Orcas, also known as killer whales, are powerful, intelligent predators. As the largest members of the oceanic dolphin family, they have a diverse diet and adapt to various ocean habitats, from polar regions to tropical seas. Their sophisticated hunting strategies and social cooperation make them apex predators. While their diet includes marine mammals, fish, and cephalopods, their interactions with other large predators, particularly sharks, have drawn scientific interest.
Confirmed Predation and Targeted Species
Orcas have been observed hunting and killing sharks, a behavior increasingly documented in various marine regions. In South Africa, specific orcas have preyed on great white sharks since at least 2017. This predation also extends to other large shark species, including mako and thresher sharks, and in the Gulf of California, bull and blacktip sharks. Observations are increasing, with instances recorded between 2022 and 2023 in areas like Cabo Pulmo National Park. While often a coordinated group effort, a lone orca named Starboard recently killed a great white shark in Mossel Bay, South Africa, in under two minutes, showing individual prowess.
Advanced Hunting Strategies
Orcas employ sophisticated, coordinated hunting techniques to subdue sharks. One common strategy involves herding, where a pod works together to corral prey. They use powerful tail slaps to stun sharks, disorienting them and making them easier to control. Body slams are also used to incapacitate sharks.
A precise maneuver involves flipping the shark onto its back, inducing tonic immobility. In this state, the shark becomes paralyzed and unable to move voluntarily, allowing orcas to access specific parts of the shark. This teamwork and intelligence allow orcas to overcome even large shark species.
The Nutritional Drive: Why Orcas Target Shark Livers
The primary motivation for orcas targeting sharks is the high nutritional value of their livers. Shark livers are calorie-dense, packed with fats and oils, providing a significant energy source. They also contain a high concentration of squalene, an organic compound aiding in buoyancy control and overall health.
This dietary preference drives their hunting behavior, leading to the precise removal of this organ. Orcas extract the liver with surgical precision, often leaving the rest of the shark’s carcass largely intact. This targeted consumption provides the substantial caloric intake needed to maintain their high metabolic rates and energy-intensive lifestyle.
Ecological Ripple Effects
Orca predation on shark populations can have significant ripple effects throughout the marine ecosystem. Observed changes include sharks abandoning traditional feeding grounds or migration routes. For example, great white sharks have been observed fleeing areas like False Bay, South Africa, when orcas are present, leading to their prolonged absence from these former aggregation sites.
This localized decline in shark numbers can initiate trophic cascades, where changes at the top of the food web propagate downwards. With fewer sharks, populations of their typical prey, such as Cape fur seals, can increase, leading to a reduction in fish populations. Other shark species, like bronze whaler or broadnose sevengill sharks, may also move into areas previously dominated by great whites, altering competitive dynamics and marine food webs.