wait a few days, if he starts mounting them separate him, he is just maturing, thats all! its leaving mummy time for him! when he is about 5 months, try neuturing him to be with the girls, he wont be lonely then. the reason i chose this over getting him a freaind is cuz boars will grow up and fight 80% of the time, you could end up with 2 lone boars in the end! best to wait till he can be neutured and have him with the girls!
Please don't take this the wrong way Vi, but boars don't normally end up fighting, well not in my experience anyway, lol. I have more boars than sows and not one of them lives on their own ;D In the past five years I have only had one really difficult boar that wouldn't live with anyone. Neutering is a really good idea though as there is nothing better to see than a very happy boar, if you get my drift, lol. Just please remember that with any surgery there is a risk, even if it is a small one. Be sure to find a very compentent cavy knowledgable vet if you decide to neuter ;D