Hopefully as you read this my talks at the Symposium are done and I'm waiting to board a plane for La Paz where I'll once again be serving on the 70-passenger Lindblad Expeditions MV Sea Bird. For two weeks I will be "forced" to dive and shoot underwater video in the waters off the Gulf of California islands, and lecture for the passengers. I have to do something to pay the mortgage! To ensure you, my readers, don't suffer withdrawal, I've prepared several columns for the paper while I'm down there. I'll return just before Christmas hopefully with a few new stories to tell. Of course being back on board ship means I'll be watching whales in the "Sea of Cortez" as well.
One of the most incredible whales I've observed is the humpback. Humpback whales are members of the rorqual family like the blue and fin whales. Members of this group have dorsal fins and pleated throat pouches allowing their mouths to expand and engulf "mass quantities" of plankton (where are their manners!). Bumps in the head region each have a single hair or bristle which may be used to sense "touch." The shape and color pattern of the dorsal and tail fins are unique in each individual, just like human fingerprints. This allows researchers to follow them as they migrate based on a computerized photo identification database.
These whales are known from all the world's oceans. Although social animals, they travel in large but loose groups. Associations between humpbacks last only a few days, except for the close bond between females and their calves. Most groups follow a migration route from tropical winter areas where they calve and mate to temperate and polar regions where they feed. For example, the Hawaiian population migrates to Alaska, a distance of about 6,000 miles. Some researchers believe the migrations to Hawaii are a fairly recent phenomenon, perhaps within the last 200 years. In that state whale watching has become an $80 million dollar industry.
The humpback's body is black on top and a mottled black and white on the underbelly, extending to the lower surface of the tail fluke. The unique pattern is usually revealed when they sound (dive deep). Their equivalent of our arms, the elongated pectoral flippers (15 ft, about 25-30% of body length), may be white to black. The scientific name Megaptera means "very large wings" and theirs are the largest of any whale.
Their name comes from the arching of their back as they prepare to dive. They may dive to depths of 500-700 feet for 15-30 minutes. At the surface they use their two blowholes to breathe every 30-60 seconds, and more frequently (4-8/minute) after surfacing from a dive. The blow (exhalation) may extend 10-15 feet above the surface. Humpbacks swim at 3-9 mph but if threatened can reach more than 16 mph. Feeding speed is about 1-3 mph due to the greatly extended mouth.
Adult humpbacks are 40-50 feet long with females slightly larger than the males, and weigh 25-40 tons. To maintain this size, during feeding season they eat 3,-5,500 pounds of krill and small schooling fish a day, straining them out of the water with 250-400 plates of black baleen made out of keratin (like our fingernails). Humpbacks may cooperate in hunting food and use a unique method to concentrate their prey called "bubble netting." The group of hunters swim under the water and blow a wall of bubbles as they ascend upwards in a spiral, trapping their food inside for easy pickings. Killer whales are their principle enemy now. Like with gray whales, humpbacks are home to three species of barnacles and whale lice.
Humpbacks are sexually mature at 4-8 years and 35-40 feet depending on their gender. Females give birth every 2-3 years and carry the young for about one year. At birth the calf is 10-15 feet long and weighs 1-2 tons. It will consume about 100 pounds of the mother's fat rich (45-60%) milk each day for 6-12 months before switching to its regular diet.
While in the Sea of Cortez on the Gorda Banks north of Cabo San Lucas, I experienced a magical sunset with frolicking humpbacks all around us. These whales were swimming with their long pectoral flippers on the air, occasionally slapping them on the surface. Several did some amazing breaching, leaping entirely out of the water and doing a 360 degree role in the air. It was almost as if they could fly with their long "wings" ( look out Spruce Goose). Many of the males were "tail lobbing," raising their flukes up out of the water and slapping them on the surface. Some head lunged, thrusting their heads aggressively towards another male (control your hormones, boys). Although their purpose is unknown, many feel these behaviors are a form of communication... or perhaps they were just enjoying the beautiful sunset too.
Humpbacks are the species known for their beautiful singing (far more soothing than heavy metal or rap to my ears, although not easy to dance to). Using a hydrophone (underwater microphone) on the Lindblad Expeditions ship we were able to listen to these whales singing. These songs are complex and may last 10-20 minutes. Different populations, like those in the North Pacific, each sing their own unique song. The songs change slowly from year to year. Since males do all the singing peaking in their wintering grounds, these songs may be part of their mating behavior. Perhaps the females choose their mate just like humans choose the next American Idol?
These whales feed and mate close to shore and are slow swimmers making them easy targets for whalers. They were taken for their oil, meat and whalebone. Some 28,000 humpbacks were taken from 1905 to 1965, the year before the International Whaling Commission gave them global protection. In the North Pacific only the right whale is considered more endangered. The current population is estimated at 15,-20,000 (about one fifth of the original population).
In the open ocean drift netting was another source of mortality until the United Nations banned high seas drift netting in 1991. Pollution, largely by PCB's used in the production of plastics and styrofoam, have also affected whales. Ozone depletion due to fossil fuel burning is also a negative impact since increased levels of ultraviolet (UV-B) light reduce phytoplankton and therefore krill production. If you love whales, don't drive an SUV or Hummer (can you hear me Arnold... I mean Governator?). I have a Toyota Tercel... but mainly to support my Save Our Plankton (SOP) foundation!
© 2003 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.
The "hump" of the humpack whale; males "tail lobbing" off
finning with long pectoral fin; the "Spruce Goose" in flight
This document maintained by
Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia