Orcas are killing Great White Sharks in Mossel Bay, South Africa
Orcas, also known as killer whales, are renowned pack hunters. In fact, they are often called the “wolves of the sea,” due to their ability to hunt as a collective (1). Spanning a maximum of thirty-three feet long and weighing up to six tons, orcas are the largest members of the dolphin family (2). Although orcas are not whales, they are often dubbed, “killer whales,” due to their tendency to hunt large whale species (2). A pod of orcas is even capable of killing a blue whale, the largest animal on earth (3). Orcas have been spotted hunting large whales for centuries, but recently a new phenomenon has arisen: orcas are killing great white sharks (4).
In May of 2022, drone footage showed five orcas tracking down and killing a great white shark in Mossel Bay, South Africa (5). Before this encounter, limited footage of such an event existed (5). In fact, according to Alison Towner, a Ph.D. candidate at Rhodes University, “this behavior has never been witnessed in detail before, and certainly never from the air” (5). Ten days before the attack, cage divers saw an average of three great whites a day. Forty-five days after the attack, zero great white sharks were observed in the same area (5).
The number of orca-related great white shark deaths first spiked in Mossel Bay in 2017. Port and Starboard, two orcas who were first seen in the Mossel Bay region in the mid-2010s, are notorious great white shark killers (6). Since 2017, approximately eight great white sharks have been found dead with Port and Starboard’s teeth markings (6).
To determine whether the dwindling great white shark population in Mossel Bay is due to increased orca attacks, researchers at South Africa’s Dyer Island Conservation Trust conducted a five-and-a-half-year study in which they tagged the sharks and then tracked their movement in and out of the Bay (7). During that period, fourteen great white sharks were observed leaving regions in which an attack on sharks by orcas had occurred. During this same period, the average number of great white shark sightings decreased significantly. Together, this data suggests that attacks on great white sharks by orcas have not only influenced the population of great white sharks overall, but also, where great whites have chosen to live (7). Towner is convinced that these disappearances are indicative of a larger shark decline to come. She reports, “Initially, following an orca attack in Gansbaai, individual great white sharks did not appear for weeks or months…the more the orcas frequent these sites, the longer the great white sharks stay away (7).”
Towner is concerned that if orca attacks increase, great white sharks will continue to flee the Bay (6). A decreased number of great white sharks could have a severe impact on both the Mossel Bay ecosystem and the shark tourism industry (6). Orcas are powerful creatures capable of destroying great white sharks and the structure of entire ecosystems. Thus, given these recent developments, one has to ask, are orcas now the ultimate apex predator?
Port and Starboard: The Mossel Bay Great White Shark killers.
Bibliography:
- Martino, N. (2017, March 30). Wolves of the Sea: Killer Whales and the First Observed Predation on Beaked Whales in the Southern Hemisphere. PLOS blogs. Retrieved from https://everyone.plos.org/2017/03/30/wolves-of-the-sea/.
- Facts About Orcas (Killer Whales). Whale and Dolphin Conservation. Retrieved from https://us.whales.org/whales-dolphins/facts-about-orcas/.
- Wetzel, C. (2022, February 4). Scientists Witness Orcas Kill Blue Whale for the First Time. The Smithsonian Magazine. Retrieved from https://www.smithsonianmag.com/smart-news/scientists-witness-orcas-kill-blue-whales-for-the-first-time-180979522/.
- Pannett, R. (2022, October 6). Orca vs. shark: Rare drone footage shows killer whales mauling great whites. Washington Post. Retrieved from https://www.washingtonpost.com/climate-environment/2022/10/06/orcas-hunt-kill-great-white-shark/.
- Sguazzin, A. (2022, October 6). Rare Footage of Orcas Hunting White Shark Sheds Light on Disappearance. Bloomberg Magazine. Retrieved from https://www.bloomberg.com/news/articles/2022-10-06/a-drone-captured-footage-of-orcas-eating-a-white-shark-the-sharks-fled-the-area?leadSource=uverify%20wall.
- Goodyear, S. (2022, October 7). Footage shows pod of orcas killing a great white shark and devouring its liver. CBC Radio. Retrieved from https://www.cbc.ca/radio/asithappens/footage-shows-pod-of-orcas-killing-a-great-white-shark-and-devouring-its-liver-1.6610075.
- Coxworth, B. (2022, July 5). Study suggests orca attacks are scaring away great white sharks. New Atlas. Retrieved from https://newatlas.com/biology/orca-attacks-great-white-sharks/.