A pair of orcas working in concert have been killing great whites along a stretch of South African coastline since at least 2017, plundering the sharks’ nutrient-rich livers and discarding the rest.

Scientists have been trying to make sense of the hunting approach, which has driven the sharks away from some parts of the coast around Cape Town, and now research has revealed a startling new twist in the behavior that could offer clues on what it might mean for the wider marine ecosystem.

Scientists witnessed one of the hunters, a male orca known as Starboard, single-handedly kill a 2.5-meter juvenile white shark within a two-minute time frame last year.

“Over two decades of annual visits to South Africa, I’ve observed the profound impact these killer whales have on the local white shark population. Seeing Starboard carry a white shark’s liver past our vessel is unforgettable,” said Dr. Primo Micarelli, a marine biologist at Italy’s Sharks Studies Center and the University of Siena who was aboard one of two vessels from which researchers observed the attack.

“Despite my awe for these predators, I’m increasingly concerned about the coastal marine ecology balance,” Micarelli said.

It’s not unprecedented for orcas, highly intelligent and social animals, to hunt large animals individually. However, it’s the first such occurrence involving what is one of the world’s largest predators — the great white shark — the researchers reported in a study published Friday in the African Journal of Marine Science.

Starboard’s kill is at odds with more widely observed cooperative hunting behavior among orcas, which can surround large prey, such as sea lions, seals and sharks, and use their combined intelligence and strength to attack, said lead author Alison Towner, a doctoral researcher at Rhodes University.

Previously observed attacks on great whites involved between two and six orcas and took up to two hours, according to the study.

The event detailed in the study took place on June 18, 2023, 800 meters offshore close to Seal Island near Mossel Bay — about 400 kilometers east of Cape Town — where people on two vessels were observing the orcas. Less than an hour after arriving, a shark appeared near the surface, and researchers, tourists and others on board witnessed Starboard grip the left pectoral fin of a shark and “thrust forward with the shark several times before eventually eviscerating it” in less than two minutes, the study said.

Later Starboard was photographed from one of the vessels with a “bloody piece of peach-colored liver in its mouth,” according to the study. (SD-Agencies)

Words to Learn 相关词汇

【一起】yīqǐ in concert together

【没有先例的】méiyǒu xiānlì de unprecedented never having happened or existed in the past

早自2017 年起，一对虎鲸就开始在南非的一段海岸线上合作猎杀大白鲨，掠食鲨鱼营养丰富的肝脏，然后将剩下的残躯丢弃。

科学家们一直在试图弄清它们的猎杀方式，因为虎鲸的存在已经迫使鲨鱼逃离开普敦周围的部分海域。现在，研究揭示了这种捕猎行为一个令人震惊的新变化，可能为更广泛的海洋生态系统变化提供了线索。

去年，科学家们亲眼目睹了其中一头名为“右舷”的雄性虎鲸在两分钟内单枪匹马地猎杀了一条 2.5米长的幼年白鲨。

意大利鲨鱼研究中心和锡耶纳大学的海洋生物学家普里莫•米卡雷利博士说： “二十多年来，我每年都去南非，观察虎鲸对当地白鲨数量的深远影响。看到“右舷”口衔着白鲨的肝脏从我们的船边经过，这景象令人难忘。”当时两只船上的人观察到了这次捕猎行为。

米卡雷利说：“尽管我对这些掠食者充满敬畏，但我越来越担心沿海海洋生态平衡的问题。”

虎鲸是一种高智商的社会性动物，单独捕食大型动物并非没有先例。然而，研究人员报告说，这是大白鲨首次被单枪匹马地猎杀，而大白鲨本身也是世界上最大的捕食者之一。这项研究在周五发表在《非洲海洋科学杂志》上。

研究第一作者、罗德斯大学博士研究员艾莉森•汤纳说，“右舷”的杀戮行为与虎鲸更常见的合作狩猎行为不符。虎鲸可以围猎大型动物，如海狮、海豹和鲨鱼，利用智慧和力量攻击猎物。

论文记述，此前观察到通常是两到六头虎鲸一起围猎大白鲨，整个过程耗时两小时之久。

研究详述的案例发生在2023年6月18日，距离开普敦以东约400公里的莫塞尔湾附近的海豹岛近海800米处，当时两艘船上的人正在观察虎鲸。

研究说，船只抵达不到一小时，一条鲨鱼出现在附近海面，研究人员、游客和船上的其他人目睹了“右舷”咬住鲨鱼的左胸鳍，并“推着鲨鱼向前行进了几次，最终将其撕碎”，时间不到两分钟。

研究报告称，“右舷”后来被一艘船上的人拍到“嘴里含着一块血淋淋的桃红色肝脏”。

(Translated by Debra)