Mental Processes of the White Shark
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.