Five species of sharks chose not to intersect while hunting and began to eat at different times of the day

Five species of sharks chose not to intersect while hunting and began to eat at different times of the day
Five species of sharks chose not to intersect while hunting and began to eat at different times of the day
Anonim

Marine biologists have found that different types of sharks go hunting at different times of the day. Scientists attached accelerometers to their dorsal fins and tracked when these animals were most active. It turned out that the tiger shark - one of the largest modern sharks - forages in the middle of the day, while the rest of the sharks have adapted to hunt in the morning, evening or night. The research is published in Proceedings of the Royal Society B: Biological Sciences.

To survive, competing species of animals need to occupy their ecological niche. Predators, for example, catch different prey or hunt in different territories. Many species have adapted to this evolutionarily: they have acquired jaws suitable for certain prey, or they have adapted biological rhythms for night hunting. In the last decade, scientists have understood how the hunting time is divided between different land animals, for example, large African predators, but when studying marine ecosystems, attention was paid more to the division of predators by territory and type of prey. Perhaps this is due to the fact that it is difficult to track the movements of highly mobile aquatic predators.

Biologists from Australia and the USA, led by Adrian C. Gleiss, decided to look at what time of day different shark species hunt. They caught 172 sharks of six species in the Gulf of Mexico: 21 blacktip sharks (Carcharhinus limbatus), 11 blunt sharks (Carcharhinus leucas), 71 gray-blue sharks (Carcharhinus plumbeus), 39 tiger sharks (Galeocerdo cuvier), 15 giant hammerhead sharks Sphyrna mokarran) and 15 bronze hammerhead sharks (Sphyrna lewini). All of these shark species are hunted during the winter months in the Gulf of Mexico, so they must compete for prey. The animals were fitted with accelerometers on their dorsal fins and then released back into the Gulf of Mexico. Accelerometer data were used to calculate the time of peak activity in sharks, which corresponds to the hunting period. In total, scientists analyzed 3776 hours of shark activity.

Biologists have found that different types of sharks hunt at different times. For example, one of the largest modern sharks - the tiger - hunts in the middle of the day, while the rest of the sharks have other periods. Blunt sharks forage in the morning hours, blue-gray sharks in the afternoon, and blacktip sharks even later in the evening. Hammerhead sharks (Sphyrna mokarran and Sphyrna lewini) hunt at night.

Distribution of hunting time in different shark species

The data obtained turned out to be unexpected for scientists: before that it was believed that all types of sharks hunt mainly at dawn and at dusk. The study demonstrated for the first time the distribution of hunting time during the day between different sharks, which helps them to exist in the same ecosystem.

This is not the first time sharks living in the Gulf of Mexico have been studied. Recently, American biologists have studied the behavior of small-headed hammerfish and realized that they are able to sense the Earth's magnetic field and are guided by the "magnetic map".

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