In January 2009, a research team sailed from South America toward Antarctica. They hoped to document how killer whales, also known as orcas, worked together to create a wave that could knock a seal from the safety of an ice floe.
The team observed a pod of 10 orcas around two humpback whales. The whales were agitated, and the team initially thought the orcas were testing to see if either whale was weak. But when they reviewed the video footage, they saw a seal tucked between the massive whales.
Defeated, the predators moved on. Fifteen minutes later, the pod targeted another seal by creating a wave that broke the floe and left the doomed seal stranded on a small piece of ice. Before the killer whales could attack, the same humpback whales came to the seal’s rescue.
But why would a humpback whale spend energy protecting a seal? Scientists have been studying this unique behavior and believe they have a better understanding of why humpbacks play hero.
Why do Whales Save Seals?
Marine ecologist Robert L. Pitman was on the research vessel that saw the two humpback whales protecting the seals from orcas. In the years since, similar videos have surfaced of humpbacks protecting potential prey.
“It is pretty dramatic behavior, especially once you know what is going on, and people often post about it online somewhere,” says Pitman, a marine ecologist with the Marine Mammal Institute at Oregon State University.
The humpback whale (Megaptera novaeangliae) is a massive animal, weighing as much as 40 tons and stretching as long as 60 feet. Killer whales (Orcinus orca) are considered the ocean’s top predator, but they are much smaller. At max, they can weigh 11 tons and grow to 32 feet.
A healthy humpback adult can fend off an orca. But a calf, an injured, or elderly adult can fall prey. Scientists think this vulnerability may be motivating for humpbacks.
Read More: Humpback Whales Offer Humans Giant Bubble Smoke Rings as a Token of Friendship
Humpback Whales Protecting Others
In a 2017 article in Marine Mammal Science, a team of researchers collected more than 100 accounts of interactions between humpback whales and orcas. The observations came from people around the world, including researchers, naturalists, and passengers on whale-watching tours.
The team distinguished between the two types of orcas — fish eaters and mammal-eaters. The mammal-eaters pose a threat to humpback whale calves, and the study found that humpback whales were more likely to go on the offensive with these types of orcas.
The observers didn’t always see who instigated the encounter. But when the initiator was known, the study found that humpback whales approached orcas 58 percent of the time. Most of these were mammal-eaters who were in the midst of attacking prey or had already started feeding. The observers reported seeing the humpbacks interrupting attacks on their own kind 17 percent of the time. In the other 83 percent of encounters, the humpbacks went on the offensive for other species such as other whales, California sea lions, and harbor seals.
In comparison, orcas approached the humpback whales 42 percent of the time. In most of these instances, the orcas were mammal-eaters who targeted a calf or young humpback. In two reports, the observers thought the orcas were successful in their kill.
Humpback Heroes?
Although Internet commenters might think humpback whales are being altruistic when they come to the rescue, scientists think this behavior must somehow benefit the whales because the attack could be another humpback whale, and it could be a relative.
Mammal-eating orcas move silently when hunting prey, but they become quite vocal when the attack begins. These sounds can alert humpback whales who are miles away.
One question that remains is why humpback whales continue to defend prey once they arrive on the scene and realize the orcas aren’t targeting another humpback.
Pitman thinks it’s not so much that the humpbacks are driven to save the seals. Rather, they have an instinct to fend off orcas, and other species benefit.
“We called it ‘inadvertent altruism,’” Pitman says.
Read More: Rare Humpback Whale Calf Sighting Makes Migration Routes More Mysterious Than Once Thought
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- Natural History. Save The Seal
- NOAA. Humpback Whale
- NOAA. Killer Whale
- Marine Mammal Science. Humpback whales interfering when mammal-eating killer whales attack other species: Mobbing behavior and interspecific altruism?
