''PACIFIC WHALES DYING?'' : 1/3

EMACIATED gray whales are washing ashore dead. Scientists are trying to solve the mystery.

MONTEREY BAY, Calif : Tourists come here from around the world to watch whales. It's common to see humpbacks leaping out of water and fin whales slapping the waves with their flukes.

If you're lucky, you'' catch a gray whale poking its head out of water to scope out the surroundings. And if you're really lucky, you'' see a blue whale  - at up to 105 tons, the largest animal on earth.

But all is not well here this year. Gray whales are dying in large numbers. Since January, at least 107 187 North Pacific gray whales have washed ashore dead from Mexico to Alaska.

That's just probably fraction of the number that have actually died. Most will have sunk to sea floor; scientists call these carcasses ''whale falls.''

But the number of known deaths is high enough that the National Oceanic and Atmospheric Administration has declared an ''unusual mortality event'' - a pronouncement that has sent scientists scrambling to figure out what's going on.

Events like this are often the first warning sign that something maybe seriously amiss below the waves. Particularly striking is that many of the whales washed ashore have been emaciated.

Despite the toll humans have extracted on them, gray whales, which can reach 49 feet in length and weigh 45 tons, are known for their curiosity about boats and friendliness toward people.

Each spring, they migrate roughly 5,000 miles from their birthing grounds to the warm, shallow lagoons of Baga California in Mexico to their feeding grounds in the frigid waters of the Bering Sea off the Alaska coast, where they feast daily on up to 1.3 tons of mostly small crustaceans called amphipods.

It's crucial for these whales to eat enough to survive the grueling 10,000-mile-round -trip migration, among the longest of any mammal. 

When these whales returned to their Baja breeding grounds in early spring this year, they arrived weeks late and were skinnier than usual.

Now, not only do some of the adults seem to b malnourished as they pass by on their return trip to the Arctic, but we are also seeing about one-third fewer calves that we did in last year's count.

Baby whales need 50 gallons of milk a day, with a fat content of 50 percent, which means their mothers need to be well fed.

The World Students Society thanks authors : Scientist Heidi Cullen, biological oceangrapher John Ryan and Marine scientist Andrew DeVogelaere.