A mammal that chirps
In the dense rainforests of eastern Madagascar lives a creature that challenges simple categorization. The Lowland Streaked Tenrec (Hemicentetes semispinosus) is a small mammal, about 14 cm long, with the spines of a hedgehog and the black-and-yellow warning stripes of a bumblebee. But its most unusual characteristic is audible only to specialized equipment: it communicates by rubbing parts of its body together, a method known as stridulation. This makes it the only mammal known to use a form of communication more common among insects and snakes.
The tenrec's unique sound-producing organ is a small patch on its mid-back containing a cluster of 7 to 16 specialized, non-barbed quills. These keratinous quills are arranged in three rows. Beneath them lies a disc of cutaneous muscle, about 16.8 mm long in an adult, which vibrates the quills. When the tenrec contracts these muscles, the quills rub against each other, creating a series of high-frequency chirps and clicks. These sounds are largely ultrasonic, meaning they are too high-pitched for the human ear to detect without the aid of equipment like a bat detector. This silent chatter is constant as the tenrecs forage, likely helping family members stay in contact within the dense undergrowth.