Sunday, December 13, 2009

Gray Whale (Behavior)

A small percentage of Gray whales feed off the Oregon coast in the summer. Their primary food source is mysid shrimp, which swarm in abundance near the bottom of the kelp beds. During this shallow water feeding behavior, watchers can often see one half of the tail fluke above water while the whale is head down in a kelp bed. The half fluke looks very much like a shark fin.

Records from the whaling industry indicate that this species usually does not feed during its migration or winter calving periods. They can lose up to 30 percent of their body weight between feeding seasons. Whales have been observed coming to the surface with mud streaming from their baleen in the calving areas and along the migration route. Such behavior may indicate attempts at feeding or training the calves to feed.

Gray whales are noted for their protective behavior toward their calves. They were called “devil fish” by early Yankee whalers who had their ships rammed and sometimes sunk after the whalers harpooned a calf to entice the mother closer. Now they are considered the “friendliest” of whales, often curiously approaching anglers and whale watching boats.

When a Gray whale comes to the surface, its blow or spout is a double-plumed, misty jet of vapor, rising 6 to 12 feet, that can often be seen against the horizon. The blow is not a fountain of water, but a mist of condensed warm moist air exhaled under high pressure from the lungs. The whale can expel 400 liters of air in a single blast.

Generally, gray whales are slow swimmers, averaging three to five mph during migration. They have a rhythmic breathing pattern. Normally they will make three to five short, shallow dives of less than a minute each and then a long, deep dive. A general rule is one short dive and a blow for every minute spent in a deep dive. This repeated breathing pattern enables the whales to store up oxygen and get rid of carbon dioxide built up during a long dive. In a single breath, 80 to 90 percent of the air in their lungs is exchanged compared to 10 to 20 percent in land mammals.

Feeding dives may range from 3 minutes up to 15 minutes. They can stay under water for 30 minutes if they need to. If they are frightened, they can hide on the bottom or travel great distances underwater. Sometimes they dive and reappear a quarter of a mile away.

Whales have the largest brain of any animal on earth. They are curious and often seen “spyhopping”, or lifting their heads above the surface of the water. They like to rise up and get a better look at their surroundings.

When a Gray whale lifts its tail flukes out of the water, it is going into a deep dive. This action, called sounding or fluking, helps propel the whale downward at a steep angle to the bottom where they feed on small crustaceans. After the flukes disappear under the water, the turbulence of the dive will cause a circle of smooth water, known as a fluke-print.

The ultimate in whale sightings is a breach, which occurs when a whale launches as much as ¾ of its body out of the water in a spectacular show of power and grace. Scientists are not sure why whales breach. They speculate that they do it to remove parasites, communicate with each other, or just do it for fun. Gray whales are not known for breaching nearly as often as their cousins, the humpback. Young Gray whales seen along the Oregon coast seem to breach the most frequently.