My housemates have 6 adult guinea pigs. They have free rein of the backyard along with some chickens and a small dog (who doesn't harm the guineas btw). The adults run around free and they retreat to a large shed with an area for them to shelter at night (floor is just dirt though, no hay, not sure if that's ok?) and we close the door in case of predators. There seems to be a clear leader in the "pack". They are all females.
I got a new baby piggy (female) and I am worried it's too small to just be put with the others so not really sure what to do with it.So far it's sleeping in a box with food and water and blankets, towel on the bottom). I placed one adult with it overnight in the box it's been sleeping in and although it nudged it with it's nose at times, they cuddled up and seemed happy. However when I put the "leader" with the baby the baby froze and the leader just grinded it's teeth a bit so I took it out straight away.
The adults are not tame. They are ok once picked up but the housemates almost never touch them so it's hard for me to "catch" them to put with the baby.
I'm worried it's lonely! Its so tiny though...could i just put it outside or will it die or get cold or get bitten by the others? It "purrs" when I pat it sometimes but I can't tell if it's scared or likes it as it shivers or vibrates sometime too at the same time!

Help!