Perhaps one female is marking the others as a sign of domination? Ive certainly never heard of this in geckos but, hey, anything is possible
:I have never personally seen it myself, but I have heard of it happening on one other occasion (gex-anonís geckos). Why it happens, who knows (I know it also happens with livestock on occasion). As for the sperm are you sure thatís what it was? Maybe you mistook it for urates?