Jan 24

A distinct population of orcas in the north-east Pacific has been found to hunt sharks, a tough diet which wears down their teeth.

Photo of captive orca mouth detail

A captive orca showing its teeth. Also known as the killer whale, the orca is a widespread, intelligent and versatile predator.

As a species the orca has a very varied diet, but different orca populations are known to specialise in hunting different types of prey. For example, in the north-east Pacific, ‘resident’ orcas feed on fish, particularly salmon, while ‘transients’ specialise in marine mammals such as sea lions, other cetaceans and even large whales.

Photo of orca attempting to drown grey whale calf

Some orcas specialise in hunting marine mammals, including large species such as the grey whale.

Now a third type, the ‘offshore’ orca, has been shown to hunt sharks, providing the first evidence of the preferred prey of this population. The study, published in the journal Aquatic Biology, also found that the teeth of offshore orcas were typically worn right down to the gums – damage which was most likely caused by the tough, abrasive nature of shark skin.

Photo of orca beaching to attack sea lion

Orcas vary widely in their hunting techniques. Some orcas in Argentina have learnt to intentionally strand themselves to reach seals and sea lions on the shore.

Although further research is needed to determine whether these shark-eating orcas are as specialised as other orca groups, the findings of this study add weight to growing calls for different types of orca to be recognised as distinct species.

Photo of orca pod blowing air at the surface

Orcas are highly social, living in complex groups which often share a distinct vocal repertoire. Resident, transient and offshore orcas are not known to interbreed.

Not only do different types of orca specialise in different prey, but the distinct groups also vary in appearance and behaviour, and do not interact with each other. Recent studies have also highlighted genetic differences between them.

If the different types of orca are indeed found to represent separate species, it will have important implications for the conservation of these charismatic predators.

View a slideshow of 52 stunning orca photos on ARKive.

Liz Shaw, ARKive Species Text Author

  • hannah (June 16th, 2011 at 4:47 pm):

    i love orcas they allways been my fav seance i was little i still oove them noe i havent seen one up close but from the storys people tell me ther are the most amazing animal in the world i hope that i can get to see one.