ok, so last month i took in two guinea pigs from a friend of mine who could not keep them any longer. these are my first guinea pigs, ive researched there care but i now have a major problem, maybe. so the girl i got them from said they were both female, but one of them is like twice the size of the other one. she said that the little one was a runt and thats what was causing the size difference. she also said she has had them for 6 months. when i got them they were in a reg. store bought guinea pig cage that was super tiny so i built them a bigger temporary one. yesterday i added on another part of there cage, its about 6ft long and 2ft across and just now ive noticed the bigger one mounting the smaller one and making the purring noise. i know that sometimes the girls do this to each other to display dominance but im also very worried the girl i got them from lied to me somehow. since i just got them they arent really liking the idea of me picking them up to check their sexes just yet. is it at all possible that a male and female guinea pig could of been kept together for 6 months without mating? like maybe since they were in a small cage they were able to get in the mood. and does anyone have any tips on how to get them to let me pick them up so i can try to sex them?im sorry if this is a really dumb question but im throughly worried about this, thanks in advance.