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Orcs that break up large white sharks are opening up in South Africa, a new study says

Orcs that break up large white sharks are opening up in South Africa, a new study says
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The Great Whites dominated an area of ‚Äč‚Äčabout 100 kilometers (62 miles) off the coast of Gansbaai. To the east of Cape Town, but in recent years they have been avoided to an article published in a journal African Journal of Marine Sciences On Wednesday.

The Gansbaai coast was once a popular destination for large white sharks, but observations have declined significantly in recent years. The study used long-term observations and labeling data to demonstrate that large whites were chased by orcas, sometimes known as killer whales.

Researchers also found the bodies of five large white sharks washed ashore, four of which had their food-rich livers removed. and one whose heart is removed. Researchers say they all had wounds opened by the same pair of orcs, and these wounds are more likely to kill larger whites.

The study tracked 14 large nets over a five-and-a-half-year period and found that when the orcs were there, they fled the area. Researchers believe that the fear of sharks causes a rapid, long-term mass migration when they know that a predator is present.

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“First, the individual large white shark did not appear for weeks or months after the orca attack in Gansbaai,” said Alison Tauner, chief white shark biologist at Dyer Island Conservation Trust, the study’s lead author. news release.

Tauner believes this is a “large-scale escape” similar to the wild dogs in the Serengeti fleeing certain areas when there are lions.

“The more often the orcs visit these sites, the farther away the large white sharks are,” he said.

A changing ecosystem

Before Orcas began to attack the great whites, the shark was absent from Gansbaai for a week in 2007 and three weeks in 2016.

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This means that the long breaks that research is witnessing are unprecedented, and this is changing the ecosystem in the area.

The bronze whale shark emerged as a new medium-sized predator in the region, Tauner said.

“Bronze whales are also attacked by orcs that show a level of experience and skill in hunting large sharks,” Tauner said, adding that nose fur seals hunt endangered African penguins.

“It’s a top-down effect, we have bottom-up trophic pressures from the widespread removal of abalone grazing in algae forests where all of these species are interconnected,” he said.

“Simply put, while this is still a hypothesis, there is a lot of pressure that the ecosystem can exert, and the impact of shark-eating orcs could be much larger.”

‘Sudden descent’

Tauner also believes that orcs are becoming more common off the coast of South Africa, and that this particular pair may be part of a group of rare shark eaters.

“This change in the behavior of both upper predators may be due to a decrease in predator populations, including fish and sharks, which may lead to changes in their distribution pattern,” he said.

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He said orcs focus on young sharks, which can have a greater impact on sensitive large white populations as the sharks grow slowly and mature at a late age.

The researchers acknowledge that sea surface temperatures may also affect the appearance of large whites, but “the immediate and sharp decline in observations in early 2017 and the long and increasing periods of absence cannot be explained.”

Other explanations may include a reduction in the number of predators due to direct fishing or fishing for large whites, but this is “unlikely to explain the sudden localized decline, although it may potentially contribute to the overall decline in large whites in South Africa.”

Another study in 2016 found that the number of large white sharks in South Africa was higher than previously estimated at several thousand.

In addition, DNA analysis of shark tissue has shown that the genetic diversity of South African whites is very low, making them more susceptible to external shocks such as disease or environmental changes.

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