Most animals are afraid of humans, so they try to keep as far away as possible from their noisy, bright cities. But there are some species that don’t mind the presence of humans and have even learned to benefit from it.
When it comes to pigeons, from a human point of view it is rather harmless. The raccoon is different. Some find the animals, which are about half a meter long with the broad face and round ears, cute, others consider the omnivores, who like to clear out garbage cans, to be the worst pests of all.
In any case, the news from a team led by Neil Hammerschlag from the University of Miami is pretty scary, according to which some shark species also seek proximity to humans and swim purposefully in the direction of large cities. Even knowing that only about five people die each year as a result of shark attacks, is the result of the investigation just published in the science journal Marine Ecology Progress Series has been publishedrather worrying.
“There are few studies that have examined the movement patterns of predatory fish in relation to cities,” says Hammerschlag. “But because other studies have shown that terrestrial predators avoid cities, we expected that sharks would do the same.” But this assessment turned out to be wrong. “We were surprised that the sharks spent so much time near the lights and noise of the bustling city. They often stayed close to shore, no matter the time of day.”
For their study, the scientists caught, tagged and released 14 great hammerheads (Sphyrna mokarran), 13 bullsharks (Carcharhinus leucas) and 25 Atlantic nurse sharks (Ginglymostoma cirratum) off the Florida coast near the metropolitan city of Miami free. The transmitter was implanted in bull and nurse sharks. The researchers did not want to subject the stress-sensitive hammerhead sharks to this procedure; they therefore attached the transmitter externally to the animals’ back muscles. For five years – between 2015 and 2019 – the scientists tracked where the sharks were and when.
Two of the shark species studied are known to occasionally attack humans
The evaluation of the movement patterns showed that the predatory fish were more often than average in densely populated sections of coast. The researchers don’t know exactly why the animals seem to be looking to be close to humans. However, they suspect that the sharks are attracted to fish waste or that nutrients released into the sea with city sewage promote the proliferation of algae. This could proliferate fish that feed on these algae, which in turn could attract the sharks to eat the fish.
According to the authors of the study, this could be dangerous for both sharks and humans: “Because they spend so much time near the coast, there is a risk for the sharks that they will come into contact with environmental toxins and that they will be caught by fishermen.” , says Hammerschlag. “Both of these could affect their health and chances of survival.”
For people who bathe in the sea, the behavior of the animals means an increased risk of encountering a shark. Even though shark attacks are rare, the authors of the study believe that people should avoid going into the water in certain stretches of coast. After all, two of the species examined in the study are said to occasionally attack humans. Bull shark attacks can be deadly. in the International Shark Attack Filewhere shark attacks on people are recorded, attacks by great hammerhead sharks are also recorded, but fortunately never with a fatal outcome.