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Sixgill shark carcass, its liver ‘surgically removed’ by orcas (Photo: Christine Wessels/MarineDynamics)
In the waters off the coast of South Africa, two orcas were recently observed engaging in a remarkable feat: they hunted and killed 19 sharks in just one day. The orcas not only killed the sharks, but they also ate their livers and left the rest of the carcasses to rot.
This behavior is extremely rare and has left many researchers and marine biologists scratching their heads. What could be behind this unprecedented attack?
Orcas, also known as killer whales, are apex predators that can be found in all of the world's oceans. They are the largest member of the dolphin family and are known for their intelligence, communication skills, and complex social structures.
Orcas are also known to be opportunistic hunters, meaning they will eat whatever prey is available to them. Their diet can include fish, seals, sea lions, and even other whales. However, this recent attack on sharks is particularly unusual.
A male and female orca pair named Port and Starboard, notorious for their previous eight great white shark killings, recently attacked 19 broadnose sevengill sharks (Notorynchus cepedianus), devouring their livers before leaving their carcasses to wash ashore on the southernmost coast of South Africa near Pearly Beach. This puzzling onslaught captured the attention of Alison Kock, a marine biologist at South African National Parks, who tweeted about the orcas' infamy and the frenzy that unfolded on February 23.
Orcas, Port and Starboard. Named for the direction in which their dorsal fins fall (Photo: Christine Wessels/MarineDynamics)
This marks the latest event in a series of shark attacks by the duo in the area. During their past sprees, the orcas consumed only the livers of their victims, an action that helped them become more proficient hunters. Sharks' livers are high in nutrients, such as fats and vitamins, which provide orcas with the energy they need. As such, they may have learned to consume these organs, which are easier to locate as they are large and buoyant, often floating to the water's surface upon the shark's death.
Orcas often hunt in pairs or groups, giving them an edge over their prey. One orca might distract the shark, allowing the other to attack. The intelligence and social cooperation required to carry out this technique is impressive. The orcas can also use their massive tails to flip sharks, rendering them motionless.
Such behavior has been observed in various locations worldwide, including South America, North America, Australia, and New Zealand. However, these attacks have only recently become more frequent among sevengill and great white sharks in South Africa. The death of so many sharks in a single day raises concerns about the consequences of this predation on the local ecosystem.
Kock believes that the orcas' expertise stems from experience, allowing them to remember where the liver is located in a shark and becoming more proficient over time. This expertise, coupled with the orcas' ability to work together, results in highly effective hunting techniques. The consequences of these hunts may be more far-reaching than the death toll of the sharks themselves. The absence of these top predators could lead to significant changes in the ecosystem.
Examining a shark carcass washed up on the beach.(Photo: Hennie Otto/Marine Dynamics)
There are several possible explanations for why these orcas carried out such a brutal attack on the sharks:
1. Food Shortage
One possibility is that the orcas were struggling to find enough food in their usual hunting grounds. Sharks are a relatively easy prey for orcas, and the livers are a particularly nutrient-rich part of the animal. It's possible that the orcas were simply taking advantage of a food source that they don't normally target.
2. Environmental Changes
Another possibility is that environmental changes have caused a disruption in the orcas' usual food sources. Overfishing, pollution, and climate change can all impact the availability of prey for marine animals. It's possible that the orcas were forced to adapt their hunting tactics in order to survive.
3. Social Learning
Orcas are known for their ability to learn from one another. It's possible that the orcas learned this hunting technique from another pod or group of orcas. This would explain why this behavior is so rare, as it may only be present in a small subset of the overall orca population.
4. Playful Behavior
Finally, it's possible that the orcas were simply playing. Orcas are known for their playful nature and are often seen engaging in what appears to be "play" behavior. It's possible that the orcas were simply having fun and not necessarily targeting the sharks for food.
The Impact on the Ecosystem
While this attack may seem shocking, it's important to remember that all species play a role in the ecosystem. Orcas are apex predators, meaning they are at the top of the food chain. By targeting sharks, the orcas may be helping to regulate the shark population and ensure that the overall ecosystem remains healthy.
However, it's also possible that this attack could have unintended consequences. Sharks play an important role in the ocean ecosystem, and their absence could have ripple effects throughout the food chain.