Tag Archives: Gray whale feeding

Gray Whales

Gray whales are one of the most-researched and best-understood species of whales. They are baleen whales, but unlike the whale species I’ve discussed the past two weeks, they are not rorquals in the family Balaenopteridae. Gray whales are the only species in the family Eschrichtiidae. You may recall that I mentioned that rorquals all have two characteristics in common: numerous ventral throat grooves and a dorsal fin. Gray whales do not have a dorsal fin, and they only have two to four throat grooves. They also differ from rorquals in several other ways. A gray whale has the coarsest baleen of any whale and the fewest number of baleen plates. Unlike rorquals, gray whales are predominantly suction, bottom feeders. A gray whale scrapes the side of its head along the ocean floor and scoops up sediment with its mouth, capturing small invertebrates in its baleen while expelling the sediment through the baleen fringes. Amphipods are the favorite food of gray whales. Gray whales are also stockier than most rorquals and are slower swimmers. They migrate close to shore, making them easy to watch and study.

The gray whale is one of the most ancient species of mammals, and it is estimated to have been on earth for approximately 30 million years. As the name suggests, gray whales are slate gray in color with gray and white patches on the skin. They are covered with abrasions, scars, and clusters of barnacles and whale lice, and they sometimes carry over 400 lbs. of barnacles and lice. Adults average approximately 46 ft. (14 m) in length, with females slightly larger than males. The average weight is 30 to 40 tons. A gray whale’s body is streamlined, and it has no dorsal fin but does have a dorsal hump about 2/3 of the way down the back. This hump is followed by 6 to 12 knobs extending to the tail stock. It has a narrow, triangular head that is arched downward when viewed from the side.

Gray whales have one of the longest migrations of any mammal. In the summer they feed in the arctic in the Bering, Chukchi, and Beaufort Seas, and in the fall they migrate to their calving grounds in the southern Gulf of California and Baja Mexico, a migration of 5000 to 7000 miles (8,050 – 11,275 km) each way. Their average swimming speed is only 3 to 5 mph (5-8 km/hr), so this migration takes a long time. On their northern migration, they pass by Kodiak Island in April and May, where they can be viewed from bluffs along the outside perimeter of the island. They are travelling and rarely stop to explore the deep bays on the island, and unfortunately, I have never witnessed their migration, which explains why I have no photos to accompany this post. The gray whales’ migration is considered a rite of spring on Kodiak, and is celebrated with a 10-day Kodiak Whale Fest with many activities, including guided trips to good whale-watching spots.

There are currently two gray whale populations, but at one time, there were three. The north Atlantic population is thought to have become extinct in the 17th century from over hunting. The Pacific gray whales were nearly wiped out in the 1850’s after the discovery of the calving lagoons in Mexico, but were partially protected in 1937 and completely protected in 1947, and since then, the eastern north Pacific population has made an incredible recovery and is now close to the original population size. The western Pacific stock, however, is endangered and is estimated to have only 101 individuals.

Gray whales have been impacted by ocean warming in recent years. Increasing sea water temperatures in the Bering Sea have reduced winter ice cover in the region, which has led to a reduction in productivity. Primary productivity in the northern Bering Sea declined 70% from 1988 to 2004, and the previously ice-dominated, shallow ecosystem that favored large communities of benthic amphipods (the favorite food of gray whales) has been replaced by an ecosystem dominated by pelagic fish. Gray whales have responded by migrating further north to the Chukchi Sea, but it is not certain what will happen if amphipod communities disappear from this region.

If you’ve spent time around gray whales, please leave a comment and tell me about your experience.  Also, if you are interested in reading sensational Alaskan true-crime stories, please sign up for my monthly Mystery Newsletter on my home page.