Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Voyage of the Odyssey Voice from the Sea
What is the Voyage of the Odyssey Track the Voyage Interactive Ocean Class from the Sea Patrick Stewart
> Odyssey Logs -
Search by Region
- Atlantic Ocean
- Mediterranean Sea
- Mauritius
- Sri Lanka
- Maldives
- The Seychelles
- Indian Ocean
- Australia
- Papua New Guinea
- Kiribati
- Pacific Passage
- Galapagos Islands
> Odyssey Logs - Search by Topic
> Odyssey Video
> Current Location - Map
> A Day in the Life
> Meet the Crew
site map  
LatestPhoto
A Humpback Whale.
Photo Courtesy of Cynde Bierman

November 24, 2002
Experiences with Humpback Whales
  Real Audio
  28k


Log Transcript

My name is Judith Scott and I am the Science Coordinator onboard the Odyssey in the Seychelles. I have volunteered for Ocean Alliance on the Odyssey twice before and have also spent three summers, including this last summer as a naturalist for Cape Ann Whale Watch, Gloucester, Massachusetts, which is affiliated with Ocean Alliance.

I was thrilled to see humpback whales in the Seychelles. Hearing the whale singing live underneath the boat and spotting the blow of the tiny calf next to its mother was incredible. Even last night we heard the faint sound of a humpback whale on the acoustic array, the underwater microphone we tow behind the Odyssey. The whale watch I volunteered for in New England is located in one of the feeding grounds for Northern Hemisphere humpback whales. The whales gather there between April and October and it is estimated they spend fifty percent of their time feeding on sand lance and other baitfish found in huge numbers in the rich colder waters of the north Atlantic.

Humpback whales are baleen whales, which means instead of teeth they have 600-800 baleen plates that hang down from their upper jaw. These plates are made of keratin, the same substance as our hair and fingernails. Baleen acts like a giant filter. When the whales are feeding they take a huge volume of water into their mouth, then using their tongue they expel the water through the baleen. Unlike the water, the food does not escape as it gets stuck in the hairy fringe on the inside of the baleen. The whale uses its tongue to scrape the food off and swallows it whole. Using this method of filtering the water for food it is estimated that a humpback whale eats about 2000 pounds of food every day on their feeding grounds. During the summer months it is vital for the whales to build up stores of blubber or fat because when they migrate to the breeding grounds, like the humpbacks currently here in the Seychelles, they are thought to live off their fat deposits. Warmer tropical waters do not support many nutrients and therefore there is far less plankton, which in turn supports the huge quantities of baitfish needed for the whales to eat. Humpback whales can use 15-30% of their body weight during the winter months. This period of fasting is particularly hard for the females with calves, because they are supporting themselves and the calf on just the energy supplied by their blubber reserves. Females usually have one calf every two years, with a gestation period of 11 months. So they mate one year in the breeding grounds and then return the following year to give birth. The calf remains with its mother for 10 months to a year, presumably learning the feeding grounds and migration routes in this time. There are a number of different feeding grounds in the north Atlantic, including the Gulf of Maine, St. Lawrence estuary and areas off Greenland and Iceland.

LatestPhoto
A Humpback Whale 'lunge' feeding.
Photo Courtesy of Cynde Bierman

One of the reasons humpbacks are such a favorite with whale watchers is because of their unique feeding styles. They blow bubbles around the bait, corralling the fish into tighter balls to maximize the quantity of each mouthful. The most famous form this behavior takes is the bubble net where the whale swims below the school of fish and blows columns of bubbles in a circle around the prey. The whale then opens its mouth and comes up in the middle of the net of bubbles, consuming most of the school. There are a number of variations to the bubble technique, including bubble clouds and bubble rows. Some whales produce a single burst of bubbles in a huge cloud. This cloud can be up to 66 feet in diameter. Scientists think this may be released from the whale's mouth instead of the blowholes, like the bubble net. These methods seem to disorientate and trap the prey, concentrating it into a tighter ball, and may also prevent the fish seeing the whale's huge mouth coming towards them.

There are also many variations on these basic themes in individual whales. We can identify individual humpbacks by black and white patterns on the under side of their tails, allowing us to note the individuals feeding style. We are still unsure as to how the whales develop these individual techniques. It has been noted that females often feed in a different way to their offspring, leading naturalists on the whale watch to believe it is not nurture.

Some whales are kick feeders meaning they twist as they dive, slapping their tails on the surface before going down to blow bubbles. This may stun the fish but scientists are still unsure of its exact purpose. Others perform dragging when they surface with their mouths full, swimming at the surface using the water pressure on their throat to help expel the water from their mouths.

One of my favorite whales to see feeding is a whale named 'Catspaw'. 'Catspaw' blows bubbles and then launches a third of her body straight out of the water, mouth closed and then as she goes below, opens her huge mouth, sucking the water and food inside. It is an incredible sight and no one on the whale watch has witnessed any other individual feed in this way.

LatestPhoto
'Catspaw' bubblenet feeding.
Photo Courtesy of Cynde Bierman

When humpbacks are feeding near the surface it is a spectacular sight seeing up to a third of their bodies out of the water, and their mouths wide open, exposing the baleen plates inside. This spectacle is heightened when there is such an abundance of prey in one area that the whales start feeding cooperatively. They make brief associations with other whales in the area, not necessarily family members, and take it in turns producing the bubbles, minimizing energy consumption. Up to twenty whales have been seen feeding together in this way, a spectacular sight. These associations are fleeting because humpbacks, like most baleen whales, are usually solitary animals, unlike toothed whales such as the sperm whales we study on the Odyssey. One of the reasons for this is probably just the shear quantity of food a humpback needs to consume on a daily basis. If they were to live as a family, they would have to find that much more food each day.

So while the humpbacks in the northern hemisphere are just finishing their summer of gorging on food, making sure they have enough fat and blubber to survive the winter, the humpbacks in the southern hemisphere, like the ones here in the Seychelles, are completing their calving and breeding for this year. The calves like the one we saw are being fed enormous quantities of milk by their starving mothers so they can make the long journey south. The adult desperately needs to replenish her fat stores, as she has now used up most of her energy supplies. However, the pregnant mothers in northern hemisphere populations are now hugely fat, and after completing their 1300 mile migration, (the Gulf of Maine population migrates to the Dominican Republic) will give birth to 12 foot long calves. This entire process in the north is exactly reversed for the southern hemisphere humpback populations. How lucky I have been to see this difference first hand, coming from New England where the whales are feeding straight to the Seychelles, one of the areas where the southern whales are singing, calving and breeding.

Links

Written by Judith Scott

 
 
> Home > Voice from the Sea > What is the Voyage? > Track the Voyage > Interactive Ocean > Class from the Sea > Patrick Stewart > Help with Plugins? > Site Map