Hippos are semi-aquatic mammals known for their imposing size and complex social behaviors. They communicate through a variety of vocalizations and physical displays, revealing a sophisticated “language” that helps them navigate their watery habitats and social structures.
The Sounds of the Hippo
Hippos produce a diverse array of vocalizations, each serving distinct purposes. One of their most recognizable sounds is the “wheeze-honk,” a loud call that can carry for over a mile, reaching volumes up to 115 decibels, comparable to a loud rock concert. These calls are often described as a mix of a wheeze followed by a honking sound.
Beyond the iconic wheeze-honk, hippos also emit deep, rumbling grunts that can signal their presence or assert authority. They generate loud roars and growls, particularly during aggressive interactions or when asserting dominance. Other sounds include squeals, honks, and snorts, which are frequently used during social interactions.
Hippos communicate both above and below the water’s surface. About 80% of their vocal communication occurs underwater, producing specific sounds. These include tonal whines, linked to submissive behavior, pulsed croaks heard during interactions between calves and sub-adults, and click-like sounds for communication.
What These Sounds Mean
Hippo vocalizations convey social and territorial messages. The “wheeze-honk” serves as an identity signal, allowing hippos to recognize individuals from their own group versus strangers. Studies show hippos respond more intensely and aggressively to unfamiliar calls, often with increased vocal responses and territorial displays.
Grunts are used as warning signals to potential intruders, helping hippos assert their presence and claim territory. Roars and growls are associated with conflict, such as fighting between males or expressing anger. A rapid series of honks can indicate aggression, while softer honks might suggest a more relaxed or playful mood within the group.
Hippos also use infrasound, low-frequency vocalizations below human hearing. These deep rumbling sounds can travel distances through both air and water, allowing hippos to communicate across vast areas, even when submerged. Transmission through their fatty necks and jawbones aids effective underwater communication.
Other Ways Hippos Communicate
Beyond vocalizations, hippos employ various non-vocal methods to communicate. One notable display is the “yawn,” a visual threat display, not a sign of tiredness. When a hippo “yawns,” it opens its mouth wide to expose its large teeth and tusks, signaling dominance or aggression, especially when threatened or defending territory.
Scent marking is another communication tool. Hippos engage in a behavior known as “dung spraying” or “tail-waving dung spreading.” They rapidly flick their tails to scatter their feces, marking their territory and sending a clear message to other hippos.
Body language plays a role in hippo interactions. An open-mouthed display, distinct from a yawn, can serve as a direct threat. Dominant hippos may flap their ears or raise their heads high out of the water, while submissive behaviors include lowering heads, flattening ears, or rolling onto their backs to avoid conflict.