Long term study of the behaviour of individual sharks has shown that they are not just acting on instinct. Not only
are they thinking and highly intelligent—they are likely conscious too. So here is a review of how their actions reveal some of their mental states.
Occasionally reef sharks would flip on their backs to wriggle in the sand, presumably to scratch or to free themselves of parasites. On other occasions, a shark would turn to whip the side of its body against a sand bank. The floor of the lagoon was
made up of sand interspersed with reef flats and coral, and the sharks invariably chose only sandy places for such manoeuvres.
Sometimes a shark carefully positioned himself to use a smooth, flat surface of dead coral on which to rub himself. Apparently, he had intentionally surveyed the environment and chosen a suitable structure to use. He must have held
a mental image in mind of what he wanted, and referred to it while looking for a formation of the right shape.
Though this may not seem to be very impressive in terms of thinking in sharks, the availability of surfaces to use in this way does not mean that the animal will realize how they can be of benefit. For example, mynah birds (Acridotheres tristis), and
junglefowl (Gallus gallus), the wild ancestor of domestic chickens, both spend much of their time foraging for insects on the ground, and both have strong feet for walking. However, mynah birds have not discovered that they can use their feet to help them
uncover these insects, while junglefowl do so instinctively.
I was lucky to witness a clear decision
made by two sharks, between two possible choices. One day near my study area, I saw the fins of many sharks slicing the surface, and found a spawning event underwater. Sharks were gliding among the clouds of dancing fish, occasionally snapping one up. Two
blackfins came over when they saw me, and returned from time to time to circle me over a fifteen minute period. When I left and travelled another kilometre into the lagoon in my kayak, these two sharks followed from the spawning site.
They decided to follow me even though they had not seen me for several months, and they made the choice that was based on a
mental reference—a thought or memory—that sometimes I brought food. Yet, they were already in a situation in which they could see, hear, and smell food, moving in a stimulating way, and I had not fed them in that location before. This decision
to leave, based on a memory many months old, indicated that they must have made such memories, and referred to them, a clear act of cognition that indicates consciousness.
not see evidence of communication between sharks except through body language. Yet occasionally, companions acted in concert, leaving the other sharks, and swimming in formation to perform a specific act together. How they communicated the decision to do this
was not clear, but likely body language played a role.
In his book, The Secret Life of Sharks, Professor Peter Klimley described how great white sharks ritualize their conflict when a seal that one of them has killed comes under dispute. Each slaps the water at an angle
with its tail, and the shark who raises the most water and blasts it farthest wins the prey. For this ritual to be effective, each shark must view its opponent’s gesture as a communication, and understand it, since the winner gets the seal without a
fight, which could badly hurt both sharks.
Sharks often passed the same place at the same time repeatedly. One young visiting male passed by my observation post about five
meters to the right, between ten and fifteen minutes after sunset each night for several weeks. Each time, he saw me and came for a closer look, then turned and went on his way.
Another rare visitor’s first four visits, though months apart, occurred precisely at the moment that the sun touched the horizon, four days before the dark of the moon.
Intrigued, when one of the residents who had habitually met me on my arrival in the lagoon, began coming instead at the end
of the feeding session and missing out on the food, I kept careful track of the time of her return. For reasons known only to her, she had suddenly begun to spend her days in the ocean. Over a period of many months, she returned about ten minutes before sunset,
night after night. Sometimes, she still met me when I arrived at the study site, yet other times, I saw her return from the sea when it was nearly dark and pass in the distance without coming to the feeding session.
Besides illustrating a remarkable ability to follow a daily schedule, and yet be flexible about it, her actions indicated that she had not become
dependent on my weekly feeding sessions, though she had known about them since she had been a juvenile.
sharks seemed to have no trouble catching a fish when they wished to, and often came to the feeding sessions only to socialize. Resident sharks routinely left for months at a time, and visitors did not remain in the area because of the food. Though many came
to my feeding site at the proper time, their long-term schedules were unaffected by the few scraps I provided once a week to facilitate my observations.
The resident sharks learned
in time that the fish-scraps I brought to the feeding sessions were in the back of my kayak. Though this species has not been documented breaching the surface to eat or to look around, these sharks found that the food could be accessed by leaping from the
water, and leaning towards the boat, while snapping at whatever they could locate. The sound of their jaws snapping shut made loud clapping sounds, and some of the kayak’s straps were cut, punctured and sliced by their sharp little teeth.
This behaviour pattern was a new foraging technique they had discovered, that was initiated by one or two sharks and instantaneously
copied by the others present. They used it from then on. This discovery happened twice, in different locations, under different circumstances, with different groups of sharks, and is an example of social learning, which is basic to the development of culture.
Under normal circumstances, the space above the surface is not something that these sharks would have reason to consider. But
they were presented with an artificial situation in which I came from above the surface and returned there, and so did the food in which they were interested. They would doubtless have stored memories about the surface from the occasions, particularly when
they were small, when they swam through it or up against it while chasing a fish, though it is unlikely they could have formed more than a vague impression that there was a space above, from such brief events. Yet, their behaviour suggested that they were
aware of a volume above the surface in which things could exist, and from which I came and went.
question in cognition is whether an animal knows that something continues to exist when he or she can no longer see it. An object apparently ceases to exist for dogs, for example, when it disappears from view. So few people would agree that sharks could understand
that I was in my kayak, even when I had just left their company and climbed into it. Yet they were aware. Indeed, the many ways that sharks took advantage of the opportunity to hide beyond visual range, strongly suggests that they understood very well the
idea that something continues to exist, in spite of being out of their view.
Sharks have exquisitely coordinated senses, and their behaviour indicated that they used this sensory input alertly to make
moment-to-moment decisions, and respond flexibly and appropriately to changing circumstances. They remembered the events in their lives, and referred to these memories in decision making. They were curious, but cautious, and learned quickly. Their versatile
behaviour, individual differences, and different ways of handling various circumstances, were not indicative of a set of stimulus / response reactions.
I have observed sharks underwater in the Bahamas, including bull and tiger sharks, and found that their behaviour was remarkably similar to the behaviour of the requiem sharks I had known in Polynesia. This is to be
expected since sharks have been evolving for four hundred twenty million years, and many species travel widely and are found around the globe. The essential qualities that sharks evolved to be so successful would already have developed in the ancestral forms,
before they evolved into modern species occupying the ecological niches we know today.
fish may seem primitive when looking down on them from the altitude of Homo sapiens, in fact they are highly complex and evolved life forms. And no brain is simple, as
anyone who has observed the activities of a spider will appreciate.
Ila France Porcher, Shark Behaviour
Specialist and SEI Board member, author of The True Nature of Sharks.