The Dark Side of the Migration

It is common to wax nostalgic about the Gray Whale migration and frame it as a test of endurance for a very unique species on the road to recovery from the brink of extinction. The resolve and dedication of these animals to their task of which their entire agenda for the year revolves around. But what is not considered often is a part of the migration that some people may find distasteful. The role of the migration in the development and nourishment of the Bigg’s Killer Whale, also known as Transient Orca.

Unlike the Resident Orcas of the Salish Sea and the Pelagic (Offshore) Orca around the world who devote a lot of their time to the consumption of fish the Transient Orca subsist primarily on other marine mammals. They are the only cetacean to include mammals as a large portion of their diet. The only other marine mammal to share this trait are Polar Bears, who do feed on pinnipeds a lot and on cetaceans from time to time. Transient Orca are arguably the only predators of fully grown Baleen Whales, even large sharks only target calves in rare instances. Documented kills and attempted kills on Blue Whales, Fin Whales, Humpback Whales and more can be found with basic internet searches.

 The Gray Whale migration is an important part of the lifestyle of the Transient Orca of the North American West Coast. With the bulk of the world’s estimated 30,000 gray whales travelling between the Bering Sea to Baja and back it creates hunting opportunities for these voracious predators. A fully grown adult male Transient can consume 500 pounds of meat in just one day. Gray Whale calves provide an important source of food and as many as 30% of all Gray Whale calves born each season will fall prey to the Orca. 

 Experienced Gray Whale mothers will keep calves in shallow waters that Orcas do not care for and know the best ways to evade their enemies, but the feast and famine lifestyle does not always allow for a careful pace. If the baby is not born at the right time, fails to grow quickly, or if the female is losing calories too rapidly she will be more vulnerable to predation. The Transients also know the best spots for ambushes along the way, with one of the earliest gauntlets being Monterey Bay in Central California. One naturalist I have met theorizes that this is because the northbound Gray Whale calves by the time they reach the bay are much better targets. They lack the strength to defend themselves but possess more meat that southbound calves or calves just leaving Mexico. A Gray Whale calf grows 50 pounds per day and an extra month of development mean 1500 more pounds of calf to target. 

Hugging the coast is relatively low risk or the female Gray Whales but it does provide a safer, albeit slower route. However, upon entering Monterey Bay they find themselves having to go into the bay, where waters can still reach depths of over 2000 ft. Crossing the mouth of the bay leaves them even more vulnerable and is very risky. In April of 2016, Orcas have invaded the Bay without mercy and have made many kills of Sea Lions, Seals, Dolphins, and Gray Whale calves. The female is not defenseless and will fight to protect her baby until the cause is lost, but numbers almost always favor the Orca. In extremely rare instances Humpback Whales have been known to attempt to defend Gray Whales but this is not always successful or something gray whales can count on either. 

It pains some people to think about this fact of life, I myself want nothing but the best for the animals I care for but a good naturalist must accept that this is a part of life. I like to think of it as that the Orca babies need to eat also and that in nature an animal’s cuteness and human aesthetics are irrelevant in the circle of life. The Orca utilize the Gray Whale migration as a source of food for growing families and as a chance to show their young the hunting techniques they will need to support the pod later in life animals must consume other animals to survive, and predatory mammals need to kill even more to provide the nourishing milk that their young depend on in the early stages of life. Just because they consume another “likable” animal does not make that tragic. Maybe one doesn’t find the salmon consumed by Resident Orca as appealing or cute as the sea lions or young whales consumed by the Transient Orca, but the declining population of Chinook salmon compared to the large stabilizing population of California Sea Lions make the lifestyle choice of the Transient Orca to appear far more prudent. It makes more sense to be happy that the population of Gray Whales is strong enough to support the Transient Orca, in the same vein that a recovery of Salmon in the Salish Sea would benefit the Southern Resident Orcas. 

The role of the apex predator is to provide a counterbalance to otherwise unbeatable fauna. Occupying the top of the food chain comes with a great price, failure to thrive and injury is punished far more severely the higher a species ascends. Greater risks can be associated with greater rewards but only the most intelligent hunters are able to traverse such a fine line in the unforgiving ocean environment. The Transient Orca play the part of the unstoppable force in opposition to the baleen whales’ immovable object. Humans, especially those who consider themselves conservationists or naturalists, should not reject the aspects of nature that they find unappetizing by their own personal standards. Predation is a part of the natural world and is responsible for maintaining the balance of ecosystems. To understand the relationship between predator and prey is to learn fundamental truths about where these animals live. The knowledge gleaned can help preserve these animals and the waters they inhabit so that future generations of humankind can live alongside them as we do, hopefully in greater harmony that what exists now. 

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Categories: Gray Whales, Orca

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