To: Journey North
From: Anne Smrcina
Stellwagen Bank National Marine
Sanctuary
Plymouth, Massachusetts
Here we go with the first set of answers to your excellent questions about whales. If you don't see your question(s) here today, don't give up. I'll try to have all questions answered over the next two weeks.
1. Melanie Downing and Leah DuBose from Tallahassee, FL write: How many humpbacks are born in the Atlantic Ocean each year; how many humpbacks are born in the Pacific Ocean each year; and what percentage of humpbacks live to their first birthday?
Good questions, but unfortunately we don't have any hard and fast numbers to give you. Dave Mattila from the Center for Coastal Studies notes that most researchers estimate that the reproductive rate for humpbacks is around 5-10% a year. The last estimate for the Atlantic population of humpbacks was put at 6,000 individuals (that was about 15 years ago) so that would give us about 300-600 births a year (humpbacks calve in the Caribbean during the winter months). A new study called YONAH -- for Year of the North Atlantic Humpback -- may give us some better numbers about the present population size (which some researchers have estimated is between 3,000 to 16,000 animals). Dave notes that if a population size of 10,000 is assumed, then that would mean about 500-1,000 births a year. For the Pacific population there is an even greater dearth of knowledge about the population size, perhaps as few as 2,000 or as many as 10,000. That would give an annual calf population of 200-1,000 animals.
Many of these animals don't survive until their first birthday -- but scientists have no answer as to the exact survival rate. They are hoping that the YONAH project may provide some answers once all the data is tabluated. In one very small survey of 4 mother-calf pairs from the Gulf of Maine it was found that half the calves were lost within a year. But this is only a small sampling and not to be extrapolated for the entire population. Reasons for calf deaths may include genetic defects, inadequate food supply, pollution, entanglement, and predation from orca (killer) whales or sharks.
2. From Kathy Clark in Alaska we have these questions: How long does a humpback whale live? How long can a humpback whale stay under water? (also from Kalina Miller from Shageluk, AK). How big can a humpback whale get?
Whales seem to live as long as the average human -- about 70 years. But there may be cases of much longer life spans. Dave Mattila notes that a bowhead whale was found with a stone harpoon stuck in its body that indicates that the whale may have been at least 100 years old. And a right whale photographed in 1935 (estimated to have been at least 5 years old at that time) was also seen in 1986 in Cape Cod Bay and last year in the Great South Channel (between Cape Cod and Georges Bank) unfortunately with a large gaping wound from a possible collision. Dave says that the whale probably died from the injury, but who knows how long it might have lived if it hadn't been wounded.
Humpback whales can stay underwater about 40 minutes. Dave notes that the longest he has recorded a whale dive is 38 minutes. Here in the Cape Cod Bay/Stellwagen Bank area dives are usually much shorter -- about 10 minutes or less, with most dives in the 3-7 minute range. Depths are generally shallower here so there is little need for long, deep dives. Right whales can also stay underwater up to 40 minutes, with average dives in the 10-20 minute range.
Humpbacks can get to be about 45-55 feet in length, with southern hemisphere whales reaching lengths of 60 feet.
3. From Montana we received these questions: How do humpback whales mate/reproduce (also from the Marshall Islands)? What do they eat? How do humpback whales get along with man?
Whales are like other mammals and have similar types of genitalia (although it is coiled in or tucked under skin flaps to streamline the whale's body). Their mating behaviors are similar to other animals with competition among males for the females. For an in-depth report on right whale mating behavior see the section on reproduction in Sanctuary's new right whale book "From Whaling to Watching" now on the Internet at our home page. Fetuses are nurtured in the female's body, and the whales have live births of their young.
Humpback whales eat small fish, such as herring and sand lance at Stellwagen Bank and in Mass. and Cape Cod Bays, as well as capelin in more northern waters off the coast of Nova Scotia, Newfoundland and Greenland. They have also been known to eat (arctic) cod off Newfoundland. Another major source of food for humpback whales is krill (especially in arctic and antarctic waters).
Humpback whales seem to get along quite well with humans. Although other whales (finbacks, minkes) tend to move away from vessels, humpbacks have often been seen approaching boats to get a better look (as if they are as curious about humans, as the human whale watchers are about them). Young humpbacks have been seen (by me personally and many others) to approach boats, and then get herded back to a "safe" distance by their mothers when they get too close for comfort. Right whales are more shy. However, when they are in competitive groups, they tend to totally ignore the outside world and may get quite close to boats. The bigger question is "how do humans get along with whales." Although we have protections in place, whales are still being caught in fishing gear, hit by boats, and endangered by the pollutants we throw into the water. Even whale watching may become a problem. Too many watchers may disrupt whale feeding and breeding activities. Although we have no definitive answer on what level of human interaction is detrimental, the National Marine Fisheries Service has set up some guidelines for whale watching. Among the suggestions are: if more than one vessel approaches a whale, only one at a time can get to within 100 feet and the rest must stay at least 300 feet away without boxing in the whale; and head-on approaches are to be avoided. Further, in Massachusetts, it is illegal to approach within 500 yards of a right whale. For a detailed set of whale watch guidelines contact me at asmrcina@ocean.nos.noaa.gov and I'll send you a whalewatch guidelines flyer.
4. From Alaska come the following questions: Have tagged whales like Metompkin even been known to wander like Metompkin is? Could it be possible that Metompkin's satellite transmitter fell off and is being carried along by the Gulf Stream? and Are there any theories on the right whale's habit of "sailing"?
I'm going to take the second question first. Metompkin, the whale found entangled in debris and satellite-tagged while down south, headed up north. However, right whale researchers now believe that the tag has become detached and is floating on its own pushed by the Gulf Stream into the North Atlantic. Right whale movements, such as have been recorded for this tag, have never been seen out to this part of the ocean. However that is not to say that right whales have never been seen making long-distant voyages to strange destinations. Phil Hamilton of the New England Aquarium and Marilyn Marx of the Center for Coastal Studies both note that a mother (Wart) and her calf made a six-week trip one summer from the Bay of Fundy to a spot off the New Jersey coast; and another tagging project showed right whales exploring warm core rings and eddies off the Gulf Stream 500 miles off the coast of Nova Scotia.
Right whale sailing has been described for whales in the southern hemisphere. The whale in Cape Cod Bay was not really sailing, she was just demonstrating a personality quirk that only she exhibits. Researchers do not really understand the purpose of sailing -- it could be for cooling, for travel, or for play.
That's it for today. More answers next week.
This is Anne Smrcina signing off.
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