(Screenshot / YouTube / Sea Search Research & Conservation)
A group of people captured on video for the first time how South African killer whales hunted white sharks.
The rare footage was taken in May this year from a helicopter and a drone.
According to zoologists, it was previously assumed that only two killer whales from South Africa, Port and Starboard males, learned to hunt white sharks.
However, new observations suggest that they passed on their skills to their congeners through social learning.
Killer whales (Orcinus orca) are among the most dangerous marine predators.
Their large size, high intelligence and ability to work in a team allow them to hunt different prey: fish, seabirds, pinnipeds, dolphins and even other whales.
Sometimes killer whales even attack white sharks (Carcharodon carcharias).
For example, a team of zoologists recently described how Port and Starboard male killer whales settled near Hansby (South African) and began to hunt white sharks for their energy-rich livers.
As a result, the sharks had to leave the region where they met regularly until recently.
Researchers have collected enough evidence that Port and Starboard prey on white sharks.
However, until April of this year, they did not observe this behavior in person or capture it on camera.
CAUGHT ON CAMERA
On May 16 at 3:30 pm, a local resident named Christiaan Stopforth spotted a group of five killer whales in the ocean near the town of Mosselby, and began filming them with a drone.
At first, all individuals kept together, but then Starbord and an unknown individual, which was given the code name KW2, separated from relatives KW3, KW4 and KW5.
He then headed for an area half a kilometer east of the mouth of the Hartenbos River.
While KW3 and KW4 remained on the surface, KW5 sank to the depths and soon returned, pushing out the muzzle and turning the three-meter white shark upside down.
The fish looked already dead. Once on the surface, KW5 inflicted a bite in the region of the pectoral fins, releasing a cloud of blood.
After that, the killer whale began to dive with the victim in its mouth, but then released it and swam away.
KW3 quickly swam up to the shark, grabbed the fish by the tail and disappeared under the water with it.
After some time, KW3 surfaced far from the shark's last sighting, and then all three killer whales headed west. Later, Starboard sailed there with KW2.
It was not possible to find the corpse of the shark, allegedly killed by KW5.
On the same day, around 2 pm, another local resident, Dudley Archer, flew several times over the mouth of the Hartenbos River in a helicopter.
He saw two killer whales in the sea, which killed two white sharks, but did not have time to capture them on video.
However, he was able to film interactions between four killer whales from the previous group, and several great white sharks on his smartphone.
The first video, taken at 2:07 pm, shows Starboard chasing a shark, while the second video, taken at 2:27 pm, shows another killer whale following another shark.
Both killer whales kept close to the victims and moved slowly, and the sharks tried to avoid the attack by swimming around the killer whales in circles.
Another video, recorded at 2:19 p.m., shows Starboard and three other killer whales floating near the surface.
Judging by the photos that were taken a few seconds before, the predators ate a large piece of shark liver.
Probably, killer whales kill sharks for the liver, which can provide energy for an adult for a day (it’s also easy to harvest because it floats), and the rest of the carcass is abandoned.
In total, killer whales killed two or three white sharks in 71 minutes of observations.
CHANGES IN THE ECOLOGY
When killer whales began to hunt white sharks in the vicinity of the city of Hansbay, the sharks soon left the place.
The same thing happened in the vicinity of Mosselbay.
Minutes before the start of Stopfort and Archer's observations, people on the coast saw white sharks rushing away from this area of the ocean.
Some individuals even swam in shallow water.
In addition, drone counts showed that almost no white sharks remained in the vicinity of Mosselbay after the attacks.
If before May 16, four individuals of this species were noted in less than an hour, then in the next 8 days only one was observed.
Tour operators who organize caged dives with white sharks also noted that they saw an average of 3.3 sharks per dive until May 16, but after that they disappeared for 45 days.
The next white shark was spotted here only during dives on the first of July.
The zoologist Alison Towner from Rhodes University's note that the ability to prey on sharks is more widespread among South African killer whales than they thought.
In a previous publication, the authors assumed that only the Port and Starboard use this type of hunting.
However, observations made last May suggest that white shark hunting skills are passed from one individual to another through social learning.
If a significant portion of the South African killer whale population learns to hunt white sharks, this will have serious consequences for the local ecosystem.
Source:
- Ecology: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.3875
- YouTube:
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