Dear colleagues and friends,
Having addressed the fascinating topic of the behavior of colossal marine mammals, today, an esteemed colleague shares this article published on March 1, 2024 by Taylor and Francis, published in the Plants & Animals section of PHYS.ORG and finally translated by us for this space. Let's see what they tell us about it...
“The amazing predation that occurred recently off the coast of Mossel Bay, South Africa, represents unprecedented behavior that underlines the orca's exceptional ability,” says Dr. Alison Towner, a researcher at Rhodes University (RU), who leads an international research team on these events.
The findings were published in the African Journal of Marine Science.
This recent information is the latest released by Dr. Towner and her team, who, in 2022, in the same scientific journal, revealed that a pair of orcas had been hunting and killing great white sharks off the coast of South Africa since 2017, managing to drive away a large number of white sharks from their natural hunting sites.
Orcas are generally known to work together to capture large prey such as sea lions, seals and even other whales and, of course, sharks as well. By hunting together, they can surround their prey and use their combined intelligence and strength to attack.
They can hunt large animals individually. However, this is the first case of its kind in one of the world's largest predators: the great white shark.
“Once again, as before in South Africa, killer whales show a strong preference for extracting and consuming white sharks' lipid-rich livers, a specialized feeding behavior,” explains Dr. Towner, who has studied great white sharks for the past 17 years, learning about their movement patterns through labeling data.
“But what we witnessed was an orca, nicknamed Starboard, due to its collapsed dorsal fin, acting alone to incapacitate and consume a white shark in an astounding two-minute period.
“Starboard was observed preying on a 2.5-meter (8.2 ft) juvenile white shark, and then carrying the shark's liver in its mouth beyond and beyond a vessel from which it was being observed.
“This sighting revealed evidence of solitary hunting by at least one orca, challenging conventional cooperative hunting behaviors known in the region.
“These are innovative insights into the predatory behavior of this species, and our findings contribute significantly to the global understanding of orca predation dynamics, improving knowledge of marine ecosystems and predator-prey relationships.”
During the observed interactions of this event, at least two white sharks died, as evidenced by the discovery of a second corpse measuring 3.55 meters (11.6 feet) nearby.
“The study raises critical questions about the impact of killer whale predation on shark populations in South Africa,” says Dr. Towner. “The displacement of several shark species due to the presence of orcas may have implications for the release of mesopredators and possible trophic changes in the marine ecosystem.”
Understanding the ecological dynamics of killer whale predation is critical to marine conservation efforts. The authors state that this event “underscores the urgent need for adaptable conservation strategies and vigilant ecological monitoring in the midst of changing environmental conditions.”
Dr. Simon Elwen, founding director and chief scientist of Sea Search Research & Conservation and the BotZoo Department at the University of Stellenbosch, is an expert in whale ecology, behavior and conservation status.
Commenting on the importance of Dr. Towner's team's findings, he says: “The observations reported here add more layers to the fascinating story of these two orcas and their capabilities. As superior and intelligent predators, killer whales can quickly learn new hunting techniques on their own or from others, so monitoring and understanding the behaviors used here and by other killer whales in South Africa is an important part of helping us understand more about these animals.”
The participation of terrestrial observers, tourists on boats and collaborating institutions played a “fundamental role” in capturing these crucial data and images of predation events.
This particular event “highlights the benefits of citizen science as a collaborative effort between researchers, tourists and organizations,” say the authors.
Esther Jacobs, from the Keep Fin Alive marine conservation initiative, recounts her experience witnessing predation: “Upon arriving at Seal Island in Mossel Bay, the smell of shark liver oil and a noticeable stain indicated a recent death. Seaport and starboard tracks near the island remained separate.
“Seeing a white shark's fin break the surface initially generated excitement, but that turned into a grim understanding when Starboard quickly approached. The moment Starboard quickly took advantage of my favorite shark species was devastating and intensely powerful.”
Co-author Dr. Primo Micarelli, from the Shark Studies Center and Siena University, was aboard the White Shark Africa ship and said, “During two decades of annual visits to South Africa, I have observed the profound impact that these orcas have on the local white shark population. Watching Starboard carry the liver of a white shark passing by our ship is unforgettable.
“Despite my fear of these predators, I am increasingly concerned about the balance of coastal marine ecology.”
To conclude, Dr. Towner highlights that the new findings on killer whales provide important additional information about how adaptable mammal predators specialize and diverge ecologically.
“The presence of these shark-hunting orcas is possibly related to a larger ecosystem dynamic. The rapid advances in this phenomenon make it difficult for science to keep pace with events, leading us to publish these brief timely communications.”
