guinea pig sexes

Question
the other day my sister just got a 'male' guinea pig, which they said they are absolutely positive was a male. so when we brought it home, we introduced it to my three year-old 'male' guinea. when we put them together, the younger one started jumping on Marcus and then they started making this weird noise. i never knew for certain if marcus was a boy because i got him from a freind when he was a baby. what should i do? and do u think marcus could be pregnant?

martha

Answer
If you have a female it could possibly be pregnant depending if it was in heat or not, females go into heat every 15-17 days. I put a website below that has a lot of pictures of male and female guinea pigs so you can sex yours easily. Usually 2 males will try to mate with eachother, but if one "male" stayed still while the other was trying to mate with it and didn't try to mount the other one then you most likely have a female. If you do have a female she will start to show in about 2 weeks if she is pregnant, the babies will start to move 4 weeks before they are due, and the gestation period is 68 days. Let me know if you have any more questions.
Brittany
Website-  http://www.cavyspirit.com/sexing.htm