Over 8 months of observation, the researchers found five behaviors of sharks associated with feeding and not only.
Sharks have been roaming the world’s oceans for millions of years – as a rule, these powerful ancient creatures move only up and down the water column, but some of them have developed the skill of walking, writes Forbes.
Of course, sharks do not walk in the usual sense for us “on their feet”, for this they use their pectoral and pelvic fins. Most likely, you could even see footage of flying sharks literally running around the reefs of the Great Barrier Reef. These sharks became famous for their unusual walking skills after the release of a nature documentary.
Back in 2008, scientists believed that there were only five species of sharks in the world that had developed this unusual skill of walking on the seabed on their fins, but this year four more have become known.
In a new study led by Christian Parton of the University of Exeter’s Center for Ecology and Conservation, scientists have captured a unique video of nurse sharks (Ginglymostoma cirratum) walking on their fins while feeding.
In total, scientists conducted more than two hundred observations and used almost 80 cameras. As a result, they were able to identify and film 5 behaviors of nurse sharks, only one of which is not related to food.
Note that nurse sharks got their name from the sucking sound they make while feeding. Representatives of this species are distinguished by mottled skin, which is hard to miss among colored corals. As a rule, these marine inhabitants spend their days on the span, moving slowly along the sea days in search of prey.
In the course of their observations, the researchers noticed that nurse sharks often position their body above the food bait vertically with their heads down, as if they were standing on their heads. The second documented behavior was the nurse shark’s pectoral fin locomotion, where the animal significantly arched one or both pectoral fins and touched the seafloor with them. The researchers speculate that this allows the sharks to use the resistance of the seafloor to better maneuver their bodies. By the way, scientists also noticed that this behavior preceded the standard horizontal feeding of sharks.
The fourth behavior the researchers noted was that in the supine position, the shark seemed to tumble as it rolled onto its back to feed. But the fifth behavior that the scientists found was not at all related to feeding – the sharks simply walked past food baits and cameras.
Parton says he and his colleagues found that stationary horizontal feeding was three times more common in coastal waters compared to reefs. The researchers speculate that such feeding does not seem to require much energy, which is why it is so common.
At the same time, the authors of the study believe that such diverse feeding behavior can greatly contribute to the long-term conservation and distribution of this species in tropical and subtropical habitats.
Despite the fact that nurse sharks skillfully move their fins, this skill is still not developed in them in the same way as in other members of the plasmogill family, for example, bamboo sharks, narkins, or smooth skates. Scientists speculate that nurse sharks evolved this skill to gain an advantage while foraging in a dynamic environment.