Why This Cute Koala Has a Terrifying Roar

Koalas look cute and cuddly, but they sound terrifying. In this YouTube video, a young koala is booted out of its tree by an older male. While the youngster screams and throws a tantrum, the older male roars in the treetops like a lion. Who knew koalas could be so intimidating? Apparently, the sound designers of Jurassic Park did, because they used a male koala’s deep growls for the T Rex. But why are these koalas brawling, and what do their vocalizations really mean?

Koala Squabbles

Koalas (Phascolarctos cinereus) are arboreal marsupials that live high in the canopies of eastern and southeastern Australia. They have a specialized diet, eating almost exclusively the leaves of eucalyptus trees. This low-calorie diet requires them to maintain a low-energy lifestyle. Adult koalas typically spend around 20 hours a day sitting and sleeping. While koalas live in complex communities with some overlapping home ranges, they are generally solitary and rarely share trees, since trees are their primary food source.

During the breeding season, which is generally from August through February, the males can be highly territorial. Aggression is usually observed between males as they establish dominance. Fights most often occur when a koala attempts to access an already occupied tree. The typical response is submission, and serious attacks are rare. The non-dominant male typically leaves the tree but will remain at its base, as seen in the video. Young males become capable of breeding at around 18 months of age, but they typically do not begin mating until they are about 4 to 5 years old. This delay is primarily because older males prevent younger ones from mating until the younger males are strong enough to challenge them.

The Meaning Behind Koala Vocalizations

Koalas communicate through a variety of vocalizations. Male koalas bellow during breeding season to establish dominance and control their habitat. These uncannily low-frequency sounds, heard around the 33-second mark in the video, travel long distances to advertise the male’s location to females searching for mates. Announcing their presence also allows juvenile males to avoid conflict. Males emit screaming calls during fights or when they feel threatened by predators or competitors.

Females also bellow during the breeding season, but their bellows are shorter in duration and have higher frequencies than those of males. Female koalas scream, squawk, squeak, snarl, and wail when they reject a male’s advances or during conflicts. They emit soft, low grunts when disturbed or annoyed. Young koalas likewise squeak or wail when distressed, as heard in the video.

How Do Koalas Make Those Sounds?

Researchers have discovered that koalas have a special vocal organ that allows them to produce such incredibly low-pitched calls. The call consists of a series of inhalations and exhalations that average only 27.1 Hz. This frequency is on the lower end of the spectrum of human hearing, which is generally considered to be 20Hz to 20kHz. Scientists note that this is 20 times lower than expected for an animal of this size, and is more typical of animals as large as elephants.

Like humans, koalas have a descended larynx, which houses the vocal cords. This makes koalas’ vocal tracts longer and helps create more resonance. However, koalas also have larger folds in the soft palate, called velar folds, that vibrate to produce such low frequencies. The velar folds bridge the opening between the nasal and oral cavities of the pharynx, which is the part of the throat above the larynx and behind the nose and mouth. Scientists believe this is the first time a specialized organ for sound production, other than the larynx, has been found in a terrestrial mammal.

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