Sharks were previously thought to lead solitary lives and have little contact with their own kind, but according to a new study, sand tiger sharks may in fact be quite social.
Sand tiger sharks (Carcharias taurus), also known as spotted ragged-tooth sharks, grey nurse sharks, ground sharks, slender-tooth sharks or blue-nurse sand tigers, are a shark species that inhabits coastline waters in the Mediterranean, eastern and western Atlantic, and near Japan and; they also swim in the waters of Japan, Australia, South Africa.
The sand tiger shark can grow up to about ten feet (approximately three metres) in length. They have a bulky body and a sharp, pointy head. The animals are grey and have reddish-brown spots on their backs. They usually feed on fish, skates, crustaceans, squid, and other smaller sharks.
The sharks that swim off the eastern coast of the United States usually migrate to Delaware Bay during the summer. Until recently, scientists were unsure whether the sand tiger sharks interacted socially, or closed contact with one another when they went back to the open ocean.
Previous researches have also investigated shark interactions. However, they were conducted in controlled environments, such as laboratories or pens. The new study is the first to ever observe social behaviour among sand tiger sharks that swim in the open ocean, the researchers said.
For the study – presented on Monday (Feb. 22) at the 2016 Ocean Sciences Meeting, and then published online – the researchers tracked the movements of sand tiger sharks by attaching acoustic tags to more than three hundred individual sharks. They also recorded the animals’ interactions for almost a year.
The results showed that the sand tiger sharks enjoyed social interactions year-round. By analysing data from two individual sharks, the researchers also found that the animals had almost two hundred interactions with another sand tiger shark. Moreover, they interacted more than once with the same individuals, according to the researchers.
Danielle Haulsee, one of the researchers and a doctoral candidate in oceanography at the University of Delaware in Lewes, said that in early spring and late winter, the sand tiger sharks hardy encountered any other shark and they were also not as social as in other months. It is possible that sand tiger sharks self-regulate their time spent in a group, according to Haulsee. Certain activities – like finding food – are best done alone. The ability of sand tiger sharks to make decisions regarding social networking casts is evidence that these animals are exactly ‘loners’ and do not always lead solitary lives, the researchers explained.
Overall, the new study also shows that social behaviour in animals other than mammals should not be ruled out by the scientific community, Haulsee said.
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