Innovative hunting strategies have been developed by a group of orcas occupying the open sea off California’s coast, as they have honed their skills in capturing oceanic prey.
These killer whales, with a diet predominately composed of other marine mammals, need to ensure their hunting expeditions are efficient to sufficiently nourish their pods.
While coastal environments offer easier prey capture due to natural traps provided by the landscape, these conditions can lead to intense rivalry. Venturing into the vast sea may present a bounty of food to those who can master the art of catching elusive marine fauna.
The transient orcas of the Northeast Pacific have discovered that preying upon seals and juvenile whales can be achieved by employing a blend of strategy and physical force. Using their bodies to ram or tail-slap their prey incapacitates it, paving the way for the orcas to feast.
“The subset of transient killer whales studied around Monterey Bay demonstrated a preference for the openness of the ocean, deep waters, and targeted seasonally present prey like California sea lions, calf gray whales, and northern elephant seals,” articulates a research team headed by Joshua McInnes, a marine biologist from the University of British Columbia.
“These particular whales employ distinct hunting techniques compared to methods observed in shallower, coastal waters that feature reefs and islands.”
Orcas worldwide form subgroups that are genetically and culturally unique from each other, known as ecotypes. Three of such ecotypes can be identified in the Northeast Pacific Ocean – the resident, transient, and offshore groups.
These distinct ecotypes follow their own distinct lifestyles; despite occupying adjacent regions of the ocean, they present unique genetic markers, possess distinguishable physical traits, have diet preferences that vary, and avoid intermingling or breeding together. They also communicate in distinct dialects.
Orcas that are transient by nature specialize in hunting other marine mammals, including seals, dolphins, and other types of whales. As the majority of human populations are land-based, our observations of their coastal hunting patterns are relatively thorough and well recorded.
Since the late 1980s, research has recognized that some transient orcas roaming Canada’s offshore seas employ alternative techniques, as classic coastal strategies are not viable further out to sea. Determining how these orcas succeed in their offshore hunts became a subject of scientific interest.
Investigations involved analyzing swathes of data, such as marine mammal surveys from 2006 to 2018, and whale watching records from 2014 to 2021, which were amalgamated into a comprehensive orca encounter database.
From 2006 to 2021, behaviors and pod dynamics of the outer coastal transient orcas were recorded in correlation with the seasons. The most frequent encounters happened in the spring when gray whales journey north after calving on the coast of Mexico.
The open water encounters depicted orcas hunting sea lions, northern elephant seals, dolphins, porpoises, and gray whale calves.
For hunting sea lions, the orcas would encircle and take turns charging at their prey, utilizing their heads or tails to make an impact or launching the sea lion skyward. The sea lion’s downfall would be shared among the pod, or carried as a prize for a duration. The hunting of elephant seals displayed slight variation, with orcas encircling the seal, tail-striking it, and then violently shaking it by its fins.
Adult female orcas typically would lead the chase during gray whale calf hunts. Forcing separation between the calf and mother through exhaustion, the orcas would then drag the calf away, proceeding to ram and bite it, and even smothering it by jumping on its blowhole.
Dolphin hunts displayed an exceptional level of coordination, with orcas cutting through large pods to isolate individuals. Once isolated, orcas would propel dolphins into the air by ramming them from below or dragging them underwater until lifeless. Porpoises fell victim to similar methods.
According to the researchers, understanding these behaviors offers insight into the complexity of the North Pacific ecosystem dynamics and the role of orcas as apex predators within it. It also aids in deciphering population trends and behaviors of prey species within these waters.
“Transient killer whales are predominantly documented within shallow coastal waters; the mysteries of their behaviors in offshore and pelagic deep-sea environments remain relatively unexplored,” the researchers comment.
“Our study illuminates the intricate predation behaviors and ecological significance of transient orcas as they dominate vibrant deep submarine canyon systems and their intertwined relationships with various marine mammal prey populations in the North Pacific Ocean.”
This study has been documented in the journal PLOS ONE.
FAQ
- What are the main prey species of the transient orcas in open waters?
- The transient orcas primarily hunt California sea lions, gray whale calves, and northern elephant seals.
- How do transient orcas differ from other ecotypes in the Northeast Pacific?
- Transient orcas differ in their genetic makeup, physical characteristics, prey preferences, and they have distinct vocal communication, separating them from resident and offshore ecotypes.
- What techniques do orcas use to hunt different marine mammals?
- Orcas employ strategies such as surrounding, ramming, tail-striking, launching prey into the air, dragging, and smothering to catch sea lions, elephant seals, gray whale calves, dolphins, and porpoises.
- Why is studying transient orca hunting behaviors important?
- Learning about their hunting behaviors helps scientists understand the roles of orcas in the marine ecosystem, how they impact prey populations, and provides context for environmental and ecological models.
Conclusion
The innovative hunting tactics of transient orcas in the open sea signify the adaptability and intelligence of these apex predators. As researchers continue to uncover the depth of orca behavior in offshore environments, it contributes substantially to our comprehension of marine ecosystems and the delicate balance maintained within them. This research not only enriches our knowledge but also emphasizes the importance of conservation efforts to preserve the natural behaviors and habitats of such crucial marine species.
