There was some talk about this but I searched and can not find it? It looks like Gulliver has some black heads on his tail. Sphynx getting them on their tail or around their mouth is not uncommon. Athena gets some around her mouth and I pop them (can't help it). I know someone had said to clean the tail with A stridex pad, they said that it helped get rid of them.
Gulliver, this is known as Stud Tail. Using Stridex pads on it twice a day will keep the blackheads at bay. This is caused by an overproduction of sebaceous material produced by the skin, bathing more frequently helps too. Intact male cats are most prone to this and its thought to be secondary to testosterone levels (therefore more likely when the males are around females in season...which may be inside or outside of your home).