Two Killer Whales Have Been Hunting Sharks For Half a Decade

Written by Alan Lemus
Published: August 7, 2022
Image Credit slowmotiongli/Shutterstock.com
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There are predators in nearly all the habitats on the planet. From rainforests, jungles, mountain summits, valleys, lakes, and oceans to arctic temperatures and hot desert climes, there’s a balance of nature between predators and their prey in practically every ecosystem that we know. 

In the struggle for survival, the prey and predator populations fluctuate. Although predators in a specific area regulate the numbers of prey species by ensuring that they do not become overpopulated and harm the habitat, other factors such as famine, weather, and disease outbreak also have an impact on populations.

Aside from the common assumption that predators are teeth-baring, jaw-growling animals, there exist predators of many sizes and forms. They might be as small as a bug or as large as an orca. Plants and microbes have predators as well; the Venus flytrap and the pitcher plant are carnivorous plants that eat insects. Other microorganisms are preyed upon by bacteria and protozoa

A Deep Dive into the Marine Ecosystem

15% of all species known to exist on Earth are aquatic. However, the sea is so big that it could be home to millions of species that are still undiscovered. By the unique design of nature, the marine world is home to some of the most incredible predators on the planet as well as a variety of fascinating and occasionally terrifying species. All of these amazing creatures are linked by a complex food web

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Simply put, a vast network of two major groups of interdependent creatures make up the marine ecosystem; the energy producers such as plants and phytoplankton, and consumers, including large and small plant- and meat-eaters. However, there are levels to the predation that exists in the benthic world.

The photoautotrophic level is at the base of the food chain in the marine ecosystem. Across the world, upper ocean waters are teeming with single-celled phytoplanktons in their numbers. By using photosynthesis to create organic molecules, these microscopic bacteria and plants utilize the sun’s energy to create nutrition and carbon dioxide.

They serve as the main providers of organic carbon, which is essential for the survival of all creatures in the ocean food web.

Following the ocean vegetation, are herbivores, which provide food for the top two carnivorous species on the food chain. Microscopic creatures known as Zooplankton, which include jellyfish and some fish larvae, barnacles, and mollusks, move around the ocean’s surface waters and feed on available food sources. Surgeonfish, parrotfish, green turtles, and manatees are examples of larger herbivores.

A wide variety of tiny predators, including sardines, herring, and menhaden, are fed by the zooplankton in the previous rung of the marine food chain. Larger animals like octopuses, which eat crabs and lobsters and numerous others that consume small invertebrates are also found at this level of the food chain.

Sharks, tuna, dolphins, pelicans, penguins, seals, and walruses are just a few of the varied species of huge predators that make up the top of the marine food chain. The majority of these apex predators are big, swift, and excellent hunters. Also, their reproduction rate is low and they have a lengthy lifespan.

The loss of a top predator can have a profound impact on the entire food chain. This is because the numbers of top predator species often take a long time to increase again after being reduced.

The Killer Whale Duo

In 2017, five great white shark carcasses—four of which had their livers removed—washed up on beaches in Gansbaai, Western Cape Province in South Africa, between the months of February and June.  Some were also missing their hearts. According to researchers, this wasn’t an isolated event as they’ve recorded at least 8 similar killings since 2015. 

Where did this all start? Well, let’s take you back to 1997. On October 4, 1997, tourists on a whale-watching vessel off the Southeast Farallon Islands, close to San Francisco, saw two killer whales attack a great white shark and eat its liver. At the time, it was the first recorded instance of killer whales eating a great white shark.

Great White Shark stalks diver
On October 4, 1997, two great white sharks were killed and eaten by killer whales. It was the first recorded instance of such activity.

Martin Prochazkacz/Shutterstock.com

According to researchers, the complete absence of great white sharks in the Southeast Farallon Island region after the attack was particularly interesting. Only two sightings of great white sharks were recorded between October 4th and December 1st which marked the end of the observation. This drastic shortage in sightings (which couldn’t be attributed to lack of prey or environmental conditions) and the chronological match with predatory attacks led to the assumption that the killer whales may have displaced white sharks. 

Back to the 2000s. False Bay in South Africa has always been an aggregation area for broadnose sevengill sharks and great white sharks. However, there were two predatory attacks on the broadnose sevengill sharks by killer whales in 2015 and 2016. Due to the way their dorsal fins floated, one to the left and one to the right, the killer whales were nicknamed Port and Starboard.

They used a unique feeding technique that involved only the liver of each shark. When CSI-style necropsies were conducted on the carcasses, the researchers found a neatly done tear between the two pectoral fins. The liver was sucked out of the open wound by the orcas, who apparently knew exactly where it was located. This predation on sevengill sharks in False Bay was the first confirmation of a new feeding strategy used by the killer whales.

Following the attack, Sevengill sharks stayed away from the largest known global aggregation site for their species for up to a month. Remember what happened in 1997?

Perhaps, it’s easy to see why orcas target the sharks’ livers. The liver of a white shark is extremely fatty and accounts for nearly a third of its total body weight. Unlike bony fishes, it gives predators a lot of energy and nutrients.

The migration of sharks from the local habitat could have an enormous impact on the ecosystem and food chain. Despite being fearsome, great white sharks play a crucial role in the balance of their larger habitat. The bronze whaler shark, a new mid-level predator, has arrived in the area to replace the role that great whites formerly played. Great whites often preyed on these sharks, but the researchers discovered that with the huge predators gone, bronze whaler sightings have greatly increased. Pressure on the entire ecosystem could result from this change, which could have an impact on the entire food chain.

What Does an Orca Look Like?

The largest members of the dolphin family are orcas. Males are often larger than females, though this varies based on the species of orca. According to SeaWorld, the largest orca ever measured was 32 feet (9.8 meters) long and weighed 22,000 lbs. (10,000 kilograms). That exceeds the length and weight of the majority of modern RVs.

Apex predator: Killer whales
Orcas are considered apex predators and they are the largest members of the dolphin family.

slowmotiongli/Shutterstock.com

Black and white color and a large dorsal fin are two characteristics that are distinctive to orcas. Their silhouette in the water is hidden by the black-and-white hue, which aids in their concealment. A gray area called a “saddle” is located directly beneath the dorsal fin and is so named because it resembles a riding saddle.

The cylindrical body of an orca tapers at each end to provide a hydrodynamic shape. With a top speed of more than 30 knots (about 34 mph or 56 km/h), the orca is one of the fastest marine mammals thanks to its unique shape, massive size, and strength. According to National Geographic, orcas have enormous teeth that can grow up to 4 inches (10 centimeters) long.

Up Next…

If you weren’t afraid of the ocean before you will be now. Take a look at a few of our other articles about just how crazy our oceans can be!

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About the Author

Alan is a freelance writer and an avid traveler. He specializes in travel content. When he visits home he enjoys spending time with his family Rottie, Opie.

FAQs (Frequently Asked Questions) 

What eats an orca?

No other predator can match the size and strength of killer whales, which are among the largest and most formidable creatures in the ocean. Thus, orcas are apex predators because they are at the top of the food chain.

Can you swim with orcas?

Yes, but because they are still wild animals, you must exercise extreme caution around them.

Do orcas attack humans?

In captivity, orcas behave quite differently, and assaults on humans by orcas have happened in zoos and aquariums. An orca that was housed at SeaWorld for 25 years, was responsible for the deaths of three humans at different times.

Are orcas dolphins or whales?

Orcas are actually dolphins in the dolphin family Delphinidae, despite being referred to as killer whales. Although they are the only species in their genus, Irrawaddy dolphins and other dolphins from Australia and South East Asia are their closest relatives.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.

Sources
  1. Science Trek, Available here: https://sciencetrek.org/sciencetrek/topics/predators/facts.cfm#
  2. National Geographic, Available here: https://education.nationalgeographic.org/resource/carnivores
  3. Nature, Available here: https://www.nature.com/scitable/knowledge/library/predation-herbivory-and-parasitim
  4. National Geographic, Available here: https://www.nationalgeographic.com/animals/article/killer-whales-orcas-eat-great-white-sharks
  5. National Geographic, Available here: https://education.nationalgeographic.org/resource/marine-food-chain
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  8. Syfy, Available here: https://www.syfy.com/syfy-wire/organ-eating-killer-whales-driving-sharks-from-territory#