1. A baleen whale's skull shape, jaw size, and baleen plates determine the type of prey it catches and eats.
2. The specialized filter-feeding mechanism of baleen whales enables them to feed low on the food chain by primarily eating zooplankton and schooling fishes. These food sources are often encountered in large swarms or schools.
3. Some diets may depend on food availability in feeding areas.
1. Most baleen whales spend about four to six months in the summer feeding intensively in high-latitude, productive waters and then spend the next six to eight months traveling and breeding.
2. Scientists estimate that large baleen whales eat about 4% of their body weight each day during the feeding season.
a. A blue whale eats up to 3,600 kg (8,000 lb.) of krill each day for about 120 days. It is estimated to take 1,000 kg (2,200 lb.) of food to fill a blue whale's stomach.
b. Gray whales eat about 150,000 kg (340,000 lb.) of food during a 130 to 140 day feeding period--a daily average of about 1,089 kg (2,400 lb.) . It is estimated to take 300 kg (660 lb.) of food to fill a gray whale's stomach.
3. Food intake during the feeding season exceeds daily requirements and excess energy is stored in the blubber layer. For example, gray whales gain about 16% to 30% of their total body weight during a feeding season. Blubber gained during the feeding season sustains the whale during the winter months when food is scarce.
4. During the traveling and breeding seasons, baleen whales eat much less or not at
all. Winter daily feeding rate is only about 0.4% of body weight.
1. Swimming near or at the surface of the water with the mouth open, right whales continuously strain the water for small zooplankton such as copepods.
A right whale swims at or near the surface of the water with its mouth
open. Water and food enter through a gap in the front baleen plates, and food is caught in
the matted baleen fringes inside.
a. Water and food enter the mouth through a gap in the front baleen plates.
b. The food is caught on the matted baleen fringes inside. Water exits through the sides of the mouth.
c. With long baleen plates and a huge mouth, right whales are adapted for straining immense amounts of food.
d. Right whales usually feed singly, but a group of whales may corral prey by swimming and feeding through the water in a V-formation.
2. Rorqual whales feed by gulping large concentrations of crustaceans and schooling fishes, allowing both water and food to enter the mouth. The rostrum is usually tilted upwards.
Rorqual whales feed by gulping large concentrations of crustaceans and
schooling fishes.
a. Throat grooves expand from the water pressure inside, which causes the mouth cavity to balloon outward and maximizes the water and food capacity. See also grooves.
b. The jaws are brought together and the throat grooves contract, forcing the water to drain out the sides of the mouth.
c. Rorquals may feed at the surface or at some depth. They often roll on their sides while feeding.
d. Humpback whales sometimes blow "bubble nets" to help them feed. The whale dives down, then swims in a spiral while blowing a series of bubbles by releasing air from the blowholes. The bubbles form a tubular "net," and the whale surfaces in the center with its mouth open to gulp entrapped prey. Sometimes several humpback whales come up through the bubble net one at a time to feed.
e. Some species of rorquals also use a flick-feeding method. Using the tail flukes in a quick sweeping motion, a whale can herd fish into the mouth area.
3. Gray whales feed along the ocean floor.
a. A gray whale dives to the bottom, turns on one side and sucks in water, mud, and food. Food consists of bottom-dwelling animals such as marine worms and crustaceans, which are abundant in ocean sediments.
b. The relatively short and course baleen traps food and lets the water and mud escape to the outside.
c. Scientists have documented large excavated areas on the ocean floor in gray whale feeding grounds and have observed gray whales surfacing after feeding, trailing streams of mud.
d. Gray whales may also occasionally feed in the water column on free-swimming crustaceans.
4. A baleen whale probably uses its tongue for moving food trapped inside the baleen, for squeezing water out of the mouth, and for swallowing. Baleen whales' tongues are proportionally larger than toothed whales' tongues.
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