Densest fur (land animal)

The terrestrial animal with the thickest fur is the long-tailed chinchilla (Chinchilla lanigera), a rodent native to mountainous regions of western South America. Each of its follicles can produce between 50 and 80 fine hairs, with up to c. 25,000 hairs per square centimetre (161,000 hairs per square inch) where the coat is thickest on its rump.

The chinchilla’s thick pelage has evolved to be an invaluable survival asset, keeping it insulated in its native Andes Mountains where temperatures can reach sub-zero levels in the winter months. It also helps to protect it against pests such as fleas, as the fur is so thick that parasites struggle to penetrate it without risking suffocation. On the flipside, chinchillas are very vulnerable to heatstroke in temperatures above the mid-20s Celsius, plus they favour bathing in dust rather than water as getting soaked through requires many hours to dry off, which risks disease or fungal infection.

The animal with the densest fur overall is the sea otter (Enhydra lutris), with around 100,000–160,000 hairs per cm2 (650,000–1.03 million hairs per sq in). Sea otters live in colonies in the north-east Pacific, off eastern Russia, western Canada and western USA (particularly the coast of Alaska).

By comparison, on the human head, the density of hair averages 120–200 hairs per square centimetre (800–1,300 hairs per square inch) and each follicle produces a single hair. Among domestic dogs and cats, the greatest hair density tends to be around 20,000 hairs per cm2 (128,000 hairs per sq in), though this may creep up close to chinchilla levels on the underbelly of some of the furriest species of cat such as Maine Coons.