worst case, this may have been only 3 individual females, or there may have been several animals in each matriline (a matriline is a link between female members of a family, eg, grandmother-mother-daughter). In addition to matrilines, the researchers are now trying to determine paternity to construct the right whale "family tree."
Blubber and skin samples are being sent to Dr. Michael Moore at the Woods Hole Oceanographic Institution who is looking for evidence of biological change due to exposure to persistent chemicals (chemicals such as PCBs and pesticides). Animals that have been exposed tend to induct the enzyme cytochrome P450-1A into their fatty tissues. One theory is that exposure to organic chemicals may lead to a suppressed immunological systems and greater susceptability to infections. He has been working on a variety of baleen and toothed whales, using biopsy samples from live whales and necropsy samples from strandings.
In answer to last week's Challenge Question "Do whales sleep?", here's what we know:
Whales don't sleep like us -- they are voluntary breathers meaning they have to consciously breath in and out (it's not an involuntary reaction like we have). Studies on dolphins have shown that they rest one-half of their brains at a time -- so they are "sleeping" at "half speed." We don't know much about this lower state of awareness in the great whales. Perhaps this is happening during "logging" behavior (when whales are seen quietly resting at the surface with little movement except for an occasional blow). It would seem that the whales are going into a deep "rest" rather than a deep "sleep."
That's all for now. No Challenge Question from me to you this week. Instead, I look forward to hearing from you as you send in your "Ask the Expert" questions. Look for my next report in two weeks, along with answers to your questions.
Anne Smrcina
The Next Right Whale Migration Update Will be Posted on April 24, 1996
|
|
|
|---|
