Discovery: Orca with Shark Bites Suggests Emerging Killer Whale Population in Northeastern Pacific

Researchers from UBC suggest that a pod of killer whales recently spotted hunting marine mammals, including sperm whales and even a sea turtle, in the open waters off California and Oregon, could signify a previously unidentified population.

In a recent study featured in Aquatic Mammals, the UBC team examines evidence indicating that the 49 orcas may represent either a distinct subgroup of transient killer whales or an entirely new oceanic population unique to the California-Oregon region.

Josh McInnes, a master’s student at UBC’s Institute for the Oceans and Fisheries (IOF) and the study’s lead author, remarks, “Observations of killer whales in the open ocean are exceptionally rare, given that it’s the largest habitat on our planet. This discovery provides valuable insights into the movements, ecology, and behavioral patterns of killer whales in high seas, distinct from those inhabiting coastal areas.”

The coastal waters of California and Oregon host three distinct ecotypes of killer whales: ‘residents’, ‘transients’, and ‘offshores’.

Although the presence of these unidentified orcas has been noted previously, a recent study presents a compelling body of evidence gathered from nine encounters spanning from 1997 to 2021, providing substantial grounds to propose the existence of a distinct population, according to the researchers.

Dr. Andrew Trites, a professor at IOF and co-author of the study, remarked, “Discovering a new population is quite exceptional. It requires significant time and effort to accumulate photographic and observational data substantial enough to distinguish these killer whales as unique.”

Despite thorough examination, the 49 killer whales observed could not be matched with any known individuals based on photographic or descriptive records. Josh McInnes, another co-author, recalled one of the initial encounters where researchers observed these oceanic killer whales engaging in a remarkable confrontation with a group of nine adult female sperm whales, ultimately claiming one. McInnes noted, “This incident marks the first documented instance of killer whales attacking sperm whales on the west coast.” Other notable encounters involved attacks on a pygmy sperm whale, predation on a northern elephant seal and Risso’s dolphin, and a period of apparent post-feeding inactivity following scavenging on a leatherback turtle.

Shark bite marks offer crucial insight.

A significant clue regarding the presumed habitat range of the newly discovered population is found in the cookiecutter shark bite scars observed on nearly all of the orcas. These scars, inflicted by a parasitic shark typically found in the open ocean, suggest that the new population primarily inhabits deep waters far from coastal regions.

In addition to these bite scars, the orcas exhibit distinct physical characteristics that set them apart from the three main ecotypes. Variances in dorsal fin shapes and saddle patch patterns—grey or white patches near the dorsal fin—are noted among the individuals. Josh McInnes explained, “While the sizes and shapes of the dorsal fins and saddle patches resemble those of transient and offshore ecotypes, there are noticeable differences. Some individuals display pointed fins akin to transients, while others have rounded fins similar to offshore killer whales. Similarly, saddle patch patterns range from large uniformly grey patches to smooth narrow patches, reminiscent of those observed in tropical killer whale populations.”

Dr. Trites highlighted the collaborative effort in gathering observations, including reports from marine mammal stock assessment surveys, fishermen, and passengers on open-ocean expeditions. Spotting these unidentified killer whales has become a popular pastime among fishermen, some of whom have invested in cameras specifically for such encounters.

The researchers aim to expand their documentation efforts, seeking more sightings and gathering additional data, including acoustic recordings of the orcas’ vocalizations and genetic analysis of DNA samples. These endeavors will provide further insights into the unique characteristics of this newly discovered population and its potential differences from established killer whale populations.