Monday, November 16, 2009

Gray Whales Feeding Habits

Midspring to midfall is the gray whales feeding season. Most of the whales spend this time off Alaska, although every summer some whales are observed feeding from British Columbia to Mexico. The summer population off the Oregon coast is about 200 to 400, with many of the same whales returning year after year.

There are two basic types of whales, toothed and baleen. The gray whale is a baleen whale. Instead of teeth, they have a row of 130–180 baleen plates that grows along each side of the upper gum line. The baleen is made of material like a human fingernail. Appearing quite stiff and solid at its outer edge, each piece of baleen is fringed inside the mouth and tapers from 3 inches wide at the gum line to nearly a point at its bottom.

Gray whales feed primarily on amphipods, shrimp like animals. They go to the seafloor and suck up an area of the bottom. Sometimes this makes conspicuous holes on the bottom. The amphipods are trapped on the baleen filter inside the mouth, while mud, sand, and water pass between the baleen plates. This is the way the whale washes the amphipods clear of sand and mud. It then uses its tongue to suck the amphipods off the inside of the baleen fringe. Since gray whales filter animals from mud and water, their baleen is stiffer and has coarser fringes than that of other baleen whales.