Carcharodon carcharias , the great white shark, beloved / hated super predator. Hated only out of ignorance sensu stricto , loved by all those who instinctively undergo the charm of power and spectacle. Some of the greatest admirers are marine biologists, who dedicate their expertise and research effort to the white shark.
I study
A group of scholars, belonging to various institutions, including the DiBEST of the University of Calabria, the Aquarium Mondomarino of Massa Marittima and the Department of Biology of the University of Trieste have dedicated several years of studies to observe the behavior on the surface and the social interactions of the white shark, in the presence of passive prey.
The picture that emerges is far from the commonly diffused and distorted image of this animal as a sleepless and strenuous solitary predator.
The ethograms drawn by the researchers show well-defined, fairly predictable and repeated patterns in response to the stimuli provided. In particular, those linked to social interactions have a meaning also linked to the logic of dominance.
The research was conducted between 2000 and 2008 in the South African waters around the island of Dyer Island, aboard a specially prepared boat and a special semi-floating cage. Sharks, attracted by the groundbait released into the sea and habitual frequenters of these waters, were then observed, their sex and age (adult / immature) determined, useful information to subsequently trace the ethograms.
Different behavioral patterns have been identified in the interactions between two individuals at a time, such as swimming paired, giving precedence and following one of the two, swimming one above the other or hitting the tail on the surface that generate splashes of water. .
These behaviors were observed indifferently between the two sexes, while there was a strong correlation with the size of the animal
Sharks tended to exhibit one or more of these behaviors only if they were of similar size. A possible explanation for these data can come from the following hypothesis: in the presence of a prey two sharks of clearly different sizes have a clear dominance pattern for access to food, while if two sharks of similar size approach the same prey, it will be necessary to establish through behaviors that are not unnecessarily harmful which of the two will have the right to access the prey first.
Overlapping and paired swimming, as well as being dominant can also have implications in courtship. However, these are interactions with a strong visual component and this result is in evolutionary convergence with other phylogenetically very distant animals, such as cetaceans.
Regarding the behavior on the surface of individuals in response to the presence of passive prey (silhouettes), the behavior seems to follow an ethogram in which initially the shark slowly swims on the surface and in proximity of the prey and then carries out a series of inspection behaviors, in sequence and in variable number among the following: follows the prey, observes it closely, keeping still in a vertical position, or immediately under the surface, almost on the water. Not as frequently has been observed the Breach , the powerful attack from below, sudden and lethal, usually observed with prey such as seals and sea lions.
In some cases, a behavior called Spy Hop has been observed, in which the individual emerges vertically from the water with the whole head, and remains in this position for a few seconds (from 2 to 6) and then returns to the water.
It is worth mentioning that this behavior is in evolutionary convergence with the same behavior shown by cetaceans, especially dolphins, which however emerge almost half of their length, in balance thanks to the swimming movement of the tail.
Breaching behaviors and tail strikes on the surface have been observed mainly in males, and could have a competitive significance, affirming one’s presence.
As for the patterns of approach to the prey, it can be said that it is never a question of blind attacks, of univocal and disorganized behaviors. Conversely, patterns can vary and exhibit remarkable plasticity in response to the conditions present at the time. This data in particular must give food for thought when it comes to attacks on humans.
The research team’s studies did not stop at 2008, new data are collected every year and study methods are also implemented, for example by integrating observations from below with those from above, through the use of an aerial drone. recently used, which certainly provides a broader perspective than the boat. Each study that once again demonstrates how misunderstood sharks are opens a new window of knowledge, useful for debunking and reversing the bad name we’ve created for them.
