Yes, because if you just want a playmate for the boar (boy) and it's a sow (girl), they will breed and keep on breeding until the sow gets tired. And there will be hundreds of baby guinea pigs which will be too much to handle. So unless you want to breed them (only a few times) then you don't need to, but if not, keep them FAR away. Keep boars in a separate room from sows because if they are in the same room, the boar will smell the sow and try to get to her, and if there are two boars, they will fight until there is serious injury or sadly, death.
No. Most guinea pig cages are cat safe. If the cage is enclosed your guinea pigs should be fine. It is safest to have a latch though just in case.
it is good to have 2 guinea pigs because the first guinea pig can get lonely during the day if no one is around. If you have had one female guinea pig for about a week or two and have seen that she is getting lonely, you can put another female guinea pig right in the cage. If you have had a boy guinea pig for about a week and want to get him a friend, unless you want to have babies, get another boy guinea pig but keep them in separate cages unless you are monitoring them because boys will fight. If you want to have babies and you have one guinea pig, don't put them in together right on the spot because the boy guinea pig may get very aggressive with the girl to a very dangerous and tragic point. Keep their cages close together and once a week, hold them both in your lap (together) and pet them with the same perfume. If you do this, they will see that they have something in common. After about a month, put them together. if they look like they are in a dangerous situation, separate them again and do the same thing for another month.
It depends on the size of the cage.Some cages are cheaper when they come in a guinea pig care supplies kit.My cage for my guinea pig was $50.But, then again,it was originally meant for two guinea pigs.
No, only girls get pregnant :)
Girl
if they are drawing blood, biting, scratching, hurting each other you need to separate them in different cages. Each guinea pig needs 7 square feet of room. 2 pigs need 8 square feet.
Only the guinea pig she mated with but be sure to separate them after birth
Yes and fast
C & C grid cages. ITs a home pet.
No the guinea pig will no get pregnant.
Boy guinea pigs don't have nipples.
If it was a boy guinea pig - yes.