FEEDING

7. Fast Food

Objective: Students will calculate rates of feeding for the average baleen whale, and compare the energy requirements of whales with humans.

Level: 6-7

Background: Whales consume great quantities of food, which they need to power their enormous bodies and to maintain body heat. All mammals must expend energy to maintain a stable body temperature, but this is especially difficult for whales who would lose a considerable amount of body heat to cold ocean water were it not for their blubber. The larger whales must consume 500,000 to a million calories per day. To get these calories, an average-sized baleen whale consumes 2,000 kg (4,400 pounds) of food per day during the summer. About 25% of the food is stored as fat, called blubber, which serves as both insulation and an energy reserve necessary for surviving the winter when less food is available. A typical human weighs 67.5 kg (150 pounds) and takes in 2,500 calories per day. A whale weighing about 45 tonnes needs at least 395,000 calories per day. A whale of this size may spend 15 hours a day feeding in the summer months.

Materials: pencils, paper and calculators.

Procedure:
Have the students calculate the following:
1) If a whale's mouth opening is 1.5 m2, and the average density of copepods is 9500 per m2, how many copepods can a whale ingest in one mouthful?
2) If a whale ingests 500,000 calories per day, how many calories is it ingesting per minute?
3) Investigate your own consumption figures:
a. Estimate the number of minutes you spend per day feeding.
b. If you ingested 2,500 calories in one day, how many calories would you ingest per
minute? (Hint: don't forget your answer to question 3a.)
4) Compare your caloric intake per minute with that of a whale. What factors account for the difference in intake? How does food availability differ for baleen whales and humans?