My guinea pig is 9 months old and she is loosing hair around he butt what should i do?

Question

bare in some spots and their skin is usually blackish right?

Answer 1

Sounds like mites. Get treatment!!!

Answer 2

Hairloss in Guinea Pigs is usually either due to fighting or mite infestation. Mites usually leave random bald patches where your piggy has been itching and has a dandruffy appearance on the skin. Take her to the vet who will give her a course of injections to free her of these microscopic itchies!