Very Horny Guinea Pig

[Looby]

We recently took in two boars. We think one is around 6 months and the other is 1 year. One is a long haired breed so we obviously want to brush him regularly. We haven't noticed any negative behaviours between the two. However we have noticed every time we get them both out to brush, the long haired one gets what can only be described as very horny. He starts rumbling and rubbing himself. He will try to mount the younger one and this will continue for a while even when placed back inside the cage. Obviously we know hormones will play apart but the only time this happens is when he is being held by us and brushed. Its obviously not very nice for the younger one too. We don't want to separate as there isn't any aggression and it only happens when they are being held. They were housed together when taken in so its not a new pairing. Has anyone else noticed this behaviour?

 

[Swissgreys]

This is perfectly normal boar behavior, and in fact also pretty common in girls.
Rather than being sexual it is about dominance, and reminding the younger boar just who is in charge when they are put back into their territory (the cage).
It is nothing to worry about.