Do is educational: small, lazy koalas sound like they're snoring, belching and growling at the same time. All this is because of the extra pair of vocal folds above the throat. With this roar, the males claim territory, and during the mating season they attract females. The stronger this belch, the greater the chance of leaving offspring.

Do is educational: small, lazy koalas sound like they're snoring, belching and growling at the same time. All this is because of the extra pair of vocal folds above the throat. With this roar, the males claim territory, and during the mating season they attract females. The stronger this belch, the greater the chance of leaving offspring.