Intelligence and Cognition (marine mammals)

Dolphins and sea lions are wonderful crowd pleasers in oceanaria; they leap, toss balls, swim through hoops or other obstacles, and vocalize on demand. In nature, they race toward boats, surf in the bow wave, and perform amazing acrobatics for—it seems—the pure joy of it. They are highly social, communicate, enjoy contact with humans, and appear to spend much of their time playing. It is therefore easy to understand why one of the most common questions asked by nonmarine mammal researchers is: “They are very intelligent, are they not?” This question is an excellent one, for it forces us to attempt to analyze what we mean by intelligence and how marine mammals might fit our definition of the concept.

Intelligence and cognition go hand in hand. The former refers to the mental capabilities of a human or nonhuman animal and usually is described by assessing problem-solving skills. The latter refers to the information processing within the animal and may be inferred by an analysis of how it appears to plan an action or alter it based on past experience. A “more intelligent” animal responds to an environmental stimulus faster or more accurately than the “less intelligent” one; the “more cognitive” action or animal may indicate more insight and more awareness of the problem than the “less cognitive” one. Unfortunately. past determinations of the concepts tended to be biased by our own human problem-solving skills and sensory systems and, to large degree, still are. However, we now know that indicators of intelligence can even be very different for different human societies or cultural backgrounds, i.e., within species. Can we say that the nature-living Australian aborigine who scores very low on an “intelligence” test designed with problem-solving questions of our modern industrial/electronic society is less intelligent than the student who takes the test in the industrialized world? If we answer “yes,” we should be forced to “take the test” on the Aborigine’s terms, perhaps by coming up with solutions of survival in the alternately extremely hot and cold, rugged, and food-poor outback. Similarly, it is not reasonable to study intelligence in dolphins and sea lions bv asking them to solve problems relative to our linguistic communication or hand manipulation skills (in cognitive psychology, this is called the comparative approach). It is also unreasonable to compare “intelligences” of river dolphins with those of oceanic species by asking them to solve the same problems of space or objects.

An alternative to the comparative approach of describing intelligence and cognition is often called the “absolute method.” It involves an attempt to find out how an animal thinks about things. Thinking is defined as mental manipulation of the internal representation of the external world, the stimulus. The cognitive animal is influenced to change its internal manipulations in part by past experience, and the more adept animal does this better than the “less intelligent” one. While it is difficult to judge mental processes, approximate tests and observations to do so have been devised and will be described later on.

One important window into intelligence and cognition for social species (and all marine mammals show a reasonable to very high level of sociality) is certainly communication. The individuals and species that communicate among each other in sophisticated and at times novel, interactive ways are likely the “more intelligent” (by, in this case, the prime criterion of communication) than those whose communication may be structured more rigidly or less complicated. The great U.S. ethologist Donald Griffin has argued persuasively that communication is a major “window into the mind,” not only of humans, dolphins, and other mammals, but of ants and honeybees as well (Griffin, 1981). He went on to postulate that it may be more parsimonious to explain the dance language oi bees by considering them to be aware of their actions than it is to consider them reacting to complicated chains or sets ol stimuli in unthinking (“noncognitive”) fashion. This intriguing idea is not yet widely accepted by behavioral researchers and cognitive ethologists. However, most researchers now accept the possibility of “intelligences” and cognition in nonhuman animals, potentially very different in operating modes from our own, and not testable by traditional comparative approaches.

I. Brain Size and Characteristics

A brain is needed to think and to have the chance of being aware. Within a particular taxonomic group, larger and more complex brains tend to show a crude relationship to greater flexibility of behavior, adaptive-ness to novel situations, and communication skills, i.e., intelligence. The relationship is imperfect, however, and is notoriously difficult to measure. For example, the entire brain has usually been used for descriptions of size and relative complexity, but there are motor, body function, and sensory parts of the brain that have very little to do with storing, processing, and integrating aspects of memory and thought (the latter occur only in the cerebrum).

Large mammals tend to have larger brains than small ones so brain size to body size ratios have been devised. One of these is the encephalization quotient (EQ), championed by Jerison (1973) and accepted by many researchers, albeit with often slightly different forms of calculation. The EQ is the ratio of brain mass observed to the brain mass predicted from an allometric equation of brain mass/body mass ratio of mammals as a whole. Therefore, an EQ of 1 means that the animal has an “average” brain size. It has been found for terrestrial mammals that EQs tend to be higher for those species that have few offspring, delayed physical and sexual maturity, long parental care, and generally high behavioral complexity (as estimated by degree of sociality and amount of behavioral flexibility). Examples are primates and social carnivores such as cats and canids. Within the primates, EQs tend to be higher for those in the categories just mentioned than for others, demonstrating that meaningful life history-brain size comparisons can be made at least in that group. Some aspects of general intelligence appear to be correlated with those higher EQs, from tree lemurs at the low end of the scale to the great apes at the pinnacle. Nevertheless, the very concept of EQ represents a general statement for potential comparison within or between taxa, but does not represent a fundamental phenomenon per se.

Polar bears (Ursus maritimus), sea otters (Enhydra lutris), and pinnipeds have EQs around 1, as predicted by the overall regression line of brain weight to body weight among mammals. Their brains tend to weigh between 0.1 and 0.3% of their bodies. In other words, there is nothing unusual in brain size of these mammals relative to their terrestrial carnivore cousins. Because brains are energetically expensive, it has been postulated that those of pinnipeds that dive to great depths and hold their breaths for long periods of time might be smaller. At first glance, this appears to be the case for such divers as Weddell (Lcptonychotes weddellii) and elephant seals (Mirounga spp.), but an analysis by Worthy and Hickie (1986) showed that brain size and dive capability have no clear relationship.

Dolphins and whales have large brains but not all have large brain to body weights or EQs. The sperm whale has the largest brain on earth, weighing about 8 kg. This brain is in a body that weighs about 37,000 kg, however. The brain is only 0.02% of the weight of the body, or one-fifth of the size ratio of the smallest-brained pinnipeds. However, at large sizes, a straight-line allometric comparison is probably not fair by any measure, and perhaps the body of the sperm whale (Phi/seter macro-cephalus) simply does not need relatively much brain mass for muscle movement, skin sensation, visceral action, and so on. The common bottlenose dolphin (Tursiops trumcatus), however, has a brain weighing 1.6 kg in a body that weighs about 160 kg, making it—at 1% of body weight—one of the largest relative brains on earth. This competes onlv with several other dolphins, great apes, and humans (whose brains are about 1.5 kg in a 65-kg body, or about 2.3%) (Table I).

Baleen whales, like sperm whales, have large absolute brains (about 7 kg in an 80,000-kg fin whale, Balaenoptera physalus), but none have brain to body weight ratios as large as even the relatively small ones of the sperm whale. Sirenians have neither absolute nor relatively large brains, with the Caribbean manatee (Trichechus nmnatus) having a 300-g brain in a 750-kg body (0.04% of body weight). It has been postulated that the siren-ian. a herbivore, increased body size to house a large gut for processing low-energy food, and a concomitant increase in brain size was not needed to support this size. Similarly, the huge size of baleen whales allows them to have huge mouths and to fast for extended periods. Again, this is a very different allometric growth than that of a cow, for example, that is “simply” scaled up in size from a sheep.

Brain weight/body weight relationships are of general interest and have some relationship to relative information-processing capabilities. However, a larger absolute or relatively sized brain than that of another animal does not necessarily serve a “smarter” animal. The concept of intelligence is not a linear one: because there are so many “intelligences” depending on measure or the describer’s concept of what is important, intelligence is not definable in absolute terms. All of the marine mammals have well-developed cerebrums. The brains of toothed whales have especially high amounts of neocortical folding and therefore high surface areas (Fig. 1). This quality is believed to be related to thought processes and behavioral flexibility. Whereas polar bears, sea otters, and pinnipeds show a general “terrestrial carnivore” level of folding, baleen whales and sirenians have very smooth cerebrums, with minimal surface areas. Nevertheless, the internal structure of whale and sirenian cerebrums is as well developed as those of other social mammals, and there is no reason to believe that these animals are “dumber” than others based on brain size and gross morphology. Perhaps their ways of finding and securing food, without the need of sophisticated hunting strategies as by toothed whales and carnivores, coupled with some aspects of their communication and society interactions, simply do not require the elaborate neocortical folding seen in many other mammals.

TABLE 1

Brain and Body Weights of Some Marine Mammals as Compared to Humans”

“Modified from Berta and Sumich (1999). Pinniped data from original sources listed in Bryden (1972), Spector (1956), Sacher and Staffeldt (1974), Brvden and Erickson (1976), and Vaz-Ferreira (1981): cetaceans from Bryden and Corkeron (1988): and sirenians from O’Shea and Reep (1990).

Figure 1. Comparison of pinniped, Otaria flavescens (a); cetacean, Tursiops tmncatus (b); and sirenian, Dugong dugon (c) brain, dorsal views.

While much more work on brain size and sensory capabilities needs to be done, it is known that toothed whales and dolphins, who echolocate and use sounds intensively for communication, have well-developed auditory processing lobes. Pinnipeds and especially polar bears, however, have well-developed areas for processing smell.

While brain size and complexity issues used to dominate our thinking about relative intelligence, it is becoming apparent that these can give only vague indicators of complexity of thought. It is likely that brains are structured more along lines of how an animal interacts with others and with its ecology. Higher brain function is a complex mixture of sensory inputs; processing, storing, and reactions to stimuli; innovation; and retrieval and use of previously stored events. Our inability to find clear links of these with measures of brain size and aspects of gross complexity may simply be because of the relatively primitive state of cognitive science, or it could be that clear “all-encompassing” rules of relationships simply do not exist. Promising avenues for future brain studies are noninvasive electrobiological and chemobiological studies from remote sensing of brain tissue while it is undergoing particular tasks. The findings to come from such work will make our present discussions of brain function seem very primitive indeed.

II. Learning

We know that dolphins and sea lions do marvelously complex things in captivity, but we also know that most of these behaviors have been reinforced from existing simpler ones and shaped into that dramatic leap to catch a fish. It is positive reinforcement behavior, or operant conditioning, that is at work; the animal gets a food or other reward for having done a good job. Typically, a sea lion or dolphin reward is one to three small fish per performed action. This is not unlike “training” a cat to run into the kitchen when it hears the sound of a can opener or the guppies in a home aquarium all aggregating near the top when a drawer with dried shrimp is opened. Operant conditioning can be performed on just about all animals on earth, and only speed of learning and some aspects of the amount of behavioral shaping can be indicators of a measure of “smartness” or relative intelligence. The animals learn, but there is not necessarily insight to their learning.

A. Language Studies

It has long been known that dolphins have squeaks and whistles that appear to be used for communication. In captivity, bottlenose dolphins at times appear to imitate or mimic human and other sounds. These observations led an early dolphin communication researcher, John Lilly (e.g., Lilly, 1961), to attempt to communicate with dolphins by teaching them human speech. The results were a total failure, with not one clearly definable mimicked human sound; although dolphins are quite good at matching the staccato rhythm, in die form of bursts of sounds emitted in air (or underwater), of human speech. Dolphins obviously do not have the vocal apparatus to produce human speech and may not have the neural wiring for it either. Nevertheless, Lillys association with dolphins did not stop him from postulating that dolphins have great “extraterrestrial” intelligence. He used their large brains and their purported friendliness as arguments, but could not muster communicative interactions with humans as a part of the argument. Unfortunately, his popular writings have swayed countless laypersons, and a substantial “cult” of believers in extremely high dolphin intelligence and sophisticated human-dolphin communication, even at the nonverbal extrasensory level, has evolved. No other scientists have made similar claims, but the unscientific nature of Lilly’s assertions deterred many others from studying dolphin and whale communication, and early on addressing intelligence and cognition in an obviously behaviorally flexible taxonomic order of mammals. By the way, some seals and beluga whales (Delphinapterus leucas) do have the ability to mimic human sounds, and one now-deceased harbor seal, Phoca vittdina, (“Hoover”) at the New England Aquarium used to delight visitors with his rendition of simple sentences mimicked from a human pool cleaner, replete with the pool cleaner’s Maine harbor-side accent. This ability does not indicate greater intelligence than in other seals and toothed whales who do not mimic. Instead, die ability (generally found in male pinnipeds) may relate to the way the animals use natural sounds in order to work out dominance relations for mating access to females and for other social interactions.

Two researchers who were not scared off by the unfounded claims of John Lilly and who nevertheless began language communication research, were Lou Herman of the University of Hawaii and Ron Schusterman, now of the University of California at Santa Cruz. Their studies began in the 1970s and are still ongoing, with a cadre of graduate students and postdoctoral researchers.

Lou Herman’s work represents the only truly pioneering language study conducted 011 dolphins. As in some of the successful studies with chimpanzees, who like dolphins also cannot utter sophisticated human sounds, Herman uses a modified form of sign language, with volunteers’ arms at poolside “talking to” common bottlenose dolphins. This is thus a gestural, not vocal, language. While Herman and his team have delved into many fascinating aspects of dolphin abilities, the basic study goes somewhat like this. Teach a dolphin a simple sentence, such as “fetch ball hoop,” to indicate taking the ball from the hoop and bringing it to poolside. Once this command. reinforced by operant conditioning, is perfected, then the dolphin is presented with new, untrained challenges. Perhaps it is asked to “fetch hoop ball,” or either hoop or ball or both objects are replaced with novel items never before put into this context. It is clear that dolphins quickly grasp the basic concept of “object 1,” “object 2,” and “command” and act correctly a large percentage of the time. These sentence structures have been made more complicated, with similarly positive results. The dolphins are reasonably good at syntactic structure, and they also seem to be able to conceptualize general categories of items. In others words, the ball used in training can be substituted successfully by another ball, and a gestural symbol (“word “) can be made to refer to an item very specifically or to be more general, just as in human word use (Herman, 1986).

Ron Schusterman has repeated many of Herman’s studies and invented other experiments of his own, but with California sea lions (Zalophus californianus). His results are essentially the same: sea lions are also adept at learning and extrapolating from human-like syntactic structure (Schusterman and Krieger. 1986). Interestingly, the conclusions drawn by these two fine researchers are quite different, indicating the state of knowledge and vibrant nature of the field of animal language and cognition. Herman interprets his findings as the animals using language. “Fetch hoop ball” represent a verb, a direct object, and an indirect object. Schusterman. however, states that there is no reason to believe that the animal perceives this interaction as anything more than an action command and that the linguistic concept “verb” need not enter into the equation. It is true that human children, for example, do not learn language in the structured operant conditioning style as performed here. Instead, we learned (mainly) from people talking around us and from acquiring words and syntactic rules as we went along. It was not until language was already well formed that we were required in school to understand syntactic structure by diagramming or labeling the parts of sentences.

Language acquisition learning in dolphins and sea lions has taught researchers much about imitation, learning, and mental processing abilities. It is undeniable that dolphins learn the basic concepts very rapidly (sea lions a bit less rapidly) and faster than most mammals except for chimpanzees and humans. This by itself indicates a high level of that nebulous and poorly defined “intelligence.” However, whether these studies can be called language, or whether that is even an important question, is open to debate. We humans have taken human syntax and foisted it on nonhuman species. Nev ertheless, the animals have done remarkably well with what thev were given. Perhaps they can do even better as they communicate among each other with signs and symbols and emotive content for which they have evolved.

B. Inventive Dolphins

Pinnipeds, sea otters, polar bears, and sirenians show elements of learning and play in captivity, but do not show the same kind of quick thinking or innovation as do some dolphins. However, most work has been done with dolphins, so there is some element of bias. Nevertheless, bottlenose dolphins and rough-toothed dolphins (Steno bredanensis), both with very large brains, are known as “the best” of performers in ocea-naria. It is not clear whether these animals adjust better to captivity than others or whether they are innately more behav-iorally flexible than others.

One interesting story of behavioral flexibility comes from a study done on two rough-toothed dolphins at Sea Life Park, Hawaii, in the mid-1960s. Karen Pryor, then head trainer at Sea Life Park, introduced a new demonstration into her onstage performance with one of her dolphins named Malia. The intent was for Pryor to demonstrate to the audience how a previously unconditioned behavior could be reinforced by operant conditioning. In order to do so, she could not use a previously trained repertoire, but each day had to choose a simple behavior (such as a particularly high surfacing or loud blow) that the animal did and then reinforce it. After several days of this, Malia “spontaneously” recognized that “only those actions will be reinforced which had not been reinforced previously” (Pryor et ah, 1969). In order to receive rewards rapidly (or for the pure fun of it), Malia “began emitting an unprecedented range of behaviors, including aerial flips, gliding with the tail out of the water, and skidding’ on the tank floor” (Pryor et ah, 1969). None of these behaviors had been shaped, none had even been seen before in the basic repertoire of dolphin behaviors at Sea Life Park! Pryor and her colleagues then repeated the work with an untrained female rough-toothed dolphin named Hou in order to assess experimentally whether creativity could be induced by operant conditioning in another dolphin and how long it would take. The experiment succeeded splendidly, and in a few trials, Hou was also presenting a new “act” after each one that received an operant reward.

Prvor et al. (1969) discussed their results very cautiously and reminded the reader that such training for novelty can probably be successful in horses and perhaps even pigeons as well. Many students of animal behavior and intelligence agree and are content to explain the development of novel behavior as simply a trained response. However, others have taken the experimental results further and suggested that much more insight than normal is required for the animal to “learn to learn” (the great philosopher Gregory Bateson called this “deuterolearning”) and that the relatively quick manner in which dolphins “caught on” confirms their high intelligence. By the wav, similar nonverbal training of reinforcement for novel behaviors has also been conducted for humans; the humans took about as long to realize what was being trained as did the dolphins (Maltzman, 1960). For Hou and for the humans, there was a period of strong frustration (even anger, in the humans) where they had not “caught on.” They would be reinforced for a behavior, do it, and then not be rewarded for it ever again. It took some time for the “realization” to come that they then needed to exhibit a new behavior to get a reward. Once realized, the humans expressed great relief at having figured out “the problem.” whereas the dolphins raced around the tank excitedly and displayed more and more novel and body-twisting behaviors— to the obvious delight of the researchers.

An interesting observation about dolphins is that they—at least bottlenose dolphins—readily recognize images of humans and of themselves in mirrors and on television screens. Herman et al. (1990) were able to elicit correct answers from the televised image of a human giving sign-based directions, even to the point where only white-gloved hands were shown going through the signaling motions. This demonstrates that the animals were able to use representations of the gestural instructions. Several investigators have shown dolphins mirrors and real-time video images of themselves; the dolphins react to the images with curiosity and playfulness, moving their rostrums rapidly and following their own eve movements. Furthermore, the reactions to video images of other dolphins appear to indicate that the viewing animals recognize different individuals on the screen, including themselves. This indicates a “sense of self’ and has been described as an important insight into cognition. Interestingly, chimpanzees and other apes do not have this innate capability to see images on a flat screen as representations of themselves, others, or humans. They can be taught to process the images meaningfully, but only after prolonged exposure.

III. Behavioral Complexity in Nature

A. Carnivores and Sirenians

Most marine mammals are highly social, and we would expect that they have sophisticated ways of communicating with each other by showing innovative and variable behaviors in the face of social strategies and interactions. However, the less social species are obviously also behaviorally complex. Examples are polar bears and sea otters. Polar bears have a large repertoire of “sneaking up” on their generally ice-bound prey. They move against the wind, come from the side of the sun glare, and use ice obstructions and stealth in order to surprise their prey. It has been reported that in captivity, they figure out rapidly how to unlatch (and unhinge) doors in order to escape or to move from pen to open enclosure. Sea otters are tool users, prying mussels and abalone from the substrate with rocks or stones they keep cached in an armpit while not in use. At the surface, they retrieve the tool in order to break open their shellfish food; at times using the rock as a hammer and at times laying it on their stomach and using it as an anvil. Individual sea otters have preferred methods of tool use, implying learning and innovation. Polar bears and sea otters are obviously “bright,” but few behavioral studies or systematic investigations of learning have been conducted.

Pinnipeds are also behaviorally adept, and—as we have seen—sea lions can learn tricks and some aspects of language in captive training settings. They are all social mammals, especially while hauled out on land in order for males (of most species) to work out dominance relations with each other and for females to mate, give birth, and take care of their altricial (not well developed) young. Vocalizations, body postures, and smell are important aspects of communication. In the sea, most pinnipeds are less social (with the walrus being a strong exception), but they likely use more individualized but sophisticated strategies for finding and securing enough prey to survive. We expect that the animals need to periodically adapt to different types of prey, learn which could be physically harmful or poisonous, and learn how to detect and avoid large sharks, killer whales, and leopard seals. Many pinnipeds do not take their young out to sea with them, and therefore all learning to hunt and to survive needs to be without substantial help from more experienced adults. The author suspects, but has no proof for, that the brains of pinnipeds are adapted for relatively quick self-learning to survive and are less adapted or structured for social communication except as that needs to develop for procreation. Polar bears, sea otters, and sirenians would be an exception, although while generally less social then other marine mammals, mothers take prolonged care of their young while the young develop feeding and other skills. We assume, but again have no direct proof for this assertion, that the young learn more easily and completely in the presence of their mother.

B. Baleen Whales

Baleen whales are social creatures, especially during mating times. Vocal communication is extremely important to them, with druin-like sounds of gray whales (Eschrichtius robustus), long low-frequency moans of blue whales (Balaenoptera musculus). short low-frequency grunts of fin whales, and the rich repertory of groans, moans, and scream-like sounds of the right (Eubalaena spp.) and bowhead (Balaena mysticetus) whales. Whereas all whales appear to produce sounds, the most elaborate (and best-studied) sounds are the songs of male humpback whales, which likely serve as a male-male (intrasexual) dominance signal, male-female (intersexual) mating advertisement, or both. The songs are copied from listening to each other, are long and complicated, and must require reasonably formidable powers of learning and memory. Baleen whales on the mating grounds also sort out dominance relationships in either aggressive (humpback) or more gentle but highly maneuvering surface-active groups of gray whales, right whales, and bowhead whales. In the latter grays and right-bowhead groups, it is likely that multiple males allow each other to inseminate a particular female and practice a form of sperm competition instead of physical competition to increase the chances of fathering a young. It is also likely, although behavioral researchers have gathered only incomplete glimpses of the possibility, that female whales make it more difficult for some males than others to mate with them, thereby performing mate choice of preferred partners. If true, it must be important for females to gauge the relative “goodness” of males from the complicated matrix of social sounds and close-up interactions that present themselves. In right whales and bowhead whales, an adult female has only one young every 2 to 5 years. The calf gestates in her body for 1 year and then is nursed for another. This low reproductive rate means that she must take very good care of the young to attempt to assure its survival, and researchers would not be surprised at all to find that she also wants to choose the father of her young with care.

Baleen whales tend to be less social on the feeding grounds, although recent behavioral research indicates that at least some long-term bonds of affiliation persist between breeding and feeding grounds. This does not appear to be the norm, however. Generally, blue whales, humpback (Megaptera no-yaeangliae), gray whales, right whales, and bowhead whales (these five are the best-studied baleen whale species) aggregate at particular areas because of food concentrations. An aggregation due to an outside stimulus is not necessarily a social unit, although it can result in one. Some social interactions do occur, and it is even likely that the whales are paying close attention to each other in order to detect perhaps new or better feeding opportunities somewhere else. As well, blue whales often lunge into their food in tandem, apparently so as to provide a wall next to each other toward which fast-moving krill will not escape. Bowhead and right whales will swim in staggered formations of “echelons,” side by side, apparently for the same purpose (Wiirsig, 1988).

The winner in the baleen whale feeding complexity department must surely be the amazing humpback whale. Humpback whales lunge into their fish food, alone and in coordinated groups up to an observed 22 animals. They are not merely aggregated in such a case, but all lunge (from below and toward the surface) at essentially the same time, coming to the surface within about 6 sec of each other. Apparently, although this is not yet proved, there is a vocal signal at the beginning of these highly coordinated lunges. One whale signals and others follow. Hitting the prey, a huge fish or bait ball, at one time presumably allows for each mouth to be better filled in the resultant prey’s confusion than if one or a few mouths attacked. Humpback whales also flick their tails at prey and then circle to engulf it; they flick their long foreflippers forward as their mouths open, presumably to flash the white undersides of these flippers at the prey and to herd it more efficiently into the mouth. Finally, they release a stream of bubbles from their blowholes while circling around the prey and upward. The rising bubble screen forms an effective net around the prey, and the humpback (alone or with several others) then lunges toward the surface in the center of the “net,” filling its capacious mouth with concentrated prey. It is unclear how flexible the several feeding behaviors are, but it is certain that several need social coordination. It is also likely that young humpbacks need to learn and perfect the techniques, and we assume that social learning is the major vehicle to do this.

C. Toothed Whales

Toothed whales are highly social creatures, except for older adult male sperm whales who tend to be loners, some lone killer whales (Orcinus orca), and an extremely (“aberrant”) low level of singles in many species of dolphins. Some of the deep- ocean beaked whales may be loners as well, but we have no good data on this point. Whereas most species are social, there are verv different forms. Hector’s dolphins (Cephalorhynchus hectori), harbor porpoises (Phocoena phocoena), and river dolphins tend to occur in small groups of up to a dozen animals, rarely more. We surmise that in at least some of these dolphins, individuals know each other well. Pantropical spotted (Stenella attenuata) and striped (S. coeruleoalba) dolphins of the open ocean, however, travel in “herds” of thousands of animals. While there appear to be subgroups with at least some interindivid-ual fidelity, it is very unlikely that all members of the herd know each other; some may never even meet each other. However, the herd acts as a coordinated unit, traveling at the same speed (which must be near the speed of the slowest animals), turning in essential unison, often diving in synchronized fashion. If a disturbance occurs along a flank or somewhere below, e.g., a shark zooms out of depth, there is rapid information transfer from animal to animal so that the group cascades away from the perceived danger in coordinated fashion. The information transfer is so rapid that we assume that animals are aware not only of their nearest neighbors, but are “looking beyond others,” by sight when possible and probably also by echolocation. This is sort of a chorus line effect, where dancers coordinate their movements better by not merely paying attention to their nearest neighbors, but by anticipating the wave of raised legs, for example, as it (the wave) approaches. As well, it is likely that each dolphin pays attention to the vocalizations and movements of others nearby and thus integrates response information in what the great cetacean researcher Ken Norris called a sensory integration system for dolphins (Norris et al., 1994). Jerison (1986) used the idea of shared echolocation among dolphins to postulate that the animals share sensory inputs in a way that might synergistically enhance an expanded sense of “self.” A human analogy would be if several people of a group could know their world and their place in it better by sharing neural data of aggregate visual systems. Jerison postulated that this potential sharing of echolocation data might itself account, at least in part, for large dolphin brains, but we have no direct information on this provocative point.

Coordination of group movements and activities need not be a matter of high intelligence and cognition, of course; and sensory awareness and a collective sensory integration system are well developed in schooling fishes, flocking birds, and so on. Instead, we might do better to look at the complexities of social interactions to gain “a window into the dolphins’ minds” (after Griffin, 1981). Alas, we do not yet know very much about details of communication in delphinid cetaceans, but we do know enough to call it “complex.”

Dolphins in a group are constantly aware of each other. A flipper touch here, a glance there, a slow echolocation-type click, a whistle. They interact by all sensory modalities available to them. We guess (and it is only a guess) that they are constantly gauging each other, deciding dominance/subservience relationships, seeking the comforting presence of relatives or those that they have found to be helpful in previous encounters, and avoiding those that might be aggressive. We know that there are at least occasions of political intrigue. Indian Ocean bottlenose dolphin (Tursiops aduncus) males of Shark Bay, southwestern Australia, have a strong tendency to form alliances to kidnap females. They apparently do so to gain access to reproductive females—access that might otherwise not be available because these males may not be of sufficiently high dominance status or would not be chosen by the females. Interestingly, super alliances of two or more alliances form in order to steal females from another male alliance (Connor et al, 2000). Richard Connor is presently attempting to find out whether males that cooperate together in this fashion are more often closely related or whether alliances are formed along lines of friendship more than kinship.

Toothed whales appear often to be structured along matriarchal (female-based) fines. Sperm whales, killer whales, pilot whales (Globicephala spp.), and bottlenose dolphins (of at least several populations) have close ties between mother and female young even after weaning, and in sperm and pilot whales, these ties appear to last for life. This means that potential cultural transmission of knowledge, from generation to generation, is expected to flow especially efficiently along female lines. Mom teaches young, young teaches its children, and so 011. I11 a society of relatively resident killer whales of the U.S. and Canadian Pacific Northwest, female and male offspring stay within the pod for life. This society is thus socially “closed.” However, females mate with males outside, and the males mate with females of neighboring pods. Each pod is therefore re-productively matriarchal. These societies of relatively stable long-lived individuals are likely to develop behavioral cultures of their own. We have some evidence: killer whale pods have individually distinctive sound repertoires, or dialects. Individuals of pods can recognize each other easily as of that pod. It is likely, but not proved, that individuals also recognize each other as individuals by sound. In the more open but still matriarchal societies of at least one population of common bottlenose dolphins, studied by Randy Wells and colleagues, of Sarasota, Florida, male offspring develop signature whistles (individually distinct sounds) more like those of their mothers than do female offspring. The moms and female offspring stay together as daughters mature. The sons, however, leave the natal group, roam elsewhere, and only now and then interact with their natal groups as adults. It is hypothesized that the similar signature sounds of moms and sons may provide an efficient means of recognition and thereby inbreeding avoidance (Sayigh et al, 1995). Signature whistles are also copied by dolphins who are answering the original whistler. This rapid imitation may serve as a societal binding mechanism. It has been postulated that basic greetings and verbal recognition were prerequisite to the development of human language. Dolphins have the signature recognition portion of this capability (Janik, 2000).

Sound has been studied recently relative to kin and others of a society, and much more sound-based learning is likely to come to light as studies progress. This is to be contrasted with the relatively stereotyped sounds of the great apes, for example, that do not change much with age or social association (but then, in all fairness, apes are generally less vocally communicative and more visually based than cetaceans). However, it is also likely that not only vocal evidence for learning and social transmission will come to light. We have some hints, and only hints, here as well. Killer whales of Patagonia, Argentina, beach themselves in order to take sea lion (Otaria flavescens) and elephant seal pups. The beaching maneuver requires great skill, as the predator needs to gauge exactly where the prey is 011 the beach, after having seen the prey only from a distance and through murky nearshore waters, beyond the surf zone through which it needs to make its rush to the beach. As well, it needs to beach with such velocity and angle as to be certain that the spilling waves will allow it to reach deep water again. Killer whale adults have been described as making sham rushes at a beach and then waiting along the sides while young killer whales attempt the maneuver, usually clumsily and ineffectively, again and again. Now and then, the adult makes an intervening rush and then retreats to the side again. This behavior was pointed out as probable teaching by Argentine killer whale researchers Juan Carlos and Diana Lopez (1985) and has been studied in greater detail and verified since. It is unclear how well youngsters would learn beaching “on their own,” but it is likely that it is transmitted culturally, as killer whale beaching behavior is found in only several populations worldwide. In Galveston Bay, Texas, certain female bottlenose dolphins and their young follow shrimp boats much more so than others, even maneuvering into the shrimp nets to take live fish and then wriggling out again while the shrimper is underway. This activity, video taped underwater, requires skill and dexterity to avoid being entangled in the fishing gear. The dolphins who exhibit this behavior do so “with ease,” whereas others do not fish at all in this manner. Again, we wonder whether cultural learning and societal transmission of knowledge is important here. While culture has been explored in birds and nonhuman primates, very little has been written on this subject for marine mammals (but see Whitehead, 1998).

Even on an hour-to-hour basis, dolphins of a group are likely to be coordinating their activities superbly well. While there are many potential examples (and each behavioral observer has his or her favorite ones), the author prefers one that he and his wife have studied for some time. Dusk)’ dolphins (Lagenorhynchus obscurus) of the shallow waters of Patagonia, Argentina, coordinate activities to corral fish schools. It appears, and much more work is needed to properlv describe the individual behaviors, that dolphins (circling while vocalizing, tail swiping, and blowing bubbles) surround the prey ball and thereby cause it to tighten. They also herd the prey ball to the surface and then use the surface as a wall through which the prey cannot escape. Interestingly, dolphins do not appear to feed until the prey has been tightened and is at the surface. There may be a form of “temporary restraint,” with all animals working toward the common good of getting the prey secured. This coordinated activity stands in stark contrast to taking individual advantage of the prey by grabbing a mouthful here or there and causing the prey to scatter and escape. As an example, sea lions that enter the area work on their own and are highly disruptive to the herding efforts of the dolphins. While we still need to look at the details of this behavior, to see whether kin, for example, help each other more often, we assume that much communication, learning, and individual trust need to go into such coordination. It is likely, but unknown at present, that animals know each other well enough as to have preferred “working” partners and have mechanisms for detecting and effectively ostracizing those cheaters who do not help or are disruptive at critical phases of prey gathering (Wiirsig et al, 1989).

Such activities require individual recognition, concepts of strategies for dealing with different behaviors of fish schools, coordination, memory of past events, and potential teaching or at least learning from others; in short, considerable behavioral sophistication and flexibility. In New Zealand, far from Argentina and in a different deep-water environment, most dusky dolphins feed not on schooling fishes but on mesopelagic (“midwater, deep ocean”) fishes at night. It has been found that a small sub-segment of the dolphin population—the same individuals on a regular basis—travels to bays where dolphins take seasonal advantage of fish stocks to herd prey into tight balls as described earlier for Argentina. Because it is apparently the same animals doing so year after year, we believe that there might be cultural transmission of information here as well; only some have learned (or care) to take advantage of this particular foraging style.

A final example of at-times sophisticated-seeming behavior is certainly play. Almost all young mammals play, and this has been interpreted as gaining skills necessary to survive. It certainly seems like much fun as well. In dolphins and a handful of other mammals, adults habitually engage in behavior that is difficult to rationalize as anything but play. Dusky dolphins pull on the legs of floating birds, and individuals of several species perfect the balancing of pieces of kelp or other objects on their rostrums, flippers, dorsal fin, and tail. Play is not the purview of only dolphins, however. Adult baleen whales, sea lions, sea otters, and polar bears play with objects, at times for up to an hour or more. Play seems less common in phocid seals, but the imitative sounds of “Hoover” the harbor seal may have represented a fonn of vocal play. Play seems more rare (or absent?) in wild adult sirenians, but then long-term studies underwater have not been conducted.

IV. Conclusions

Marine mammals are not of one taxonomic group and live in many varied ways; we therefore are not surprised to find that they have different brain sizes and ways of adapting to their ecologies, social structures, and behaviors. Because all use marvelously adaptive behaviors to help them survive, they are all “smart.” However, such a general definition is not very satisfying. The polar bear, sea otter (and marine otter, Lontra felina, of Chile), pinnipeds, sirenians, and baleen whales all have behavioral characteristics and ways of living that might refer to “intelligences” not all that different from terrestrial mammals. Several of the dolphins (not all) stand out as being exceptionally large brained and behaviorally sophisticated; they are quick learners in captivity and have social structures and behaviors that appear to be highly complex and variable. While much of the large brains of these odontocetes may well be taken up by the neural processing required for echolocation and other senses, as has often been speculated, it is highly likely that a large part of it also deals with relationships, learning, and long-term memory of events (Schusterman et al, 1986).

Much more needs to be learned about dolphin whistle and click communication. However, it does not seem likely that their combinations of whistles and clicks can be termed “language” in the sense of putting sets of (for example) whistles together as referential communication for different objects or constructs (ideas). Instead, vocalizations seem to carry emotive content, signature information, and may well serve as an important tool for binding social relationships (Janik, 2000). Nevertheless, there are certain to be surprises to be gained from studies on delphinid communication as more information is gleaned. One important avenue for exploration is the extent to which communication and behavior have been transmitted from generation to generation, resulting in distinct cultures in such animals as sperm whales, killer whales, and several species of dolphins (Whitehead, 1998).

While we think of dolphin and other marine mammal “intelligences” and cognitive processes and realize what marvelous animals they are, it is also fair to contemplate their limits. Dolphins are beautifully tuned to the environments in which they have evolved for millions of years, but they do not necessarily have the capability to make behavioral extrapolations that seem to us very simple. A prime example is the fear (or mental incapability) of wild dolphins to leap over obstructions. This has been a major problem for the tuna purse seining industry—dolphins caught in a net could easily all leap to freedom as the net is pursed. They do not do so because it is not in their repertoire to do so and are caught (and at times entangled and killed) as a result. Only dolphins trained to leap over nets will do so or some animals that seem to have “accidentally” (perhaps the most innovative ones?) discovered the capability in nature. This article ends on this theme of focused mental capabilities because it illustrates two related points: (1) dolphins are not those “super-intelligent” beings as claimed by some aspects of the news media and many  films and (2) dolphins are indeed “intelligent” for those things that they need to solve and interact with in their natural world, but their natural world is very different from ours.