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Ocean Watch
By Susan Scott
Monday, January 31, 2000
During a recent visit to Sea Life Park, I watched trained dolphins propel themselves far above the water's surface, all the while turning, twisting, flipping and spinning. The dolphins performed these maneuvers on command and apparently enjoyed the interaction with their trainers. Is breaching
purposeful or
just playful?But dolphins also perform these lively acrobatics naturally. As I watched a dolphin crash onto its side with a huge splash, I remembered seeing spinner dolphins doing the same many times in Hawaiian waters.
Later that afternoon, I took a bike ride in Mokuleia and stopped to rest on a rise overlooking the ocean. I had just swigged a drink of water when an enormous humpback whale rose from the water, turned on its tail and crashed to the surface on its back.
I have seen this behavior in humpbacks before but this episode was particularly thrilling: The whale breached 11 times before it rested.
Why do whales and dolphins jump from the water like that? It's an age-old question.
Back in the bad old days, whalers thought humpback whales breached out of pure joy. Because of this, the hunters nicknamed the species the merry whale.
But modern researchers aren't so sure that breaching whales and leaping dolphins are simply having a good time. Some more practical proposals for the reasons behind breaching are that whales are trying to stun fish for feeding or attempting to dislodge parasites, such as barnacles or lice.
Another theory suggests that whales and dolphins breach to signal others nearby.
But these explanations have some holes. First, humpbacks don't eat much, if ever, while in Hawaiian waters. During the food-rich summers off Alaska, these whales gorge on shrimplike krill and small fish, like herring, by the ton. This big calorie load lasts the whales throughout their winters in Hawaii, a good thing since there isn't much whale food around here.
The ridding-themselves-of-parasites theory also is weak because most humpback whales, all of which breach, are loaded with barnacles and lice. Researchers have found humpback whales with as much as 1,000 pounds of acorn barnacles attached. Whale lice, spidery parasites with 10 strong claws each, live at the base of these barnacles. If the barnacles don't fall off during a breach, neither do the biting lice.
The theory that breaching is a signal to other whales and dolphins has been studied extensively in Hawaii's spinner dolphins. Researchers believe that when spinners are traveling, the dolphins swimming at the outer edges of the pod breach. In this way, all the dolphins in the group know the boundaries of the pod.
For humpbacks, however, the signal theory of breaching isn't as convincing mostly because as the size of a humpback pod increases, the frequency of breaches within it decreases. Also, humpback whales sing songs, a means of sending messages that requires much less energy than a leap from the water.
One current conjecture about breaching is that it is the endpoint of some underwater behavior that we humans have yet to understand. Another is that humpbacks, and perhaps dolphins, leap from the water for a look around. Researchers have found that breaches occur more often around boats than other places, suggesting that the animal may be looking for boats it can hear but cannot see under water.
Whales and dolphins may or may not be jumping for pleasure but there is one fact we all know for sure: It's a pleasure watching them do it.
Marine science writer Susan Scott's Ocean Watch column
appears Mondays in the Star-Bulletin. Contact her at honu@aloha.net.
