The Southern Resident Killer Whales are a unique subspecies of orca that inhabit the waters from central Vancouver Island to Puget Sound.
Their survival is closely tied to the fate of the Chinook salmon. Unfortunately, humans also enjoy eating Chinook salmon, and our hunting skills have advanced and become significantly more efficient than those of the orcas. Coupled with factors such as pollution and habitat degradation, the population of Southern Resident Killer Whales now stands at about 75 individuals.
Researchers are doing everything they can to protect this population. Under constant monitoring and protection, researchers unexpectedly discovered that since 1962, this southern resident whale species has exhibited puzzling behaviors. Occasionally, they harass and bully various species of dolphins, lifting the dolphin above water and balancing it like a ball! There have even been recorded instances where this behavior could potentially be lethal, yet they have never been observed eating these dolphins.
Although highly intelligent species like orcas sometimes display seemingly senseless behaviors, is it truly the case that this behavior has persisted for 60 years simply due to boredom?
Killer whales are highly intelligent (on par with primates) and are also the fastest marine mammals, capable of reaching speeds up to 56 km/h. Sometimes they appear to attack other animals in sight purely for “entertainment” rather than hunger. (Image: Livescience).
Orca experts Deborah Giles and Sarah Tyman noted in a study published on September 28 in the journal Marine Mammal Science that there were 78 recorded cases of Southern Resident Killer Whales harassing dolphins (from 1962 to 2020), with 28 instances resulting in death. The affected dolphins in 56 cases were harbor porpoises (Phocoena phocoena), 13 cases involved Dall’s porpoises (Phocoenoides dalli), and 9 cases were of unidentified dolphin species.
Deborah Giles stated, the Southern Resident Killer Whales have a completely different ecosystem and culture compared to mammal-eating orcas. They primarily eat fish. Therefore, these one-sided interactions between them and dolphins must serve a purpose, although the specific reasons remain unclear; researchers can only speculate about the motivations behind this behavior.
Interestingly, when killer whales are hunting, the surrounding area is filled with their sounds. It seems they are discussing tactics and plans for attacking prey, but through various studies, zoologists have analyzed these sounds and found that they mean the exact opposite of initial assumptions. Their noise is essentially a series of taunts, insults to each other, and reprimands directed at their prey. (Image: Livescience).
- Social interaction or simply playing: When Southern Resident Killer Whales harass dolphins, they do so in groups, suggesting this could be a social game among the orcas. Highly intelligent species like them may engage in and organize fun activities to establish connections and communicate with their peers.
- Practicing hunting skills: Another hypothesis is that Southern Resident Killer Whales harass dolphins to hone their salmon hunting skills. Dolphins are considered suitable moving targets for practicing hunting skills, even if there is no intention to consume them.
- Maternal instinct: About 70% of female Southern Resident Killer Whales experience miscarriages or die shortly after giving birth due to malnutrition. This leaves them with fewer opportunities to care for their young, and their maternal instincts may be misdirected towards dolphins, which are also marine mammals. They are small and cute, resembling baby orcas.
Killer whales also have different “ethnic groups,” which means they possess various dialects. When two pods of killer whales meet, they often produce sounds to greet each other, sharing hunting experiences and sometimes teaching each other insults. (Image: Livescience).
Despite these intriguing speculations, Deborah Giles and Sarah Tyman acknowledge that the exact reason behind the harassment of dolphins may never be fully understood, but one thing is certain: they do not eat dolphins.
Killer whales are incredibly complex and intelligent animals, and this dolphin harassment behavior is unethical but also a bond passed down from generation to generation, lasting over half a century.
Killer whales exhibit highly social behavior; they are matriarchal animals, with the basic social unit of killer whales typically consisting of 5-6 members from the same family, or closely related individuals forming communities. Communities with a common ancestor become clans. The relationships among family members of killer whales are incredibly tight-knit, comparable to human societies. While they live in a matriarchal structure, mature male killer whales may remain in their pods, temporarily joining another pod to mate before returning to their own. In contrast, mature female killer whales can separate and form their own pods. (Image: Livescience).
