You must neuter your male guinea pigs. Guinea pigs are social animals that need the company of their own species. Unfortunately some guinea pigs are still kept without the company although it is cruel to keep them alone (DeKnegt 2012). So in order to avoid a population explosion, you will have to neuter the male guinea pigs if you are keeping a mixed sex group or a male/female pair. Neutering the male is easier for vets to do than spaying the female, but females can be spayed if necessary (Murray 2006). Neutering the male should also reduce aggression (Johnson 2009).
Johnson, D., (2009), Essential Exotic Companion Mammal Surgeries’,’ Association of Exotic Mammal Veterinarians 2009 Conference Proceedings, 57-63
De Knegt, S., (2012), ‘Welfare assessment in young pet rabbits and guinea pigs in the Netherlands,’ Dissertation Utrecht University, 1-67
Murray, M. J., (2006), ‘Spays and neuters in small mammals,’ Proceedings of the North American Veterinary Conference, 1757-1759.