The Story of 0319: Part 2, Orca Ecotypes and Identifying Our Orca

In the previous blog post, I wrote about our initial observation and field necropsy of Orca 0319 back in November of 2011. Now, I’ll go over the different types of Orcas, called “ecotypes.”

There are currently 10 forms (“ecotypes”) of Orca recognized. They are all considered to be the same species (Orcinus orca) until proved otherwise by genetic research. In the Eastern North Pacific Ocean, three of these ecotypes occur: resident, transient, and offshore. The three ecotypes look slightly different (distinguishable by their saddle patch and dorsal fin), have different vocalizations, behave differently, and eat different foods.  

Check out this poster from Southwest Fisheries Science Center for a great illustration of the different ecotypes.

Resident

The best‐known form that lives off the coast of Washington and Oregon. The Southern Resident population is protected under the Endangered Species Act. Their saddle patch often has a large black intrusion (‘open’ saddle) not found in other Orcas. Females’ dorsal fins are rounded on top with a pointed trailing edge. They specialize in eating fish, typically salmon.

Transient

A large form that lives in coastal and offshore waters of the North Pacific. Their saddle patch is 'closed’ compared to the Resident forms’ and extends forward past the midline of the dorsal fin. Females’ dorsal fins are generally pointed. They eat mammals such as harbor seals and minke whales.

Offshore

A smaller form that is rarely observed because it occurs mainly over the outer continental shelf of the eastern North Pacific. Some travel between Alaska and Southern California. Their saddle patch is fainter than those of resident and transient forms. Females’ dorsal fins are rounded at the tip and often have nicks. In 2011, using genetic samples from prey remains, researchers determined that their primary diet consists of sharks (Pacific sleeper sharks in that case). The fact that sharks have rough skin explains why offshore Orca teeth are often worn to the gumline.

On Tuesday November 29th, we emailed photos of our Orca to various Orca researchers for possible photo identification. Later that day, Graeme Ellis, research technician at the Department of Fisheries and Oceans Canada, identified the Orca as O319, an offshore animal. O319 was originally sighted in 2002 as a juvenile and had most recently been recorded off the west coast of Vancouver Island in September 2011. Based on the photos, size, and lack of secondary sexual characteristics (curled flukes, large dorsal fin) Graeme Ellis estimated that O319 was approximately 15 years old at the time of death – still not a full adult.

Offshore orcas are a rare ecotype to find washed up on the beach, as they typically sink into the ocean after they die. This fact made Moe decide to collect the entire skeleton so that we could have as much research material as possible available for this animal.

Stay tuned to find out how we collected and cleaned the orca skeleton, leading up to the beginning of our articulation project. We’ve already begun articulating, so be sure to come by the Orca lab in the Piazza (Tuesday through Sunday) to see us in action!

Laura Wilkinson
Curatorial Assistant and Specimen Preparator
Ornithology and Mammalogy

All marine mammal stranding activities were conducted under authorization by the National Marine Fisheries Service through a Stranding Agreement issued to the California Academy of Sciences and MMPA/ESA Permit No. 932-1905/MA-009526.