Mama Whales Teach Babies Where to Eat
Can Southern Right Whales Adapt If Food Becomes Scarce?
Feb. 9, 2009 - University of Utah biologists discovered that young "right whales" learn from their mothers where to eat, raising concern about their ability to find new places to feed if Earth's changing climate disrupts their traditional dining areas.
Related Whales ‘Chow Down' Together
For 38 years, Rowntree and colleagues have followed a group of southern right whales that migrate for three months each year to their calving area at Argentina's Península Valdés, "which is as far south of the equator as we are north of the equator here in Salt Lake City," says Rowntree, who also directs the right whale program at the Ocean Alliance's Whale Conservation Institute.
Adult southern right whales are up to 50 feet long, and their calves are about 20 feet long and weigh a ton at birth.
The whales migrate to their calving grounds in winter, when they fast, and give birth in early spring. Three months later, they travel long distances in the South Atlantic to feed for the remainder of the year on krill and on other crustaceans named copepods. Rowntree calls it "a huge chow down."
Whaling records from the 1800s and 1900s suggested southern right whales had six main feeding areas in the South Atlantic. However, scientists do not know where most of the whales feed now.
Rather than searching for right whale feeding grounds visually - an enormous if not impossible task given the lack of ship traffic in the vast South Atlantic - the scientists took a novel approach. During September and October of 2003 through 2006, Valenzuela collected small skin samples using a punch device that doesn't harm the animals.
"The skin sample is a little bigger than the size of a pencil eraser," Rowntree says.
From the skin samples, Valenzuela analyzed mitochondrial DNA, which is inherited only from the mother. The DNA revealed family relationships among whales. The researchers were able to distinguish individual whales by the patterns of whitish, callous-like material on their heads.
The skin samples also were analyzed for different forms or isotopes of carbon and nitrogen. The isotopes, which are present in food, are deposited in different tissues of the body after consumption. Food from any given location has a unique isotope "signature." That made it possible to determine which whales fed in the same place without actually knowing where the feeding areas were.
Together, the DNA and isotope data revealed which whales were related and where each animal fed.
"The main result is that individuals from particular families have very specific isotope pattern showing that animals from specific lineages feed in the same area," Valenzuela says.
Because the DNA was mitochondrial, which is passed only from mothers to offspring, the findings indicate mother whales teach their calves where to feed.The study was funded by Ocean Alliance's Whale Conservation Institute and the Canadian Whale Institute.
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