1) Brain Structure and Functions:
The shark brain has long been impugned as being tiny, simple, and relatively unimportant. Superficial examinations of the brain of small, evolutionarily conservative sharks — such as the Spiny Dogfish (Squalus acanthias) — seemed to bear this out. Experiments severing the spinal cord of swimming dogfishes, so that the brain could no longer co-ordinate swimming movements, have demonstrated that these sharks can continue to swim for several hours — although they no longer respond to changes in their swimming environment. Sharks were therefore dismissed as primitive, stupid automatons functioning almost exclusively on the basis of brutish instinct. By painting all sharks with the same biased brush, we have arrogantly denied their biological diversity and grossly underestimated their mental capabilities.
It turns out that the brains of at least some sharks are surprisingly large and complex. Numerous popular writers have characterized the brain of a full-grown White Shark as being about the size of a walnut. While this description creates a vivid mental image, it is inaccurate and highly misleading. In truth, this includes only one part of the White Shark brain, the cerebrum. The complete brain of an adult, 16-foot (5-metre) White Shark is Y-shaped and — from scent-detecting bulbs to brainstem — measures about 2 feet (60 centimeters) long. In comparison, the brain of an adult human is composed of two, wrinkly hemispheres and is about the size of half a cabbage. Of course, a full-grown White Shark is much more massive than an adult human: a 16-foot Great White weighs about 2,700 pounds (1,230 kilograms), while an ‘average’ adult human — males and females combined — weighs about 165 pounds (75 kilograms). Since large animals tend to have larger brains than small animals, a more meaningful comparison is brain weight versus body weight. In this way, the relative weight of brain tissue for each pound (or kilogram) of body weight can be readily compared among even highly dissimilar species.
A ground-breaking 1996 paper by Leo Demski and R. Glenn Northcutt examined the size and basic morphology of the White Shark brain. As their study subject, Demski and Northcutt obtained the head from a mature male White Shark that originally measured 11.75 feet (3.6 meters) in length and weighed about 950 pounds (430 kilograms). They found that its brain weighed only 1.2 ounces (35 grams), which works out to 0.008 percent of its total body weight. In comparison, the brain of a typical adult human weighs about 48 ounces (1,400 grams), or about 1.9 percent of total body weight. Thus, for each pound (or kilogram) of body weight, humans have about 238 times more brain mass than White Sharks. Yet the brains of White Sharks and humans are shaped, structured, and organized very differently from one another. Since we do not well understand how these differences affect mental capabilities, it is prudent to compare the brain weight-to-body weight ratio of the Great White to that of other sharks.
French anatomist Roland Bauchot and his co-workers have made extensive comparative studies of brain weight-to-body weight ratios in cartilaginous fishes. In an ambitious 1995 paper, Bauchot et alii survey brain size and development in 81 species of sharks, rays and chimaeras, allowing comparison with Demski and Northcutt’s 1996 findings about the White Shark brain. The brain of the White Shark is relatively large compared with that of dogfishes (family Squalidae) and skates (Rajidae), but relatively small compared with that of whaler sharks (Carcharhinidae) and stingrays (Dasyatidae). Interestingly, the Manta and devil rays (subfamily Mobulinae) have the largest brains relative to their body weight of any elasmobranch studied to date. Why these gentle plankton-grazers have evolved such large brains remains a mystery. The smallest brain among elasmobranchs is found in the Angelshark (Squatina squatina), which is a bottom-dwelling, lie-in-wait piscivore with few predators. Evidently, this lifestyle does not require a huge brain. Among lamnoids — the shark order which includes the Great White — the toothy but phlegmatic Sandtiger Shark (Carcharias taurus) has the largest brain relative to its body size, with a brain weight-body weight ratio overlapping those of some whaler sharks. In contrast, the Basking Shark (Cetorhinus maximus) has proportionately the smallest brain among lamnoids, which may reflect its placid filter-feeding habits (it doesn’t take much brainpower to outwit plankton). Therefore, compared with other actively predaceous sharks, the Great White has a brain that is roughly medium-sized relative to its body weight. In absolute terms, however, the brain of a White Shark can grow quite large because the animal itself can attain prodigious size.
Despite its sometimes impressive dimensions, the brain of the White Shark is a marvelously compact structure. Composed of countless millions of neurons (nerve cells) and supporting structures, the Great White’s brain co-ordinates virtually all of its activities — from protrusion of its jaws to delicately grasp a novel object to the thrashing of its tail to ward off a competitor. Unlike the brain of humans and most other mammals, that of the Great White is not rolled into a ball and most parts are easy to see. The White Shark’s brain is arranged in a more-or-less linear fashion, with specialized regions strung along like pearls. These regions can be conveniently grouped into hind-, mid-, and fore-brain, each of which is dedicated to a constellation of related functions.
According to Demski and Northcutt, the overall structure of the White Shark brain is fairly generalized, similar to that of the closely-related Shortfin Mako (Isurus oxyrinchus) and Basking Sharks. As in other sharks, the spinal cord of the Great White enters the back of the skull and merges imperceptibly with the hindbrain. The hindbrain forms the base of the Y and consists of two main parts, the brainstem and cerebellum. The White Shark’s brainstem bristles with the posterior cranial nerves. These include nerves responsible for conveying input from the shark’s inner ear, lateral line and electrosensory systems. Although the cranial nerves are astonishingly thick (some were initially mistaken for muscles), Demski and Northcutt were unimpressed with the brain centers responsible for analyzing acoustic, vibratory, or electric stimuli. They concluded that these senses are probably relatively unimportant to the White Shark. The White Shark’s hindbrain also contains the brain center (amygdaloid nucleus) that probably mediates instinctive fight-or-flight responses. Therefore, much as you or I might withdraw our hand or foot before we fully realize we have been punctured by a splinter, a Great White’s ‘decision’ to attack or flee in self-defense apparently occurs at a very basic level, below that of learned responses in the neural hierarchy of the shark brain. The White Shark’s cerebellum is perched atop the anterior part of its brainstem. This structure is quite large and well-developed in the Great White, highly convoluted and folded so that it is asymmetrical. As in humans, the White Shark’s cerebellum is responsible for muscular co-ordination, especially in response to sensory input. Thus, when a White Shark flinches in response to a sudden loud noise or veers toward a novel vibration or attractive electrical signal, it is obeying signals from its cerebellum.
The top of the White Shark’s midbrain features a pair of prominent swellings. These are the optic lobes, which are responsible for coordinating visual input. The central area of the White Shark’s midbrain that mediates visual discrimination is relatively small. Based on this, Demski and Northcutt suggest that this species may be less adept at resolving fine details than certain other sharks. However, the 1985 study of the White Shark visual system by Samuel Gruber and Joel Cohen reported in the previous chapter suggests that vision is well-developed in this species. Since the optic nerves and eyes are actually extensions of the brain itself, image discrimination — including fine detail and color — in the White Shark may be taken over directly by its specialized retina. Vision is clearly very important to the predatory and social life of the Great White. It has thick optic nerves and large eyes controlled by massive muscles that not only rotate the eyeballs within their sockets but also generate significant metabolic heat. This heat, in turn, may allow faster processing of visual information and increase the efficiency of visual and other neural activity. While all these features suggest that the White Shark has excellent vision, we do not know whether this is true. Formal behavioral experiments to test what White Sharks can and cannot see have not yet been carried out. Thus, for the time being, only the Great White knows for certain what it actually sees through its large, dark eyes.
The White Shark’s forebrain, however, may be the neural region of greatest popular and scientific interest. The anterior forebrain of the Great White consists of the olfactory (scent-detecting) organs and the cerebral hemispheres — the part of the brain responsible for learning and memory. It had long been thought that some 70% of the shark brain is dedicated to the sense of smell. We now know that this startling figure is based on a major misinterpretation of how the shark brain is organized. In most vertebrates, the olfactory bulbs are connected to the front of the cerebral hemispheres. It was assumed that the same arrangement occurred in sharks. But elasmobranchs are unique among vertebrates in that the olfactory tracts — forming the branches of the Y-shaped brain — fuse to the sides of the cerebral hemispheres. This arrangement creates a false impression that the olfactory organs extend far tail ward and that the cerebrum is tiny and relatively insignificant. Even today, many modern comparative anatomy and neurobiology textbooks continue to incorrectly label shark cerebral hemispheres “olfactory bulbs”, perpetuating the myth that sharks are mindless eating machines led around by a phenomenal sense of smell.
The White Shark’s olfactory organs are huge, with long olfactory tracts and well developed lamellae — which increase their surface area and thus greatly enhance sensitivity. Of all the features of the Great White’s brain, the complexity and sheer massiveness of the olfactory organs most impressed Demski and Northcutt. Based on the exceptional development of these structures, Demski and Northcutt suggest that detection of olfactory stimuli may be extremely important to the White Shark. Olfactory cues likely to be of particular importance to White Sharks are: detection and identification of potential prey; recognition of various environmental markers, such as estuaries which may serve as nursery areas or harbor concentrations of prey; and — perhaps most importantly — recognition of individual members of their species, including potential mates. In the visually concealing medium of the sea, the Great White may live in a perceptual universe dominated by scent.
But perception is only a single component of behavior. Once a stimulus is received and interpreted by the appropriate brain centers, the animal must decide how to act upon it: ignore, investigate, intimidate or evade. Whatever ‘thinking’ a White Shark does occurs primarily in its cerebral hemispheres. According to Demski and Northcutt, the Great White’s cerebrum is not exceptional, being moderate in size and degree of folding. The central area of the cerebrum is thought to be responsible for home ranging and social behavior in sharks. This region is small in the White Shark compared with that of whaler sharks. In addition, like that of other sharks, the brain of the Great White is mostly hollow — perforated by a series of irregular, interconnected chambers (ventricles) — and filled with a complex fluid (cerebrospinal fluid) that probably helps regulate the brain chemically. These brain chambers, called ventricles, are particularly large in the White shark, resulting in a brain composed of an unusually thin ‘shell’ of nerve tissue. Based on these features, Demski and Northcutt suggest that the White Shark may not patrol well-defined home ranges or exhibit dynamic social hierarchies as in the more cerebral, thicker-brained carcharhinids. Yet recent research off California, South Australia, and South Africa suggest that White Sharks move through their environment in fairly predictable patterns and seem to exhibit display behaviors that serve to establish which individuals are dominant and which submissive. We know so little about how the physical structure of the brain is manifested in that elusive specter we call ‘mind’, it seems premature to dismiss the mental capabilities of the White Shark based on the relative size of parts of its brain.
It is also worth bearing in mind that brains do more than think. For example — in addition to the olfactory organs and cerebral hemispheres — the forebrain also contains two intimately related structures, the hypothalamus and pituitary gland. Slung below the optic lobes of the Great White’s brain, the hypothalamus is important in regulating many activities vital to its survival. The hypothalamus produces hormones (chemical messengers) that regulate bodily processes and contains centers that control such life-sustaining activities as heartbeat, body temperature, metabolic rate, osmoregulation (internal salt and water balance), food intake, and digestion. Electrical stimulation of the hypothalamus has revealed that biting is also controlled by this multi-talented structure. Protruding from the top of the hypothalamus is the epiphysis, which is sensitive to day length and perhaps position of the sun; it may therefore provide information useful for coordinating navigation and migration. The hypothalamus regulates the pituitary gland and — as a result elegant feedback mechanisms — much of its activity is, in turn, regulated by the pituitary gland. The pituitary has been called the “master endocrine gland”, as it secretes the hormones that control most other ductless, hormone-secreting glands. Directly or indirectly, the pituitary controls virtually every aspect of maintaining an optimal internal milieu — blood pressure, blood sugar levels, kidney activity, growth, calcium budget, metabolic rate, blood testosterone levels, ovulation, uterine contraction, and many, many others. The hypothalamus-pituitary gland system thus quietly controls many biological processes that underlie some of the Great White’s most spectacular and evolutionarily vital behaviors — including feeding and mating.
How the White Shark translates sensory input and its brain’s internal chemistry to behavioral output largely remains a mystery. But why sharks in general have such large complex brains is far less so. A large White Shark has a brain that may measure 18 to 24 inches (45 to 60 centimeters) from the olfactory organs to the brainstem and features a relatively large, complexly folded cerebrum. Yet a scaled-up goldfish or salmon could make do with a fraction the cerebral endowment of a White Shark. All of which begs the question: what does a Great White think with all that brain?
Men’s brains are roughly the same size as those of women, but — on average — women’s bodies are smaller and lighter than their male counterparts’. As a result, the brain of a woman is typically about 2.2% of her body weight — proportionally some 27% larger than a man’s. Make of that what you will.
2) Inside the Mind of a Killer:
Our species has achieved a firm understanding of the physics of matter and energy, including how these fundamental components shape the properties of life. We understand the detailed behavior of atoms and the forces that affect them, the essential mechanisms of cells and genes, as well as the basic processes of ecology and evolution. But the mind remains one of the last great enigmas of modern science. Philosophers have speculated that our physical bodies are merely an expedient transport mechanism and that who we are as individuals are characterized by that ethereal quality we call ‘mind’. Even the deceptively simple question of what ‘mind’ is takes on the ambiguity of a Zen koan. Some psychology theorists have attempted to tackle this slippery issue by proposing a brain-mind duality, implying that mind is something fundamentally distinct from the physical structure of the brain. But this seems to me an unproductive approach, as it is not amenable to experimental testing. Every bit of neurophysiological evidence we have suggests that whatever ‘mind’ is, it is contained wholly in the tissues of the brain and nowhere else. Therefore, those human qualities we most admire and aspire to – such as love, kindness, creativity, intelligence, wisdom, bravery, honor, and so on – are all consequences of the flurry of chemical and electrical signals passing among the brain’s 10 billion neurons. Some people regard this perspective as ‘robbing’ us of our humanity, but I am not among them. That everything we do and are is an expression of the exquisite organization of otherwise ordinary atoms packed into 3 pounds (1.4 kilograms) of gelatinous goo inside our bony skulls seems an astonishing idea with awesome implications. Many other animals – including Great White Sharks (Carcharodon carcharias) – have brains that are composed of neurons and other cells that seem to function more-or-less the same way ours do. This structural similarity raises two fascinating possibilities: 1) the mental universe of animals, while somewhat different from ours, may be every bit as richly textured, and 2) the experiences and awareness of animals differ from ours largely in degree rather than kind. Our minds may have more in common with those of White Sharks than we ever dared suspect.
3) Mental Process:
Understanding what a White Shark is thinking is no easy task. It is hard enough to know what is going on in the mind of another person, let alone another species living in an environment so very different from our own. Yet, as social creatures, most of us have become reasonably good at inferring one another’s emotional and motivational states by reading their associated behavioral cues. For example, a person who consistently fails to make eye contact might be very shy or their behavior could betray a hidden sense of guilt or shame. With observation and careful reasoning, we can learn to decipher the behavioral cues of animals, too. Overt or dramatic animal behavior is easiest to observe and interpret: a hissing, glowering cat with its ears folded back, back arched and fur bristled is clearly signaling defensive threat. Subtler animal behaviors may be harder to notice and interpret. After many hours experience in the woods, for example, most hunters and wildlife photographers learn that when a feeding deer twitches it tail, it is about to raise its head to scan for potential threat. Body language and other behavioral cues can be interpreted in light of the context in which they occur and the reactions that result. Such correlations often provide powerful insights into why animals do what they do. In principle, the same approach can reveal much about the behavior of sharks – including the Great White.
Unfortunately, it is extremely difficult to observe ‘natural’ shark behavior. Despite impressive advances in shark husbandry, some species – such as the White Shark – have not been maintained in captivity long enough to learn much about their behavior. In addition, the behavior of captive sharks is often muted or altered due to a combination of cramped and crowded living conditions, easy and predictable feeding, and frequent interaction with humans. Observing shark behavior in the wild is fraught with inherent logistical challenges. Sharks are large, far-ranging animals and some – like the Great White – are potentially very dangerous. Little meaningful shark behavior can be observed from the surface, as most species are strongly associated with the sea floor. Underwater, vision is highly restricted and most sharks prefer to maintain a cautious distance from humans, often approaching no closer than the limit of visibility. Sharks can be lured in for close observation and filming by using bait, but this creates new problems. In baited contexts, shark activity is focused on the food and inhibited by proximity to human observers and other unfamiliar objects. No matter how tempting the bait, even the mighty White Shark often seems intimidated by the closeness of boat, shark cages and bubbling divers. If several sharks are drawn to the bait, a competitive factor reduces feeding inhibition but forces the sharks to come uncomfortably close to one another. The resultant behavior is socially tense, representing an uneasy balance between peaceful feeding and defensive fighting. Therefore, much of what we think we know about shark behavior based on captive or baited animals may be highly misleading.
I am very fortunate in that I have been able to spend many thousands of hours in the ocean observing some 45 species of sharks under a wide variety of baited and non-baited conditions. Alas, until quite recently, I have had relatively little opportunity to observe free-swimming White Sharks, almost all of which occurred in baited contexts. Fortunately, due to its larger-than-life reputation, the Great White is one of the most filmed and photographed of sharks. Although the vast majority of White Shark observations are based on animals that had been lured with bait, some unexpected behaviors have been reported among all the usual biting and gorging and slamming into cages. In addition, newer technologies – such as sonic telemetry and autonomous cameras attached to individual sharks – are revealing intriguing aspects of the secret life of the Great White Shark. As a result of my own underwater observations, combined with those of other diving naturalists and marine biologists, some general patterns of shark behavior are resolving into crisp focus. Perhaps most remarkably, it is becoming clear that – despite its exceptional size and many unusual adaptations – the Great White behaves very much like other sharks.
So what can be deduced about the mental processes of sharks in general and the Great White in particular? As creatures having a large, well-developed brain, it comes as little surprise that sharks are conscious. That is, they seem to have a well developed sense of self and non-self, recognizing themselves as distinct from the environment through which they swim. I and others have observed sharks delicately maneuvering just enough to avoid colliding with obstacles (coral heads, divers, anchor lines, shark cages, etc.) in their liquid environment. This suggests that sharks realize that the objects they see are real, having a solidity that can injure them or impair their movement. As predators, sharks can recognize prey and non-prey. Identification of potential prey animals is most likely accomplished through evaluation by various sensory systems – scent, sight, touch, taste, and so on – tempered by experience. Rejection of non-prey animals and inedible objects often depends on tactile and chemical cues obtained when an object is actually in the shark’s mouth. There are numerous reports of sharks rejecting food apparently on the basis of texture or taste. Consider the example of White Sharks biting but not swallowing Sea Otters (Enhydra lutris). As opportunistic hunters, sharks must also be able to apply various stalking and capture strategies for different types of prey, being able to modify their predatory strategies ‘in hot pursuit’ to anticipate their dinner’s likely escape tactics and take advantage of unexpected changes in strategic advantage.
Like many other social vertebrates, sharks can apparently recognize members of their own species. Whether this is accomplished by scent, sight, or some other sense is not yet clear. However they do it, species recognition is obviously important for reproduction. If it is to breed successfully, a shark must recognize a member of its own species and determine its readiness to mate. Further, as animals that achieve fertilization through copulation rather than spawning, males and females must communicate their intentions are amorous rather than aggressive – a consideration that is particularly important because both participants are literally armed to the teeth. In addition, many sharks form loose, single-species aggregations – especially as juveniles, when risk of predation is greatest. A few shark species – such as the Scalloped Hammerhead (Sphyrna lewini) – form true schools, the structure and function of which apparently varies from location to location. To date, no one has reported schools of White Sharks, but newborns of this species may form loose aggregations for protection from predators.
Sharks are also able to recognize their social rank among their own and other species. The rank of an individual shark among conspecifics seems to be largely – but not entirely – based on size. In January 1980, ichthyologist John McCosker observed an 11-foot (3.4-metre) White Shark displaced from feeding by a 14-foot (4.3-metre) White Shark, which nipped its smaller competitor on the nape and then proceeded to feed. Clearly, in this context, the larger shark was dominant over the smaller. Based on my own observations of reef-dwelling whaler sharks, in competing for localized bait, a shark will defer to a conspecific as little as 5% larger than itself. This suggests that sharks have a good awareness of their own body size and a keen ability to compare their dimensions to that of conspecifics. I and other field researchers have learned that, in the wild, certain shark species appear to be dominant over others. For example, in a classic 1963 paper, Conrad Limbaugh noted a definite “pecking order” among the various shark species at Clipperton Island, located some 600 miles (970 kilometres) southwest of Mexico. Among sharks of nearly the same length, Limbaugh noted that the Silvertip Shark (Carcharhinus albimarginatus) is clearly dominant over the Galapagos Shark (Carcharhinus galapagensis), which is dominant over the very timid Blacktip Shark (Carcharhinus limbatus). Inter-specific dominance hierarchies apparently also develop in captivity. During a 16-day period in 1981, Sea World of California held captive a 5.5-foot (1.7-metre) White Shark in its large communal shark tank. An 8-foot (2.4-metre) Bull Shark (Carcharhinus leucas) that usually dominated all the sharks in its tank avoided the White Shark and when these two sharks were on a collision course, the larger shark consistently gave way to the smaller. What makes this case particularly interesting is that the formerly dominant Bull Shark is unlikely to have previously encountered a White Shark. Yet somehow it knew that the smaller shark was not to be trifled with.
Considering their sensory sophistication, ecological role as opportunistic predators, need to secure intimate co-operation for successful mating, and dynamic social hierarchies, the large brain that is characteristic of sharks simply makes sense. From observations of its behavior in captivity and in the wild, it is becoming clear that the White Shark, too, needs its large, complex brain to function effectively in its day-to-day life. But what is perhaps most intriguing is how the White Shark behaves when faced with novel situations. How the Great White responds to unusual objects in its environment reveals astonishing things about this shark’s mental universe.
4) Killer Instinct and Learning:
The traditional view of shark intelligence is that they have none to speak of. It was taken for granted that a given stimulus would generate in any shark a specific, un-learned response. This response would be performed the same way, time-after-time, independent of context or probable survival value. In short: sharks were deemed to be little more than mindless automatons.
It had long been assumed that, like other sharks, the Great White operates largely on the basis of instinct. Instinct may be defined as a highly stereotyped (performed the same way each time) behavior, usually directed toward objects in the environment, that is more complex than simple reflexes. Certain instinctive behaviors may be modified through learning, but most tend toward a narrow, predictable response. Examples of instinctive behaviors in the White Shark include rolling the eye tail ward when the snout touches an object and body language elicited in social contexts. Observations of baited White Sharks reveal that most individuals quickly learn that the bait, nearby boat and shark cages do not represent a threat to its eyes. In response, the eye-rolling behavior is greatly reduced and may discontinue altogether for as long as an individual shark is feeding in that now-familiar situation. This is an example of habituation. If, however, a human boldly — and ill-advisedly — reaches out to pat an inured White Shark on the head, the eye rolling behavior is likely to re-appear. Similarly, White Shark display behavior (body language) tends to be highly stereotyped. Yet this response, like the eye rolling behavior, is often muted with frequent exposure to the same context, as in areas where organized shark feedings are regularly choreographed for the benefit of tourists. It seems very likely that, when such intimate behaviors become better documented and understood, White Shark precopulatory rituals are also highly stereotyped.
As opportunistic predators that must perennially be willing to exploit new food resources, sharks often display overt curiosity toward novel objects in their environment. Porbeagles (Lamna nasus) off the Cornish coast seem to be utterly fascinated by the balloons that sport anglers use to hold their baited hooks a set distance below the surface. A fascinating 1996 paper by Wesley Strong demonstrated that, given a choice between a floating seal-shaped decoy and a floating plyboard square of comparable surface area, 9 to 31% of White Sharks tested off South Australia preferentially approached and visually inspected the square. There are numerous reports from South Australia and the Farallon Islands, California, of White Sharks slowly gliding past and even languidly circling professional abalone divers before peacefully swimming away. At no time did these sharks show any sign of aggression toward the divers; they merely gave the distinct impression of swimming by for a closer look at the unfamiliar phenomenon of a clumsy, bubbling biped. In a provocative 1996 paper, shark researchers Ralph Collier, Mark Marks, and Ronald Warner examined cases of White Shark attacks on inanimate objects along the Pacific coast of North America. Collier and his colleagues found that a wide variety of floating objects had been bumped and/or nipped by White Sharks and they noted that it seemed to make little difference what color, shape, size, or kind of movement (minimal, constant, or erratic) the objects had when struck. The only factor that seemed consistent among all cases was that the object was at the surface when struck, although this could represent observer bias — as surface-bound creatures, we have virtually no idea how often Great Whites or other sharks strike inanimate objects underwater. What is intriguing about these cases, however, is the fact that relatively little damage was inflicted against the objects struck by White Sharks — suggesting that the animals were examining rather than attempting to eat them. This, and other behavioral evidence, strongly suggests that the Great White experiences curiosity.
Sharks were long presumed to be too primitive and stupid to be capable of learning. In a pivotal 1963 paper, ichthyologist Eugenie Clark demonstrated that captive Lemon (Negaprion brevirostris) and Nurse (Ginglymostoma cirratum) Sharks could learn and remember as well as some mammals. In as few as 10 trials, some of the Lemon Sharks learned to press their snouts against a submerged plyboard target and wait for an underwater bell before returning to a specific part of the pool to receive a ‘reward’ of food. This association of an action and a sound with the imminent arrival of food is an example of conditioning. By the end of the first week, all the sharks of both species learned to perform this task. When the water cooled in winter, the sharks lost interest in feeding and the experiment was temporarily suspended. But when the waters warmed in the spring — some 10 weeks later — the sharks were once again presented with the underwater target. To everyone’s astonishment, the sharks performed perfectly, as though they had not lost a single day’s practice.
Of course, pressing targets and ringing bells have little or no relation to feeding in the lives of wild sharks. Zoologists Robert Jackson and R. Stimson Wilcox have demonstrated that — despite their tiny, simple brains — jumping spiders of the genus Portia can learn to hunt other spiders using trial and error. Surely sharks — with their much larger and more complex brains — can also draw on experience to learn how to become more effective predators. One of the best-documented examples of this comes from the shallow waters off Hawaii. Each year, from June to August, the Line Islands are invaded by some 14 million seabirds of 15 species that migrate to these isolated sand cays to nest and rear their young. Among the squawking, flapping, guano-excreting hoard are hundreds of thousands of pairs of the Black-Footed Albatross (Diomedea nigripes). Black-Footed Albatross chicks grow rapidly on a diet of regurgitated fish and, by about mid-June, most are preparing to leave the nest. Each morning, when the wind rises off the surrounding sea, these fledglings test their developing flying muscles. Some flap impotently, others rise vertically a few feet off the ground for a few seconds at a time, and still others glide a short distance to set down in the shallow waters surrounding the place of their birth. Just offshore, in water only a few feet deep, aggregations of Tiger Sharks (Galeocerdo cuvier) wait for them. Tiger Sharks are only seen here for the two weeks or so that the albatrosses fledge. Initially, the Tiger Sharks have little success capturing the hapless albatross fledglings that plunk into the shallows — the light-weight chicks are pushed away from the surface-rushing sharks like corks bobbing on a bow-wave. The sharks are out of practice, as many of them have not tried to catch albatross chicks since the same season a year before. After a few days’ of trial and error, however, the Tiger Sharks learn — or re-learn — the tricks essential to successful capture of the albatross chicks. The sharks learn that to ensure catching on of the bobbing birds, they must raise high out of the water. The sharks also learn that, if they miss a given chick, they are most likely to re-acquire it a short distance upwind — for that is where the panicked but weak bird will probably land. As we shall see in the next chapter, the White Shark also learns how to maximize its chances for predatory success.
Sharks earn their predatory living gliding through a complex, four-dimensional and dynamically changing liquid universe. Like its less infamous kin, the White Shark navigates from place to place in a visually concealing realm punctuated by acoustic, chemical, vibratory, and electrical signposts we do not yet know how to read. Until relatively recently, the comings and goings of the Great White and most other sharks were mysterious and completely unpredictable. But, thanks to the tireless efforts of hundreds of marine researchers, our near-total ignorance of shark movement patterns is slowly being replaced by the beginnings of an understanding.
Accumulated returns from shark tagging programs conducted since the mid-20th Century off the shores of many maritime countries have begun revealing basic patterns of seasonal migration in many species. More recently, sonic telemetry (the underwater equivalent of radio tagging) has elucidated the day-to-day movements of numerous species of sharks. These studies have revealed surprisingly well-defined and predictable patterns of movement for some shark species at certain locations. For example, off northern California and South Australia, sonic telemetry studies have shown that White Sharks move about in fairly regular and predictable patterns. Each autumn, from about August to November, White Sharks appear off the craggy and isolated Farallon Islands, California, apparently to prey upon the seals and sea lions that breed there. White Sharks in Spencer Gulf, South Australia patrol around and among the rocky islands in patterns that suggest the sharks form a resident population, each member with a discrete home range. At Rangiroa Atoll, French Polynesia, shark behaviorists Donald Nelson and Richard Johnson have found that sonically tagged Grey Reef Sharks (Carcharhinus amblyrhynchos) are astonishingly regular in their day-to-day movements. Johnson and Nelson found that these sharks’ movements are so regular that they could predict, down to a matter of minutes, when and in what direction an individual shark would pass by a given point along its established route.
How do sharks manage to keep such well maintained schedules of time and space? The seasonal and daily movement patterns of the Port Jackson Shark (Heterodontus portusjacksoni) have for decades been studied by Australian zoologist A. Ken O’Gower. O’Gower found that these chubby, bottom-dwelling sharks repeatedly visit specific resting sites on rocky reefs at South Bondi, New South Wales, and — when disturbed — move directly from one site to another. In addition, he found that Port Jackson Sharks also use specific resting sites in Sydney Harbor and — when transferred by boat to different localities within the Harbor, up to 1.9 miles (3 kilometres) away — returned to their original resting sites. This is no mean feat, as Port Jackson Sharks average only about 2 feet (60 centimeters) in length. Working with his long-time colleague, fellow Aussie zoologist Allan Nash, O’Gower had previously used tagging to demonstrate that Port Jackson Sharks migrate from as far south as Tasmania to Sydney Harbor to lay their auger-shaped eggs at specific, traditional sites. Based on these studies of precision navigation in the Port Jackson Shark, O’Gower proposed in a bold 1995 paper that this species must have a highly developed spatial memory.
Many species of sharks utilize specific bays or other sheltered areas for egg-laying or pupping and still others for mating. It is likely that the White Shark, too, seeks out specific locations for giving birth and mating, but these remain to be discovered. As a prelude to mating, many shark species perform complex — and sometimes violent — precopulatory rituals, often resulting in females of the species receiving nasty-looking but not life-threatening scars on their nape, back, flanks or fins. These sexual rituals are absolutely vital to securing the mutual understanding and cooperation that intromission demands.
As well-armed creatures capable of seriously injuring one another, sharks have evolved many other complex and subtle social rituals. We are only just beginning to understand how to read shark body language. Many of the most overt signals occur in competitive contexts, such as during feeding on highly localized bait or in approach-withdrawal conflict situations. In the course of my own field research, I have discovered that shark threat displays are most often elicited when a shark’s idiosphere (personal space) is persistently violated. I have also discovered that these so-called ‘agonistic displays’ vary from species to species, yet some common features of these displays are becoming clear. Observations of social interactions among White Sharks indicates that this species, too, has a complex and dynamic social life that is — for the most part — remarkably peaceful. White Shark social hierarchies are apparently relatively stable and peaceable: each member of a given population seems to understand its rank relative to the others, recalling which individuals are dominant over itself and which are submissive. When disputes over possession of a prey item or invasion of idiosphere occur, they are usually resolved non-violently through agonistic displays.
All of the foregoing strongly suggests that the mental universe of the White Shark is quite complex. Given its remarkable sensory talents, ability to examine, learn and remember, the strategic demands of predation and reproduction, the dynamic complexity of its social structure, and basic communicative ability, it is easy to appreciate why the Great White has evolved such a large, complex brain. What the White Shark does guided by that large, complex brain is a topic of much interest and debate. Much of that interest and debate has centered on the question of why the Great White sometimes bites, kills, or eats people (there’s no interest like self-interest). We feel confident that if only we understood why White Sharks attack people, we might be better able to protect ourselves. But to understand why the Great White occasionally attacks humans, we need to explore how this creature thinks — especially how it perceives, learns about, and reacts to human beings in its environment. Understanding this holds important implications for humans who find themselves in the company of this very powerful and well-armed shark.
Many people pride themselves on being intelligent, yet most have no clear idea of what they mean by that term. We recognize that there are different degrees of intelligence, ranging from moderate to extreme, although we find it very difficult to measure this quality in a way that everyone can agree upon. And most of us accept that, although clearly not as clever as ourselves, certain animals – such as dolphins, monkeys, octopuses, and at least some dogs – show signs of intelligence, whatever that is.
Defining intelligence is not easy. The challenge becomes particularly difficult if we attempt to define this elusive quality in a way that facilitates comparison across species boundaries. But if we are to tackle the question of White Shark intelligence, we must begin with at least a working definition of that slippery concept. I would suggest that, at its crux, ‘intelligence’ is the faculty of understanding the relationship between cause and effect. In practice, intelligence often involves making a choice from among several options by drawing upon experience to make judgments about likely consequences. The efficiency with which an animal can apply its past to shape its own future in ways desirable to itself is thus an index of intelligence. In evolutionary terms, the intelligence of animals can be measured and compared in terms of speed (how long it takes to make decisions) and adaptive fitness (the number of copies of an animal’s genes that survive into future generations as a result of the sum-total of its decisions). The faster and more adaptively an animal can make such decisions, the more intelligent it is.
As far as I know, this definition of intelligence is original with me. And although it may seem a fairly good attempt to define a complex and subtle concept in theory, it is extremely difficult to apply in practice. For example, not all decisions are of a simple either-or type; some are mind-bogglingly complex, involving the careful weighing of many factors and options before a decision likely to yield ‘desirable’ results can be reached. Therefore, comparing the number of units of time it takes an animal to arrive at decisions of different complexity – even assuming we can understand all of the parameters, sub-decisions, and implications involved – is all but meaningless. Further, it is extremely difficult to trace the reproductive consequences of a wild animal’s decisions. While it is fairly easy to trace human descendants and captive animals from virtually any pair of biological parents, this is much, much harder to do in the wild. It is conceivable that, sometime in the future, it may be possible to model all decisions as a series of binary options and to track the genetic legacy of any wild animal parent. But until such methodologies become available, my definition is not terribly helpful toward measuring the intelligence of the White Shark.
Fortunately, there are some generally agreed-upon correlates of intelligence that we can compare across species boundaries. Two physical correlates of intelligence are the relative size and complexity of the brain. Per unit of body mass, the White Shark has a rather small – but very differently-wired – brain compared with that of humans, and a medium-sized, moderately-developed brain compared with that of most sharks. Because we understand relatively little about how the physical structure of the brain affects decision-making processes, we cannot meaningfully compare the brains of sharks and humans, nor can we knowledgeably compare the decision-making mechanisms among various sharks.
The behavior of an animal is often the only indicator we have of what goes on in another creature’s mind. Unfortunately, like other sharks, the White Shark is very difficult to study in the wild. And since sharks generally behave oddly in captivity – and the White Shark, in particular, has never been successfully maintained in an aquarium for more than a few days – we have little more to go on that a few, scattered anecdotes. Yet those anecdotes are highly suggestive that the White Shark often behaves in ways that are, by my working definition, intelligent.
- underwater photographer Valerie Taylor described an incident in which a large White Shark off South Australia stopped feeding on the bait it had been enthusiastically consuming and swam over to a large metal drum that had fallen into the water, apparently to investigate it; the shark repeatedly nipped the bobbing drum in a way that suggests exploratory play
- abalone diver Jon Holcomb described an attack on him by a large White Shark, in which the shark nipped and shook his right arm and released it, bumped him three or four times in the chest with its nose, and then nipped, shook and released his left arm; until Holcomb struck the shark with his abalone iron, the animal’s investigation of him was surprisingly gentle and seems strangely systematic
- numerous reputable sport and commercial divers have noticed that White Sharks seem to be very aware of a diver’s eyes, and routinely approach from behind; this suggests a prudent caution in visually inspecting divers, which are large, noisy, and in many cases unfamiliar animals
- when testing a prototype of an electronic shark repellent in South Africa, Valerie Taylor noted that within a few hours, all the White Sharks lured to the area with bait became very wary of the research vessel, offered baits, and Valerie herself, having apparently learned that – in that particular context, at least – these formerly familiar objects often carried an unpleasant electric field
- researcher Scot Anderson has noted that the smaller, younger White Sharks at the South Farallon Islands often bump, mouth, and nip his research vessel, but the larger, older animals ignore the vessel, apparently having learned that the boat is neither food nor threat
- in the fatal attack on Theo Klein off South Africa, a White Shark insinuated itself between Klein’s body and a would-be rescuer riding a surf board; this suggest that the shark was protecting its ownership of a food resource by preventing access to it
- at Smitswinkle Bay, South Africa, whale biologist Peter Best reported as many a seven White Sharks apparently working in concert to move the carcass of a partially beached Pygmy Right Whale (Caprea marginata) into deeper water to facilitate feeding; if true, this incident suggests an impressive understanding of the basic properties of floating objects
So, what can we conclude about the ‘intelligence’ if the White Shark from reports such as these? Only that this species seems to possess curiosity and a sense of exploratory play, the ability to investigate novel objects in an apparently systematic way, a keen sense of caution and quickly learns to avoid unpleasant stimuli, it can learn to recognize inedible objects and not waste effort in trying to eat them, it has a sense of property and will defend a food resource in an oriented, apparently calculated – but non-violent – way, and may even co-operate to enable group members to maximize their feeding efficiency.
If I am interpreting these reports correctly, it is not hard to conceive how such responses could be adaptive. Balancing curiosity with caution seems a prudent means to increase the likelihood of surviving long enough to breed successfully. The ability to explore novel objects and to learn which are edible and which are potentially harmful may lead to a richer, more varied, and therefore more reliable diet. Because reproductive success in sharks is directly related to feeding success – with better fed individuals generally attaining maturity at an earlier age and having larger litters of bigger pups, which are themselves better able to survive than smaller pups – being better able to be feed and avoid danger can be expected to result in greater genetic representation in future generations.
So, is the White Shark ‘intelligent’? Based on the evidence available to me at present, I just don’t know. In its own way, it probably is. After all, White Sharks have been successfully making a living in the single largest interconnected living space on our planet for more than 10 million years. In contrast, our species has only been around for perhaps 1/100th as long – and in that time (among some very laudable and even noble achievements), we have been able to pollute our environment, devise ever more elaborate ways to save time that we don’t quite know what to do with, and repeatedly use our cleverness to cheat, abuse, or kill off one another at a profligate rate. Now I ask you: is that intelligent?
6) Cognitive Ecology:
Almost everyone who has shared a home with a pet has no doubt that at least some animals have recognizable emotions and motivations. For example, our dogs seem downright ecstatic to play or be reunited with us, our cats seem to pushily solicit and thoroughly enjoy being stroked at some times, demanding to be left alone at others. Yet, until quite recently, anthropomorphism was regarded as the cardinal sin of animal behavior. Attributing human-like motivations or mental states to animals was scrupulously avoided by ethologists, in the belief that doing so could lead to serious misinterpretations of why animals do the things they do. Within the past two decades, however, it has become more acceptable to credit animals with some manner of motivations and mental states that we had previously regarded as uniquely human. This change has granted us new ways to understand animal behavior.
One of the newest and most promising approaches to animal behavior is called cognitive ecology. Cognition may be defined as the neuronal processes through which animals acquire and make use of information. Ecology is the study of interactions between organisms and their surrounding environment, both living and non-living. Cognitive ecology represents a fusion of these two disciplines. Thus, cognitive ecology is concerned with how animals obtain information about the environment, relate it to themselves, and use it to survive. In practical terms, cognitive ecologists study the effects of information processing and decision making on animal reproductive success. The more efficiently an animal uses information from the environment to increase its genetic representation in future generations, the more adaptive are its cognitive abilities.
Various constraints limit a brain’s capacity to process information. As a finite structure, a brain has a sharply limited ability to handle information simultaneously. Therefore, an increase in the amount of information may decrease the quality of its processing by the brain and the competency of performing tasks based upon that information. For example, attention may be focused on a small portion of the visual field. A predator hunting for cryptic prey may maximize search efficiency by focusing on a single attribute, such as a specific color or shape. This attribute forms the basis of a ‘search image’. As a result of this strategy, however, a predator’s search rate is greatly reduced because only one type of prey can be scanned for at a time. Limited attention also restricts the capacity of an animal to simultaneously search for food and monitor predator activity. Animals cannot sustain high-quality information processing for extended periods. As a consequence, in relying on a search image to scan for food, performance of tasks such as vigilance may be greatly reduced in competence. This reduction in vigilance may, in turn, affect temporal patterns of activity and rest. For example, an animal’s foraging patterns may shift to suboptimal locations or times to reduce risk of predation. Inherent limitations of a brain’s information processing capabilities thus force all animals to make such compromises.
To a greater or lesser extent, the brains of all animals store experiences in the form of memories. There are two basic types of memory, working and long-term. Working memory relies on short-term storage of information to be used in the near future. A familiar example is temporarily committing a phone number to memory while one dials; in most cases, the number is lost from working memory by the time the phone is replaced in its cradle. Working memory typically has a very limited capacity, although perhaps — like humans — animals can learn to overcome this constraint. In contrast, long-term memory is generally regarded as being virtually unlimited. Long-term memory enables humans and other animals to store information over a protracted period, often years or even decades. Examples include remembering the name of a childhood playmate or the eye color of one’s grandmother. However, it is likely that maintaining memories is costly — especially the effort required preventing mingling of various items stored in memory. Most of us, for example, cannot faithfully recall our high school locker combination, as this once-useful information has become clouded through long disuse and replacement with bank account, social security, and various other numbers that plague our adult lives. This mingling of memories, combined with limited attention span, probably forces non-human animals to limit the number of experiences stored in long-term memory and to concentrate working memory on a single activity at a time.
Learning may be defined as the processes by which animals record experiences in memory and draw upon them to alter their responses to their environment. Not all forms of learning are equally complex. Simple forms of learning are effective as long as an identical behavioral response is a sufficient adaptation to some frequent environmental change. The processes by which animals learn that a given stimulus has no consequences for them are termed ‘habituation’. With repeated exposure to an inconsequential stimulus, responsiveness becomes greatly reduced and may disappear altogether. In contrast, complex learning is favored when feedback can be used to improve behavioral responses to subsequent occurrences of a given event. The processes by which animals learn to associate a signal with some event that will have some future impact on them are termed ‘conditioning’. A familiar example is Pavlov’s dogs salivating in response to a ringing bell, having learned that the sound indicates the imminent arrival of food. The most complex forms of learning demonstrate a clear understanding of cause-and-effect relationships. Some animals are able to learn that their own behavior can affect their environment – that their actions may bring about desirable events or preclude undesirable ones. Examples of events requiring complex learned responses include: foraging, predation, mate choice, parental care, and social interactions.
An animal’s learning capacity can be correlated with its longevity and level of social organization. Rich learning capacities rarely appear in short-lived or solitary species associated with such factors as long lifespan, hierarchical social structure, and parental care. These factors, in turn, seem to be correlated with large brain size. Further research is required to establish the neuronal foundations of cognitive constraints, particularly as they relate to an animal’s ecological role. However, there can be little doubt that the nascent field of cognitive ecology will provide new insights into the mental capabilities of many animals – including the White Shark.
7) Shark’s Brain Shaped Vagina (additional reference):
The shape of shark’s brain took similar identity to our women’s vagina. Obviously by studying female human biology of their womb and their functions can be strangely or oddly behaved. Generally speaking when women are going menstruation are often dangerous to most ocean fishes, its best to stay out of the water to prevent serious injuries to women or other predatory fishes. The function of matured and undeveloped vagina has mysterious questions still have with their doctors. Plus scientist came to a consensus there’s no chemistry among the functions or correlation too many behavior to unknown consequences, but because of the oddly functions that may function of vagina or sharks.
Original Format: Microsoft Word Document Psychology of Sharks (first copy) and Shark Mind (second copy)
Reference: Biology of Sharks and Rays Elasmobranch Research Organization “http://www.elasmo-research.org/” “http://www.elasmo-research.org/staff.htm” ReefQuest Centre for Shark Research Text and illustrations © R. Aidan Martin