Then, when your Aunt Mary helpfully points out that whales don't have hands, you can tell them that for decades, scientists thought only humans had a population-level preference for one hand (90% of us are righties; lefties are more commonly
men); however, more recently, scientists have noticed that some animals do, too.
If this sends your family into a debate about evolution, you may prefer to keep this trivia to yourself; if, however, your family geeks out over science, here's what you need to know to sound smart. (Save the detail about cats' preferred handedness until the end. You probably don't want your family to run off to check whether Mr. Anderson Pooper is a southpaw or if Woof Blitzer is a rightie before dessert.)
published in Monday's edition of Current Biology, takes a closer look at blue whales
, the largest animals on the planet. Researchers used high-tech sensors to track every detail of an animal's movement and found that whales roll their bodies to eat.
When blue whales come across a large patch of krill, the tiny crustaceans that make up their main meal, they do side rolls, but when they go after the smaller krill patches closer to the surface, they do full barrel rolls
, shooting straight up in the water.
With side rolls, the majority go right, suggesting that they're righties. But when the whales go up for surface krill and there is light, they do barrel rolls to the left. Scientists think they switch up their behavior when they go to the surface so they can keep their dominant eye on their prey.
"When facing upwards and dealing with counter-shade, we think they want to see these smaller prey patches," said study co-author Ari Friedlaender
, an association professor at Oregon State University. Unlike humans who can compensate for challenges in nature -- for instance, a left-handed bass guitar for lefties like the Beatles' Paul McCartney -- whales need to maximize what they have.
"Animals are not evolved enough to do things that are not efficient," Friedlaendar said. "These animals are so massive and have such big energetic demands, they need to be as efficient as possible when they feed."
Friedlaender said the idea for this study came after a right-side preference was observed in humpback whales
. Like humans, about 90% of humpbacks tend to roll right. Earlier studies
have found more scarring on the right jaw than the left from chasing fish that hide in the sand. Similar studies in
belugas show a right preference.
Scientists used to think
that hand dominance was reserved for humans and was a hallmark of our evolution, but it appears many vertebrates and even some non-vertebrates have a side preference, as well.
Studies have shown
that chimp and bonobo populations tend to show a right-handed preference, as do gorillas. Orangutans as a population do not seem to have a preference, although the individual animal uses a preferred hand.
Some kangaroo species tend to be lefties, studies show.
In one study, horses showed a left eye
preference, so they would be considered right-handed because the dominant eye corresponds with the opposite hand dominance.
Scientists bred several generations of mice that they noticed were more often using their left paws to get treats. The lefties' offspring was evenly split between righties and lefties. In that case, scientists concluded that the paw a mouse uses is purely chance
And when it comes to cats, a 1991 study
found that 40% were left-pawed, 50% were right-pawed, and 10% were, well, cats. Those animals were seemingly indifferent to one paw over the other. Another cat study
found that females tend to be more right-pawed and male cats tended to be more left-pawed.
in dogs showed a divide
. Scientists say you can try this experiment at home by seeing which paw they more typically use to reach for a treat, just mind the claws.
Handedness in an octopus sounds like a trick question, since they have eight arms, but scientists experimented anyway
and found a 50-50 split between righties and lefties. Although all eight of their arms are capable of doing the same things, the animal tends to favor one arm over another when hunting or grabbing or when they are holding "hands" and romancing their mates. Scientists think
that favorite tentacle typically corresponds with their dominant eye.
Scientists aren't entirely sure why there seems to be a tendency for a particular kind of handedness within a species, nor do they really know why some of us are lefties or vice versa. Some think it is about efficiency. Some think it helps in social species; when birds fly together, it's easier if they prefer to fly in the same direction.
So why should we care whether whales -- or any other animals -- prefer to use one side? Friedlaender said the more we know about typical behavior for an animal, the more we can understand what impact a disturbance will have on it. Blue whales were nearly hunted to extinction in the 20th century, but they've slowly been recovering through conservation efforts and restrictive laws.
seven-year project in partnership with the US Navy to understand whether naval sonar had an impact on whales determined it had an impact when they were feeding deep. After a federal court settlement, the Navy agreed to limit its use of sonar. When the sonar problem is combined with warming ocean trends that are affecting the amount of krill available, research suggests, the animal could be hurt.
"The cumulative effects can add up," Friedlaender said. "It's not dire everywhere now, but the point is, we are trying to understand and quantify animal behavior to help while we can."