A killer whale-killing party is raging in South African waters.
A pair of men from 2017 orcas (Orcinus orca) cut at least eight large white shark (Carcharodon carcharias) Near the coast of Gansbaai, tearing and dreading terrible fish they eat their livers except in one case. Some of the sharks that scientists have occasionally found dead and broken on nearby beaches have even lost their hearts.
From small fish to large sharks, sea lions, etc. even blue whales. The authors of a new study, published on Wednesday (June 29), say that the violent escapes of two separate whales rarely have such a clear and immediate effect on their habitat. African Journal of Marine Sciences.
According to researchers, after the two-serial killer cetacean began to go crazy five years ago, the number of large white sharks in the area has sharply decreased. Using a combination of long-term observations and labeling data, the researchers found that dozens of sharks were actively fleeing areas along the Gansbaai coast when orcs were nearby. Tagged sharks sometimes disappear for weeks or months, leaving areas historically dominated by large whites.
“What we are witnessing is a large-scale escape strategy that reflects the use of wild dogs in the Serengeti region of Tanzania,” said Alison Tauner, a senior biologist who has studied white sharks. the statement said. “The more often the orcs visit these sites, the farther away the large white sharks go.”
serial killer whales
Gansbaai is located about 75 miles (120 km) east of Cape Town. According to the authors of the study, the presence of large white sharks in the area throughout the year has made Gansbaai a popular tourist destination for shark watchers.
Reaching 16 feet (4.9 meters) in length and sporting several rows of up to 300 toothed, knife-like teeth, the great white is one of the best predators in the water. But since 2015, the Gansbaai shark has encountered a pair of adult male orcs landing on the beach.
Like the criminals in the cartoon, the orcs could be easily identified by traces of battle; the dorsal fin of one of the whales was bent to the right and the other to the left. These features inspired local whale watchers to give the orcas the nicknames Port and Sanjag. As whale observers saw the duo in Gansbaai, a large white shark washed the dead on the beach.
Between 2016 and 2017, five more white sharks were found dead – four of them with open bodies and torn livers. (Unlike bony fish, one in sharks very large, fatty liver, can provide a lot of energy and nutrients to attackers, Live Science has previously stated). The death of each shark coincided with the landscapes of Liman and Sancak in the area. Although their official death toll is eight, more undiscovered shark carcasses have disappeared into the sea.
In the six months since the death of the first shark, daily shark observations in Gansbaai fell to just one out of more than six per day. The detection of sharks marked with electronic sensors has also decreased. Prior to the 2017 attacks, sharks marked between three and eight were found in the area each day. A few months later, the figure dropped to zero. Transmitter data showed that individual sharks sometimes swam hundreds of miles away from Gansbaai within days of the orca attack. In some cases, the shark stayed away for six months or more before returning.
According to researchers, this massive shark migration has had a downstream effect on the local ecosystem. The most noticeable new medium-sized predatory bronze whale shark (Carcharhinus brachyurus) moved to the area to capture the place previously occupied by the great whites. According to researchers, this shark is often hunted by large whites, but with the departure of adults, the number of observations of bronze whales has increased significantly. The team added that this change could put pressure on the entire ecosystem by downsizing the entire food chain.
What is the primary cause of this killer whale whim? Researchers, no matter how severe, do not usually hunt large white sharks, but scientists have observed a rare subspecies of killer whales that specialize in shark hunting in South Africa. The team writes that Port and Starboard belong to this group. The sudden appearance of orcs in Gansbaai “may be due to a decline in predatory populations, including fish and sharks, which will lead to changes in their distribution pattern,” Towner said.
Additional observations of Gansbaai whales and sharks are needed to fully solve the mystery of this oceanic killing.
First published in Live Science.