Sperm whales live in the depths of the ocean. They dive as deep as 900 meters (nearly 3,000 feet) to forage and spend only about 10 minutes of every hour on the surface. Their world is cold and dark, an environment other mammals would find extremely hostile.
“Sperm whales have evolved to adapt to a niche that is about as alien from our own as is possible to get without leaving the planet,” says Luke Rendell, biologist and co-founder of the Dominica Sperm Whale Project.
Here’s some of what we know about sperm whales and how they spend their lives in this alien world.
Sperm Whales Are Big
An adult male sperm whale can weigh up to 50 tons and reach 18 meters (about 60 feet in length — the distance from home plate to the pitcher’s mound in major league baseball).
One-third of that length is its head. That enormous head houses the largest brain of any animal that has ever lived on Earth. It also contains an organ that produces a substance called spermaceti. Whalers once thought this oily liquid was sperm, hence the name sperm whale. Scientists later thought the substance aids in adjusting buoyancy during diving and resurfacing. Now, it appears that spermaceti plays a role in the animals’ echolocation system.
Rendell describes the organ as “the world's most powerful biological sonar, a biological echolocation system for sending out very powerful and very directional clicks that are the fundamental sensory apparatus sperm whales use when foraging.”
Read More: 4 Ways Whales Show They are Highly Intelligent Creatures
They’re Voracious Eaters
Deep-water squid is the favorite food of sperm whales. And these whales devour a lot of squid. According to the Dominica Sperm Whale Project’s website, sperm whales “eat as much squid in a year as all of the biomass removed from the oceans by all of the modern human fisheries combined.”
Like many voracious eaters, sperm whales do not have delicate table manners. They grab a squid in their incredibly strong jaws, then suck the prey in whole, along with a lot of water.
They Practice Collective Child Care
One big challenge for sperm whales is what to do with the calves while the mothers are foraging. Young whales can’t dive that deep, so mom has to leave them higher up while she dives for dinner.
Sperm whales have evolved a cooperative system for dealing with that problem. Mother whales look after each other’s calves while other mothers are hunting. “Their social structure,” explains Rendell, “seems to be based around the principle of looking after calves.”
When it’s time for the calf to breathe, multiple animals escort it to the surface, Rendell explains, not just its mother. He adds that there is evidence that females also nurse each other’s calves. “The bonds formed in these female-based social units are very, very strong and long-lasting,” he says. “And those bonds are based on this kind of mutual care and raising of calves.”
A Spot of Good News
Sperm whale populations declined drastically for almost two centuries, starting around 1800. Then, in 1986, the International Whaling Commission declared a moratorium on commercial whaling. Since then the species has been making a comeback, if a slow one. (Today, sperm whales are listed as “vulnerable” on the IUCN’s red list, but the assessment hasn’t been updated since 2008.)
“I think the news is quite good for the medium term,” says Rendell. Population estimates are necessarily uncertain, he warns, but there are probably about one million individuals now, compared to an estimated three and a half million before the advent of commercial whaling.
“A massive reduction, but not down to a critical level,” he says. “I think they’re basically doing okay.”
Threats that remain include drift-net fishing (the whales get caught in the nets) and shipping. A subpopulation of sperm whales in the Mediterranean is considered endangered because so many are being hit by ships, Rendell says.
Read More: How Many Whales Are Left In the World?
Sperm Whale Mysteries Remain
There’s still a lot we don’t know about these animals. The big challenge is learning what’s happening below 100 meters (328 feet).
“What is it like for a sperm whale to be at maybe 100 meters and hear other group mates? How do they use that information? That's just a complete mystery,” Rendell says.
He adds that scientists have been studying these whales for only about 40 years, and they suspect that the whales’ lifespans may be in excess of 60 to 80 years, in some cases possibly over 100 years.
Close, yet Distant
There are many things that remind us that both whales and humans are mammals — their social lives, their mammalian eyes. But in other ways, they seem alien.
“What impresses me,” says Rendell, “is the simultaneous proximity and distance, the complete unfathomability of what it’s like for them.”
Do sperm whales have any lessons to teach us? Rendell does not hold with what he calls the naturalistic fallacy, the notion that if nature does it, it must be right. Even in whales and dolphins, he says, there are examples of behavior that humans would consider morally repugnant.
However, he does mention one thing: “Sperm whales prosper by working together, by collectively sharing risk and supporting each other in times of need. People can take from that what they want, but it has never ceased to impress me that that's how you survive a tough time, not by yourself.”
Read More: The Pygmy Right Whale Was the Family Weirdo, and it Never Went Extinct
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:
NOAA. Sperm Whale
Oceana. Sperm Whale
IUCN Redlist. Sperm Whale
Conservation Biology. Red-list status and extinction risk of the world's whales, dolphins, and porpoises
Avery Hurt is a freelance science journalist. In addition to writing for Discover, she writes regularly for a variety of outlets, both print and online, including National Geographic, Science News Explores, Medscape, and WebMD. She’s the author of Bullet With Your Name on It: What You Will Probably Die From and What You Can Do About It, Clerisy Press 2007, as well as several books for young readers. Avery got her start in journalism while attending university, writing for the school newspaper and editing the student non-fiction magazine. Though she writes about all areas of science, she is particularly interested in neuroscience, the science of consciousness, and AI–interests she developed while earning a degree in philosophy.
