Ecology
Sharks have earned a reputation as ruthless lonely predators, but scientists have recently discovered that certain species of these fish live in a very social environment, even starting long-term relationships and can interact with other individuals of their own species.
New studies, published in Animal Behaviour, have shown how one population of the Malgash nocturnal shark (pictured) organized three communities and two “subcommunities”. These studies have shown for the first time that adults of this shark can form stable and long-term social relationships.
You can often hear reports that these sharks pierce their sharp fangs into surfers and swimmers from time to time.
Johann Mourier, research leader, said that “other species, such as the dark-fin gray shark and the bronze hammerhead shark, form groups where each individual has its own place, and these fish species also have a complex social organization.”
Maurir, a scientist at the Center for Environmental Studies and colleagues, conducted research on Moorea Island, the “Society Islands” archipelago in the Pacific Ocean, French Polynesia. The researchers made seven dives to a depth of about 15 meters and photographed sharks.
After analyzing the data, they determined that sharks did not gather in groups randomly, but were able to organize themselves, and each individual group had a special social significance.
“The four main communities included individuals of different sexes who had separate sites. Moreover, individuals in these communities were more likely to “communicate” with members of the same sex and relatives of equal size,” Maurir said.
In previous studies, he determined that the length is proportional to the age of the shark, while Malgash nocturnal sharks become sexually mature at 7 years of age. At this age, they reach a length of just over 1 meter. Females of this shark species are slightly larger than males.
Maurir suspects that sharks are gathering in packs for protection and to avoid aggression towards each other. He and his colleagues noticed an interesting thing: a group of 4-5 sharks can gather a flock of fish near a coral reef while hunting. This suggests that predators are able to interact to make it easier for them to hunt.
Sharks are also likely to form groups in which each individual focuses on other members of the collective. Using individual territories, sharks help each other better understand environmental conditions.
The researchers noted that the brain's ratio to body weight of sharks is comparable to that of mammals, which indicates that they are capable of complex social behavior, as do birds and mammals.
Due to the fact that sharks are very mobile and difficult to observe on the high seas, the fact that they are able to build social ties has remained unknown to scientists until recently.
Another study led by Damian Chapman found that the spear-toothed lemon shark in Bimini, Bahamas, tries to stay on the coast line where it was born for a long time years.
“We were very surprised when we found that lemon sharks tend to live around the islands where they were born for more than half of their adult life,” said Chapman, a shark researcher at the Institute Stony Brook University Ocean Conservation.
Both studies found that age seems to help sharks build social relationships. Family ties are also likely to be quite important for sharks. Maurir and colleagues are currently exploring this possibility.
Scientists cut off fin pieces from 70 percent of sharks that participated in research to analyze their DNA. This will help to find out whether they form groups of relatives, as is the case with other social animals, such as some species of mammals.