Page 28 - ARUBA TODAY

A28 SCIENCE
Friday 19 May 2017

Orcas prey on great white sharks in South African waters

CHRISTOPHER TORCHIA — considerably larger than of the Florida Program for predators and while we prey and different hunt-
Associated Press great white sharks. Shark Research . But small- are accustomed to view- ing strategies,” said Boris
JOHANNESBURG (AP) — “It’s just a classic sort of er sharks can be a rou- ing great white sharks as Worm, a marine research
The great white shark is scenario of what orcas are tine part of an orca diet, occupying the top of the ecologist at Dalhousie Uni-
one of the ocean’s most capable of doing,” said and studies have shown food chain in our waters, versity in Nova Scotia, Can-
powerful predators, yet it Alison Towner, a marine that the rough texture of orcas are much more spe- ada.
is sometimes prey for or- biologist with the Dyer Is- shark flesh grinds down the cialized hunters and con- “Offshore orcas are rare,
cas that killed several of land Conservation Trust , enamel on orca teeth over sider almost anything in the and very mobile, so it is
the formidable creatures which seeks to protect the time, he said. ocean as potential prey,” very conceivable that they
off South Africa’s coast this show up in an area where
month. they were previously not
Rare autopsies conducted seen and exploit sharks in
on carcasses that washed that region,” Worm wrote
ashore show how orcas in an email to The Associ-
dominate the marine food ated Press. “Of course, a
chain at the expense of white shark would be a
great white sharks, whose difficult prey to tackle due
ferocious reputation to its power and size, but
(thanks partly to the 1975 orcas (again like humans)
movie “Jaws”) belies their use group hunting strate-
vulnerability to shark nets, gies that can outsmart al-
fishing, poaching, pollution most any prey.”
— and the biggest mem- Orcas have been seen
ber of the dolphin family. attacking cow sharks off
Orcas, which also face hu- Cape Town, New Zealand
man threats, have a softer and South America. Addi-
image (the 1993 film “Free tionally, orcas were filmed
Willy” helped) due to their attacking great white
intelligence and accessi- sharks around the Farallon
bility at water parks. islands off California and
Bite marks on the carcass- Neptune islands off Austra-
es in South Africa were lia.
inflicted by orcas seen re- In this photo taken Wednesday May 3, 2017 and supplied by Marine Dynamics, a great white South African cage-diving
cently near Cape Town, shark is autopsied on a beach in Gansbaai, South Africa. operators reported a drop
conservationists said. The Associated Press in great white shark sight-
livers of all three sharks ings around the time that
were removed, suggesting fragile ecosystem in waters Two of the sharks in South the department said. It said the three sharks were killed,
the orcas, also known as around the southern tip Africa were recovered in the mammals have highly a sign that other sharks had
killer whales, targeted the of Africa. Towner partici- Gansbaai and another in developed social groups left the area, at least tem-
nutrient-rich oil and fat in pated in autopsies on the Struisbaai. Closer to Cape as well as a large brain, the porarily, because of the
the organs and discarded sharks, providing rare con- Town, several cow shark capacity to learn and the orcas.
the rest of their prey. firmation of orca killings of carcasses were discovered ability to locate with the Researchers are debating
Each of the sharks had a the big fish off South Africa. with their livers removed in help of sound waves that the size of South Africa’s
big wound on its under- Even if they have an ad- False Bay after orca sight- bounce off objects. great white shark popula-
side, a sign of the dexterity vantage, orcas are unlikely ings, South Africa’s depart- “Orcas are known to have tion and say more inquiry is
of the orca, whose biggest to hunt great white sharks ment of environmental af- culture, much like humans needed. Human threats far
males can be well over on a regular basis, said fairs said . do, and different orca cul- outweigh any threat from
nine meters (30 feet) long George Burgess, director “Killer whales are apex tures specialize on different orcas, they say.q