Orca
 

Common Name: Killer Whale or Orca

Class: Mammalia

Order: Cetacea

Suborder: Odontoceti

Family: Delphinidae

Genus: Orcinus

Species: Orcinus orca

Taxonomy/Description

Orcas belong to the Mammalian Order Cetacea, in the suborder Odontoceti.  All toothed whales belong to the suborder Odontoceti, which is Latin for "toothed whales".  The orca is the largest member of the oceanic dolphin family, Delphinidae.  Other members of this family include the bottlenose dolphin, long-beaked common dolphin, and pilot whale.  The orca's scientific name is Orcinus orca, which means "whale-like whale". 

Killer whales are black with white eye patches, white side patches, and a white underbelly.  A gray patch posterior to the dorsal fin is called the "saddle patch".  Males are larger than females, exceeding lengths of 30ft and weights of 8-9 tons.  Females usually attain lengths of about 20ft, and weights of four tons.  Adult males are also distinguished from females and juvenile males by their very large dorsal fins.  Females and young whales have curved dorsal fins, usually no taller than three feet.  Adult males however, have six foot tall, triangular dorsal fins.  These dorsal fins are the largest of all whales.

Habitat/Diet

The intelligence of orcas is widely known.  Marine parks throughout the world display killer whales as main attractions.  Orcas perform a wide variety of learned behaviors in marine shows.  Such playful interactions between orcas and humans has lead to the misconception that orcas are gentle animals of the ocean.  Killer whales are appropriately named.  They fiercely attack prey in cooperative hunting groups, feeding on a wide variety of prey.

Orcas are found in all oceans of the world.  Such a wide distribution  implies a varied diet.  Killer whales feed on a large variety of marine animals.  Thirty fish species, including salmon, herring, and shark species are hunted.   Even the largest shark, the whale shark, falls prey to the orca.  Five seal species, seven seabird species, sea lions, penguins, squid, sea otters, and sea turtles are common prey.  Larger aquatic mammals, like dugongs are also hunted.  Fascinatingly, 24 different species of cetacean are hunted by orcas.  Dall's porpoise isn't even fast enough to escape the orca.  The enormous size of baleen whales is not a deterrent either.  In fact, orcas seem to enjoy the baleen whale tongue.  After slowing down a much larger baleen whale by biting its fins and flukes, a killer whale pod will devour the tongue.  Eating to their fill, the orcas then leave the remainder of the carcass.  Successful attacks on sperm whales, the largest species of toothed whale have been documented.  Their wide distribution, variety of prey, group hunting technique, and aggressive hunting tactics have given rise to the nickname "wolves of the sea".

Behavior/Reproduction

Distinct populations of wild orcas exist.  This has lead to the development of characteristic vocal dialects and hunting techniques within populations.  While geographical location has a large part in the prey species an orca may hunt, some orca pods in the same region hunt different animals.  For example, two types of orcas live in the waters of the North American Pacific Northwest.  One type feeds primarily on fish species, mainly the Pacific salmon.  These killer whales are called "resident" orcas.  They do not travel far from this region, remaining there to feed on the continuous supply of local fish.  The second type of orca in this area feeds primarily on other marine mammals.  Harbor seals, gray whale, and harbor porpoise are just a few potential prey species.  These killer whales travel along the coast of North America, tapping a variety of different food sources.  The cause of differentiation between orca pods, and their relationships with one another are still unknown.  Incidentally, a third type of orca pod occasionally visits the Pacific Northwest.  Researchers refer to these pods as "offshore" orcas.  Little is known about where, what, or how they hunt, but it is assumed they have different techniques from the resident and transient orcas.

The social structure of such pods differs as well.  Resident orca pods are matrilineal and very stable.  Orcas in these pods remain with their mothers their entire lives.  Transient pods are more fluid, with mother and calf pairs entering and leaving pods.  The structure of offshore pods is currently being studied.  The year round presence of calves leads scientists to believe that orcas may breed all year.  After a gestation period of 16 months, a female orca gives birth to a single calf.  The calf is about six feet long, weighing 300-400lbs.  The calf will remain with its mother for 3-7 years.  A single female gives birth about every 8 years.  Females become sexually mature at 9-12 years of age.  Males reach sexual maturity at 13-16 years.  Male puberty is characterized by the growth of pectoral and dorsal fins.  Called "sprouting", the male's juvenile curved dorsal fin grows much larger and straighter.  His pectoral fins also become larger.  Females live longer than males, aging 80 years.  Males live well into their fifties.

Conservation

The global population of orcas is unknown.  It is estimated by some to be at least 100,000.  They have no natural predators.  Whalers did not hunt orcas as thoroughly as other whale species.  Orcas rely on fish directly, as their primary food source, or indirectly, eating marine mammals that feed primarily on fish.  Overfishing is therefore a threat to orcas.  Less available food resources will result in less orcas.  Water pollutants are dangerous to all cetaceans, the orca being no exception.  A decrease in water pollution and commercial fishing aid in killer whale conservation.

 

Content provided by Canisius College students under the direction of Michael Noonan, PhD.