Almost all mammal penises have foreskins or prepuce, although in non-human cases the foreskin is usually a sheath (sometimes called the preputial sheath, praeputium or penile sheath) into which the whole penis is retracted. In koalas, the foreskin contains naturally occurring bacteria that play an important role in fertilization. In some bat species, the prepuce contains an erectile tissue structure called the accessory corpus cavernosus. During musth, a male elephant may urinate with the penis still in the sheath, which causes the urine to spray on the hind legs.