Monday, 21 November 2011
As described in my former posting (below), the blackfin reef sharks (Carcharhinus melanopterus) I was able to study closely for many years, demonstrate that they know each other as individuals in a variety of ways, one of which is their tendency to travel with a preferred companion. This pattern of swimming with a companion may have facilitated their acceptance of me, permitting me to swim over long periods of time with different individuals and learn where they went and how they passed their days.
They spend much of their time in home ranges, familiar regions where they prefer to be. Such areas are not defended in the way that territories are, so sharks with overlapping home ranges know each other. When they travel, they often go with one or more of these “neighbours”. They follow circular paths hundreds of feet across, oriented in different directions so that from above, their path has the shape of figure eights or cloverleafs. Following such circling pathways, they repeatedly cross each others' scent trails and thus remain in loose contact while moving together, yet they are rarely within visual range of each other.
It became apparent through a variety of types of observations, that these sharks are accustomed to being in contact with others while remaining out of visual range.
Further, in a variety of situations they hid behind the limits of visibility to observe something without showing themselves. Sometimes, they came into view for a brief look, but other times they were capable of staying hidden for long periods, waiting, while I thought that they had left the area.
One illustration of this unexpected behaviour occurred during a period in which I was medicating a sick shark. Night after night I waited for him, holding his medicated food out of the water while encircled by a whirlwind of healthier sharks who wanted to get the treat instead. Each night I had to think up some new tactic to get the medicine to the sick one, because the others always seemed to be one step ahead of me.
Some of the sharks waited beyond visual range for me to throw the food, then zoomed in at top speed and snatched it the moment they heard it splash into the water, before the sick shark, or any others present, noticed what I had done.
Their actions indicate that they were concentrating on (observing) what I was doing from beyond the visual limit, and waiting in expectation for a signal that they knew. They were holding a mental representation of the signal in mind, with the intention of acting when it came.
On some days I travelled a long way looking for the sick shark. The rest of the group of fifteen to thirty sharks followed, remaining out of visual range until the right moment.
One juvenile shark always followed me from the moment I arrived in the lagoon until the moment I left, showing herself only about four times in the two hours I usually spent there, though I could check on her continuing presence beyond the veiling light, by ceasing to swim ahead, and waiting.
The sharks I knew always came straight up to my face when they saw me, in an apparent greeting gesture, while shy strangers waited out of sight, only briefly passing into view from time to time until they felt confident enough for closer approaches. Sometimes a shy shark would suddenly come from behind me for a close look. If I looked above the surface, that was when a curious shark would come up to me for a look or a sniff. They clearly used the knowledge of whether I could see them at a given moment opportunistically.
Once a lemon shark came early to a stormy evening session with my sharks, in which I was obliged to cling to my kayak to remain stable in the torrential current. He came and went as if I weren’t there, and it was easy to imagine that he had not seen me. He had been out of sight for fifteen minutes when I drifted away from the boat, whereon he immediately appeared, passing just within visible range to investigate the kayak. He had been aware of me, and keeping track of my location; he came to investigate my kayak as soon as he could do so while remaining out of sight.
Sharks are self-aware to the degree of being aware of being present and observable. Since any animal is a self-serving entity, seeking food for the self, protecting the self, saving the self, and so forth, it is logical that to be aware of the self, as distinct from others and the environment, would result in survival benefits. Thus, evolution, through natural selection, must favour self-awareness.
Much of our train of thought is automatic. We tend to think all the time, just as our hearts beat all the time. The predominant nature of thought in our subjective experience suggests that its roots are deep in our nervous system, and argues against the position that thinking is a recent evolutionary development. The way this automatic flow of thought tends to centre on the interests of the self, further supports the hypothesis that self-awareness and self-interest were selected for, and are likely primary in other species as well.
The originator of the scientific field of cognitive ethology, Donald R. Griffin (Animal Minds 2001), argued that when an animal hid itself from human view, it was demonstrating its awareness of itself.
He described how Lance A. Olsen had reported that grizzly bears sought places from which they could watch hunters while remaining hidden. Other observers had reported that bears tried to avoid leaving tracks. The researchers concluded that these bears were aware of being present and observable as well as creating effects―their tracks―through their movements, which could be seen by others.
The sharks’ habitual way of remaining concealed behind the veiling light until an opportunistic moment, or approaching from behind to avoid being seen, is in the same category.
(c) Ila France Porcher