Grooming claw

Close-up of a ruffed lemur's foot, showing the toilet-claw on the second toe and nails on all other toes

A toilet-claw (toilet claw, grooming claw) is the specialized claw or nail on the foot of certain primates, used for personal grooming. All prosimians have a toilet claw, but the digit that is specialized in this manner varies. Tarsiers have a toilet claw on toe two and toe three. With one possible exception, in the suborder Strepsirrhini, which includes lemurs, galagos and lorises, the toilet claw is on the second toe. The possible exception is the aye-aye, which has claws instead of nails on toes 2 through 5. There is some debate concerning whether any of these claws (and if so which ones) are toilet claws.

The first toe is the large one, the equivalent of a human big toe. However, in all these prosimians the foot is more or less hand-like. The first toe is opposable, like a human thumb, and the second and third toes correspond approximately to the index and middle fingers.

Like a claw or a nail, the toilet-claw is also made of keratin. It resembles a claw in both its lateral compression and longitudinal curvature. However, the tip is not as pointed, and it always stands at a steeper angle, a characteristic that also distinguishes it from a nail.

Etymology

The term for this prosimian anatomical structure comes from its function, which is to assist in grooming or toilet functions. The term toilet, as used in American English, has changed over the past century. Historically, it was used to refer to personal grooming, not a lavatory device. Due to changes in the perception of the term, some sources have started to use the term grooming claw instead. However, the scientific literature still strongly favors the original term.

Function

The toilet-claw is used in personal grooming to rake through the fur, particularly where an individual cannot reach with its mouth and toothcomb.