What is this?

Question
Hi!
My female guinea pig (her name's Cookie)has a nipple that's kind of blackish and 'hardish' but the other one is pink and looks really healthy... Why is it black?

Answer
Hi Michelle,

    I honestly have no idea why it is black and hard, although sometimes the nipples may be colored differently depending on how the pigmentation is genetically expressed.  If you really feel that this is a hindrance to his health and makes him at all uncomfortable, it would be best to contact a veterinarian who is experienced in the area of guinea pigs for a proper examination and diagnosis.

    Thank you for your question, I hope I have been of some help to you.  If you have any further questions, please do not hesitate to ask.  Good luck with your guinea pigs (=

                                              - Nicole