Seals slap their bellies as a form of communication, primarily to show off their strength. It looks goofy, but it’s the seal equivalent of a gorilla beating its chest. Males use this behavior to warn rival males to back off and to signal their fitness to potential mates during breeding season.
A Show of Strength
The core purpose of belly slapping is dominance signaling. Seals clap their front flippers against their belly (or sometimes clap their flippers together) to produce a loud, sharp sound that broadcasts a simple message: I’m big, I’m strong, don’t mess with me. A 2020 study from Monash University captured the first underwater footage of a male seal clapping its flippers and found the sound was high-frequency enough to cut through ocean background noise, making it audible over considerable distance.
As lead researcher Dr. David Hocking put it, the claps carry two messages at once: “I am strong, stay away” and “I am strong, my genes are good.” The behavior serves double duty in competitive breeding grounds, both intimidating rivals and advertising quality to females.
How Males Use It in Conflict
Research on gray seal breeding colonies in the U.K. has documented what scientists formally call a “body slap,” a threat display used during male-on-male conflict. In one study, males performed body slaps in 66.3% of aggressive interactions, and more than half of all males at the colony used the behavior. Females never performed it. The slap was closely linked to other aggressive signals like approaching and open-mouth threats, and males who slapped more frequently were more likely to win their confrontations.
The slaps also produce vibrations that travel through the ground, and researchers found a direct correlation between a male’s body size and the strength of those vibrations. Bigger seals produce bigger slaps. This means the display honestly communicates a male’s size and fighting ability to any rival who can feel or hear it, even from a distance. It’s essentially a way to resolve disputes without the risk of actual combat, which can cause serious injuries between animals armed with powerful jaws.
Why the Belly Specifically
Seals don’t have hands or flat surfaces to clap against. Their thick layer of blubber, though, makes a perfect drum. When a seal swings its front flippers inward, the blubber on its torso provides a large, resonant surface that amplifies the sound of the impact. Some seals manage to clap their flippers together directly, but when their body gets in the way, the belly becomes the target instead. Either way, the result is a surprisingly loud crack that travels well through both air and water.
Harbor seals produce flipper slaps measured at 186 to 199 decibels underwater, roughly comparable to the sound of a small explosion at close range. Water transmits sound far more efficiently than air, so these slaps can reach other seals well beyond the immediate area.
What About Seals in Zoos and Viral Videos
Most people encounter belly-slapping seals through social media clips or zoo visits, where the behavior looks playful and comedic rather than aggressive. Scientists acknowledge there’s very little formal research on why captive seals do it. It’s possible the behavior retains some of its original confrontational meaning, directed at perceived rivals or even at humans nearby. It could also be a trained behavior reinforced by zookeepers, or simply a form of self-stimulation in an environment with less to do than the open ocean.
The honest answer is that researchers aren’t sure whether a captive seal slapping its belly on command is expressing the same thing as a wild male doing it on a breeding beach. Context matters enormously in animal communication, and the same physical gesture can carry different weight depending on whether there’s a rival, a mate, or a bucket of fish involved.
Not Just Seals
Flipper and body slapping shows up across marine mammals. Dolphins do it. Humpback whales roll onto their sides and slam their massive pectoral fins against the water surface in a behavior called pec-slapping, which serves similar communication functions over even greater distances. The pattern across species suggests that slapping a body part against water or against yourself is one of the few reliable ways to make a loud, attention-getting noise when you don’t have vocal cords designed for air and you lack hands to bang on things. Seals have landed on the same evolutionary solution as many of their marine relatives: use what you’ve got, and make it loud.