BENEATH THE SURFACE

Janet Mann & Andrew Read

HOW & WHY DO WE STUDY CETACEANS?

Cetaceans are perhaps the most extreme mammals. In terms of social systems, life history, physiological, and behavioral traits, dolphins, porpoises, and whales represent a suite of unique adaptations to a fully aquatic lifestyle. It is these traits that inspire mythology and tales about how dolphins have rescued people from shark attacks, how dolphins can heal the sick, how sperm whales take their revenge on human hunters (as in the great story of the Essex, the story that inspired Herman Melville's Moby-Dick). But these traits also arouse the intense curiosity of scientists with the underlying question: how and why have these unusual creatures evolved such extreme traits?

When ancestral cetaceans moved into the seas fifty million years ago, they underwent massive and radical changes to accommodate their new marine habitat. The development of exquisite sensory systems, such as echolocation, allow odontocetes to navigate, hunt, and communicate in murky environments. Other senses, such as smell, virtually disappeared when their "noses" migrated to the top of their heads for breathing. Physiological traits, such as body size, organ size, limbs, and beaks, underwent colossal transformation.

The brain is a most impressive organ, and cetaceans have the largest brains on Earth (see Chapter 2). The sperm whale brain weighs nearly 18 lb (8 kg). But the sperm whale doesn't have the largest brain when body size is considered. That distinction, after humans, belongs to a large number of dolphin species, with rough-toothed dolphins at the top of the list, sporting a 3 lb 5 oz (1.5 kg) brain and an "encephalization quotient" (a measure of brain size scaled for body size) of 4.95 (about twice that of our closest relative, the chimpanzee, see Chapters 2 and 3). The biggest mammal ever to roam the Earth is the blue whale, weighing in at over 400,000 lb (about 200 tons, 180 tonnes). Cetaceans dive deeper and longer than any marine mammal, with some beaked whales reaching depths of 2 miles (3 km) and, remarkably, capable of holding their breath for more than two hours. And, cetaceans undertake the longest migrations of any mammal, with both gray and humpback whales sometimes traversing literally halfway around the world (see Chapter 6).

Another distinction of interest is testes size. Right whales have the world's largest testes, each about the size of a Volkswagen Beetle, weighing about 1 ton — a feature suggesting that males compete for fertilizations by sheer sperm count. Finally, the bowhead whale has the longest lifespan for any mammal, at more than 200 years. These extremes are fascinating in and of themselves, but they converge with other social and life history adaptations generally rare among mammals, but more common among highly social mammals such as primates, elephants, and cetaceans. Long-term study has revealed that cetaceans, and dolphins in particular, exhibit long-term social bonds, complex alliances, prolonged periods of maternal care, late maturity, and long lifespans. To understand such intriguing subjects, cetacean biologists have crafted innovative approaches to the study of animal social systems. This book explores why dolphins and whales have evolved such cognitive and social complexity and explains how we study these iconic animals.

CHALLENGES

When people learn that we study cetaceans, the first question is often "So, you swim with them?". When the answer is "no," the inevitable response is, "Then how can you study them?". Besides our lack of Olympian swimming and diving skills, there is simply no way a human swimmer can keep up with a cetacean engaged in normal activities for more than a few moments, let alone long enough to record their behavior. Cetaceans do not lend themselves to traditional observational methods typical of other studies of wild animals. They only spend a small proportion of their lives at the surface, so even the most dedicated biologist may catch only fleeting glimpses of their behavior. Cetaceans are also deep-diving and fast-moving, and sometimes migrate thousands of miles from feeding to breeding grounds; many species are only found far from shore. Following individuals for a day, let alone years, is a significant challenge. Residential coastal species, such as bottlenose dolphins, have been successfully studied in a few locations, but acquiring even basic information on most cetaceans requires creativity, tenacity, and patience. Here we illustrate how clever technologies and sheer persistence have allowed biologists to tackle the challenges of studying dolphins, porpoises, and whales.

WHALING HISTORY

Aristotle was fascinated by the biology of whales long before we knew their "economic" value, but the earliest studies of cetacean biology are firmly rooted in centuries of whaling. Fortunes were made on whale oil and baleen, so many of the keenest observers of dolphins and whales were the whalers themselves. Captains William Scoresby and Charles Melville Scammon wrote extensively about their voyages, detailed the behavior and life history of their quarry, and even speculated about their intelligence. Biologists working at whaling stations dissected massive carcasses and became familiar with their peculiar physiology and habits. One family of whalers, the Davidsons, was even successful in recruiting the assistance of killer whales (or perhaps it was the other way around) in Twofold Bay, Australia, where humans and killer whales worked together to kill migrating mysticetes (usually right whales). The killer whales ate the tongue and left the rest for the Davidsons. That relationship hinted at killer whale intelligence and cultural behavior more than a century before scientists had any inkling of these subjects (see Chapter 6). The Davidsons engaged in subsistence whaling and took fewer than a dozen whales each year, but commercial whaling was big business (see Chapter 8). By the middle of the twentieth century, most populations of large whales had been decimated, fossil fuels replaced whale oil, and our attention turned to dolphins, which were maintained for the first time in captivity.

CAPTIVE RESEARCH

Although largely dedicated to entertainment, successes with breeding, maintaining, and training cetaceans in aquaria in the twentieth century provided opportunities for research as well, predominantly with three species: bottlenose dolphins and beluga and killer whales. In the 1960s, the Caldwells, a husband and wife team, discovered signature whistles in bottlenose dolphins...