Orcas

February 01, 2022

John Daw/Australian Wildlife Journeys

One of the articles on my weekend feed was a report published in Marine Mammal Science of three attacks by orcas on blue whales.  The scientific community has long debated if orcas can hunt the massive blue whales, and for the first time a pack of orcas have been observed hunting and killing the whales.  Three instances of packs of orcas attacking blue whales off the coast of Western Australia were recorded by marine scientists from Cetrec WA (Cetacean Research).  “Here we provide the first documentation of killer whales killing and eating blue whales: two individuals killed, 16 days apart in 2019, and a third in 2021,” researchers wrote in the paper. “Notably, the first whale taken appeared to be a healthy adult.”  The blue whale is the largest animal on the planet.

When I looked online, I found the blue whale (Balaenoptera musculusis) is the largest animal on the planet, growing up to 110 feet (33.8 meters) in length and weighing as much as 200 tons (approximately 33 elephants).  The blue whale has a heart the size of a Volkswagen Beetle and its stomach can hold one ton of krill.  These whales are the loudest animals on Earth (188 decibels) and are louder than a jet engine (140 decibels).  Their low frequency whistle can be heard for hundreds of miles and may be used to attract other blue whales.  The orca (Orcinus orca) or killer whale, is a toothed whale belonging to the oceanic dolphin family and is its largest member.  Orcas are recognizable by their black-and-white patterned body.  Orcas can be found in all the world’s oceans and in a variety of marine environments.  Blues and orcas are endangered and protected under the Marine Mammal Protection Act of 1972.

Orcas are highly social and can be found in very stable matrilineal family groups (pods).  Their hunting techniques and vocal behaviors are often specific to a particular pod and are passed across generations, all signs of animal culture.  When researchers arrived at the first 72-foot-long blue whale they saw large chunks of skin and blubber had been gouged from its body and most of the dorsal fin bitten off.  It was followed by relentless attacks by the orcas, where three lined up against the blue whale and pushed it underwater, while two attacked its head.  The study said 50 orcas joined the pack for six hours to feed on the carcass.  A few weeks later a 40-foot-long blue whale calf was targeted by twenty-five orcas.  The final recorded attack was on a 45-foot-long blue whale.  The orcas again pushed the whale under water while others attacked its head.  A pack of 50 orcas devoured the remains.  Previous studies thought orca attacks were executed by the bigger males.  This study documented the killings were led by female orcas.  The study suggested the drive to feed their offspring may make them more aggressive.

Thoughts:  Although the predation described of blue whales by orcas is gruesome, scientists say it could be a positive sign for the health of whale species in the area.  The whaling industry nearly drove blue whales to extinction, and having enough whales exist to be preyed on by orcas may hint at population growth.  Dr. Rebecca Wellard, who was among those who witnessed the 2019 attack said, “These hunts signal a positive step for both species’ populations.”  The interaction between predator and prey is part of the natural balance of life.  Humans throw this process out of balance when we refuse to regulate our actions.  Being at the top of the food chain does not give us the right to destroy the earth’s resources.  Follow the science.  Change is coming and it starts with you.

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