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Courtesy of The Dolphin Institute, taken under federal permit 942 and state permit 52
Mark Deakos measures a humpback whale escort.

Whale of a time

A new technique shows scientists
that size does matter in
undersea mating

---

By Helen Altonn
Star-Bulletin

Even in the underwater world of humpback whales, males are competitive and size wins out over sound when it comes to attracting females.

All male whales sing in a sexual display of fitness, but that apparently isn't as important to successful mating as thought.

These are among intriguing facts about the size and behavior of humpback whales being uncovered by The Dolphin Institute scientists at Kewalo Basin.

They're using a technique called "underwater videogrammetry" to measure whales and collect information about their social behavior, organization and biology.

"It's an incredible development," said Adam Pack, vice president of the institute and assistant director of its Kewalo Basin Marine Mammal Laboratory. "The technique

HOW THEY MEASURE UP The Dolphin Institute's innovative videogrammetric technique to measure whales reveals: Principal escorts -- male whales closest to the lone female in a competitive group -- are nearly 41 feet long. Other males in the group average about 38 feet. Competition is the primary mating strategy of humpback whales; singing is likely a secondary strategy used mostly by smaller subordinate males. Single females in competitive groups range from 38 to 44 feet in length and attract more and larger male competitors. Larger females are more likely to conceive and raise larger calves than smaller females. Source: The Dolphin Institute

is opening an entirely new window on the humpbacks' social behavior and reproductive strategies."

The relatively inexpensive and non-invasive technique involves a snorkeler using an underwater digital video camera and a hand-held sonar device with a higher frequency than whales can hear.

It was developed by Louis M. Herman, institute president and laboratory director; Pack, and Scott Spitz, who earned a doctoral degree at the laboratory last year with a dissertation on the technique.

"We were searching for various ways to estimate the distance to the whale -- it's kind of a moving target -- and came up with the sonar device," Herman said. "Lo and behold, that did the trick for us."

While obtaining lateral images of a whale with the camera, the sonar device records the distance from the camera to the whale. The animal's length is measured later from video images using specially designed Macintosh software.

Spitz said he was interested in the social behavior of humpbacks and thought size had an important role. "I thought it would be enlightening if we could find a way to study size and relate it to social behavior."

It was believed the biggest whales would be in competitive groups or be the singers, Spitz said.

"According to our data (reported in the recent journal Marine Mammal Science), the biggest whales are principal escorts. Dominant whales are competing for females rather than singing." The team began experimenting with objects of known length in 1997 and had a full whale program in 1998-99.

Herman began describing whale behavior from aerial surveys in 1975, and The Dolphin Institute has the world's largest catalog of photos of tail flukes and whales, Pack said.

Until the videogrammetric technique, however, whale sizes could only be estimated from boats and planes with no correlating data.

"The beauty of the technique," Herman said, "is in most cases, we are able to identify the gender of the whale and what's going on with behavior and socially ... This is going to be very exciting, to see what unfolds."

He anticipates discoveries about where juveniles are to be found, how the size of singing whales compares with that of males competing for females, and the rate of growth of calves over a winter season.

Spitz, now teaching part-time at Pikes Peak Community College in Colorado Springs, is continuing to work with Pack and Herman, analyzing data and writing reports.

He's also working with Joe Mobley, University of Hawaii-West Oahu psychology professor, on aerial surveys of whales and techniques to investigate how their size differs in various parts of the islands.

Spitz said he was most interested to learn body size is important in competition among whales.

"Among animals in general, bigger is better. I thought there might be an exception for humpbacks because they live in a three-dimensional aquatic environment where there may be more premium on speed and agility. But the data show body size is a most important factor."

Courtesy of The Dolphin Institute, taken under federal permit 942 and state permit 52
Adam Pack uses the videogrammetric technique to measure a
humpback whale mother and her calf.

Only male whales sing, Pack noted, and it was believed the singers were sexually mature. However, it appears a significant number of singers are immature and singing may be secondary to size in the male mating strategy, he said. "If you can't compete, sing."

Larger males are going for larger females, who are better mothers, Pack said. Whales don't feed in Hawaii's winter grounds, he pointed out, so the mothers must support themselves and nursing calves on stored body fat.

Juvenile whales are migrating to Hawaii, Pack said, but after two years it's difficult to distinguish between juvenile and mature animals.

The scientists can do that now with the new technique, as well as learn about the juveniles' social roles. For instance, they return early in the season to the southeast Alaska feeding grounds, Pack said.

The first to leave here are newly pregnant females, followed by juveniles, mature males and, lastly, females that gave birth, he said.

Also, in their travels here, he said, "It's almost a parade in terms of different whales coming, depending on age, class and status."

Females with calves from the year before arrive first to nurse and wean them, Pack said. Following in succession are the juveniles, mating males and resting females ready to become pregnant. Females pregnant from the winter before are the last to come to give birth after building up fat.

"We're going to find out a lot about how whales are structured in terms of social organization, how important size is in the mating game, and where the juveniles are," Herman said.

About 4,000 to 5,000 humpback whales probably come to Hawaii's reproductive grounds out of a North Pacific population of 6,000 to 7,000, Pack said.

The animals still are endangered but have been protected since 1996 and the numbers are growing.