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CHAPTER 1
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 (see Chapter 4), which sparked successful research on dolphin communication in captive and wild settings for decades. There was early promise in the research of John Lilly (see Chapter 3), who marveled at dolphin intelligence. Unfortunately, Lilly's work fell into disrepute when his experiments violated principles of ethical treatment with the use of psychoactive drugs and dishonored the scientific method itself. Few scientists dared to study dolphin intelligence or communication after Lilly's speculative, but wildly popular publications. But one scientist stood out and almost single-handedly redeemed studies of dolphin cognition, Dr. Louis M. Herman, an experimental comparative psychologist who conducted some of the most original and important experimental work on dolphin cognition (see Chapter 3). His methods were based on behaviorist traditions, using operant conditioning — such as positive and negative reinforcement, so that dolphins learned to associate a category of responses with rewards (fish). But his discoveries went well beyond traditional learning paradigms. Herman's research institute, the Kewalo Basin Marine Mammal Laboratory (KBMML) in Honolulu, Hawaii, differed from most other cognition laboratories in that it was solely dedicated to research. Today, several aquaria allow for research, but the animals are also for public display, sometimes "swim-with" programs, and entertainment.
FIELD RESEARCH
Exciting new field research methods have provided a window into dolphin and whale societies that was unimaginable only a few decades ago. Since the 1970s, scientists have moved from making inferences from dead whales killed for profit to the long-term study of individuals over multiple generations. This exciting work has opened new insights into the complex social world in which these animals live, in which the nature of social relationships can determine success or failure of an individual over the course of its lifetime.
INDIVIDUAL IDENTIFICATION
The study of wild cetaceans over the long term is a fairly recent phenomenon. Two long-term studies were established in the 1970s and both continue to this day. Randy Wells pioneered research on bottlenose dolphins in Sarasota Bay, Florida, and Michael Bigg and his colleagues began to study killer whales in Pacific waters off British Columbia. The key to these long-term studies was the ability to identify individual animals through photographs, a method often described as photo-ID. In 1977, Bernd and Melany Wursig published a landmark paper in the journal Science showing that the dorsal fins of bottlenose dolphins in Argentina were individually distinctive and could be used to follow individuals across years. Biologists quickly found numerous ways to identify their subjects, from patterns of saddle patches and dorsal fins on killer whales, to fluke pigmentation on humpback whales, to right whale callosity patterns. By using these natural markings, researchers could identify their study subjects with nothing more than a good-quality photograph.
SURVEYS
Observational methods were quickly developed to determine which animal was associating with whom and where. These survey methods can be opportunistic, recording the identities of dolphins or whales where and when you find them, or can use more systematic transect methods, in which observers move along a predetermined line and sample all groups within some distance from that line. Such data are useful for determining the distribution, abundance, and habitat use of individuals and populations. Most surveys are boat-based, but some studies of migrating whales or of cetaceans in small bays are collected from vantage points on shore. Aerial surveys (and more recently drone-based imagery) can be used to study dolphin and whale populations over larger distances. During a survey, observers typically record the location (latitude and longitude) of a group, photograph all individuals, and determine their general behavior, which typically falls into four types: foraging (feeding), resting, socializing, and traveling. Group membership is usually defined by distances between individuals (for example, all whales within a hundred yards of each other are part of the same group). Ecological data might be collected such as water depth, habitat, and sea state. As will be discussed extensively in Chapter 5, surveys are extremely useful for determining social structure and the strength of bonds within a population.
FOCAL SAMPLING
In the 1980s, scientists initiated a study of wild bottlenose dolphins in Shark Bay, Western Australia, a remote and unspoiled UNESCO World Heritage Site. Here, in shallow and pristine waters, scientists could observe the fine-scale details of dolphin behavior and social interactions, much like other scientists had achieved from the study of terrestrial species such as primates, lions, elephants, and hyenas.
The Shark Bay dolphins have fairly restricted ranges, so it was relatively easy for scientists to stay with an individual dolphin for many hours using a small boat. This allowed researchers to use a method known as "focal sampling" in which the behavior of an individual or a mother–calf pair is systematically collected over a study period. For example, an observer might record the behavior of the mother, her calf, and the distance between them every minute for a period of several hours. Bottlenose dolphins live in a dynamic "fission–fusion" society (see Chapter 5), meaning that membership of their group changes throughout the day. Focal sampling enabled observers to track these changes from an individual's perspective, while collecting detailed information on location, habitat, and other important contextual details. The same individual can be followed on many days, allowing researchers to build a more complete picture of their behavior and enabling us to address questions such as: Are there individual differences in maternal care? Does maternal behavior change based on experience or the sex of the offspring? Focal sampling is also useful for examining the detailed nature of social interactions, such as who plays, fights with, or grooms each other.
CASE STUDY: FOCAL SAMPLING
In the late 1980s, Janet Mann began a long-term study of bottlenose dolphin adult females and their offspring in Shark Bay, Western Australia. With a background in primates, and training from Jeanne Altmann who pioneered standardized quantitative behavioral methods, including focal animal sampling, Mann began following mother–calf pairs for 1–9 hours a day from a 13-ft (4-m) dinghy. She began this work with her graduate school advisor, Barbara Smuts, also a primatologist.
DATA COLLECTION
Data collection involved a list of mothers and their nursing calves, which were searched for and subsequently observed for multiple days each year from birth through the period of weaning. Systematic data were collected every minute, including mother–calf proximity, activity, and what other dolphins were present. Location and habitat were recorded as well. Detailed events, such as petting (flipper stroking of another dolphin), synchronous breathing, and other interactions were recorded for both mother and calf.
MOTHER–CALF PAIRS
Early on, two mother–calf pairs stood out: Crooked Fin and her son Cookie, and Yogi and her son Smokey. Both mothers were loners and spent little time with other females, but Cookie and Smokey would frequently separate from their mothers, traveling hundreds of yards away to join up with each other and occasionally other young males, also separate from their mothers, particularly Urchin, another calf in the study. They would play very intensively and practice synchronized displays, even in the first year of life. Socio-sexual behavior such as mounting, goosing (beak to genital), and petting and rubbing were common, sometimes with or without a young female partner present. These interactions were reminiscent of adult male alliance behavior, where males (usually 2 or 3 but up to 14) cooperate against other alliances to gain access to cycling females. While such behavior might be important for adult males, it was striking to see this behavior in calves so young, more than a decade away from establishing such relationships. Mann decided, when mothers and calves separated, to remain with the calf and monitor the mother from afar, who was invariably foraging alone. Group composition was recorded every minute using a 33-ft (10-m) chain rule (dolphins within this distance of another group member were part of the group), and who joined and left the group was noted. The shallow clear water allows observers to see what the dolphins are doing. Cookie and Smokey were observed on multiple days each year.
COOKIE & SMOKEY ALONE
In 1992, Cookie and Smokey were suddenly orphaned — their mothers died within a month of each other. As both calves were now over three years old (typical weaning age), they survived their mothers' deaths. Strikingly, they now spent almost all of their time together, in very close contact, such as touching flippers ("holding hands") or resting a flipper on the other's side. We now know that the period right after weaning is risky for young males who are often the object of aggression from juvenile and adult males. By staying together, the orphans likely ensured their mutual survival. Mann continued conducting focal follows on both of them for several more years and continued to track them through surveys thereafter. Although Cookie and Smokey had ups and downs in their relationship, today — 30 years on — Cookie, Smokey, and Urchin are in a very tight adult male alliance, applying the skills they began to develop decades ago. Their remarkable story exemplifies the intricacies, investment, and importance of long-term social bonds, and what such bonds can mean for survival and reproduction.
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Excerpted from "Deep Thinkers"
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