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Guinea Pigs/Aggresive behavior


Hi, I got a guinea pig in Feb this year (Guinea) and I recently got another one so he wouldn't feel lonely when I couldn't give him enough attention. The latest one (Houdini) was small and they got along fine for some months. Now Houdini is older and bigger and just a moment ago Houdini started displaying aggressive behavior towards Guinea. He was nipping his butt and they reared up at each other and then Houdini started chattering his teeth and they both leaped at one another. I jumped up and intervened but I'm worried they will continue with this and I won't be there to stop them and they might hurt one another. I don't know if they would have started drawing blood if I hadn't stopped them. Should I separate them or will they work it out on their own?

What is happening is Houdini is reaching sexual maturity and is driven by hormones. Would they have drawn blood on one another, absolutely. You need to separate them and leave them apart.

Don't ever put your hand in harm's way by trying to break up a fight. The best way to break it up is using a garden glove. Don't put it on your hand, just grab it by the end and smack them on the head to get their attention away from each other. I don't mean to try to hurt them, just pop them with the glove and it will break the fight. One or both of them may turn their teeth to the glove, which is why you don't want it on your hand.

Guinea pigs are herding animals, and like all herding animals they run on instinct. This applies to any herd of any species. The herd consists of primarily females. The only males allowed to stay are the young ones that need their mother and have not reached sexual maturity.

The alpha male maintains breeding rights to the herd of females. In some herds or packs such as wolves, there is only one alpha female that is allowed to breed. This prevents inbreeding. With guinea pigs the only males in a herd that will be allowed to remain are those who pose no threat to the alpha male.

Once a youngster starts maturing and his hormones begin to kick in he will start to challenge the alpha male. This applies even though there are no females present. They start to fight over breeding rights. If the old male maintains his status the younger is banished from the herd. If the youngster wins the battle the old one goes away. That's just the way nature has made them.

They are hard wired for this behavior and there are only rare exceptions:

Old males that have passed their breeding age will accept a younger one without a problem. Again, it's only because there is no challenge.  In your case you have two males that are still going to battle over the females, even though there may be no females present. It's just a hormonal reaction and not something you can change.

Chattering teeth is a warning that a serious fight is imminent. The fight may end in the death of one or the other if not broken up. Serious wounds end up in bad infections. The only choice you have is to keep them apart. You can put their cages side by side, but you cannot allow them to be in the same cage together. As long as there is a barrier between them they will be happy.

I hope this answers your question.  

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Pat VanAllen


As is sometimes the case, people in urgent need of information have a higher degree of expectation than those of us as experts are able to give. The experts on this site do their best to give the most accurate and responsible answers possible. We ask that you remember that it is not our intention nor place to criticize the professional advice given by your veterinarian, nor is it appropriate for us to comment on the correctness of a diagnosis made by a licensed physician. Our knowledge is experience based. Although many years of breeding and showing cavies gives me a wealth of experience it cannot change the fact that we as experts are not veterinarians and therefore may occasionally have to reject questions that appear to be asking us to criticize advice given by the licensed professional. Having raised and exhibited cavies for many years I have extensive experience in cavy care and husbandry. I currently have an active breeding program for pedigreed show animals but do not encourage backyard breeding for inexperienced owners. Although I don't encourage breeding for fun I'm always happy to answer any questions from an owner who is in sincere need of help. Pet owners wanting to breed should understand that even experienced breeders have litter losses. The mortality rate is high in cavies. The chance for losing both sow and pups is always present, even with experience. Although this is a site for experts to assist owners, there is no expert in any field who has all the answers. The wisest thing a good expert can know is their limitations. Not having an answer does not diminish one's ability or knowledge. It simply shows that we recognize our limitations and operate within them.


Raised and shown cavies for many years, having aquired my first cavies in the early 1970's as pets. My caviary currently handles 65 + animals in two different breeds and several varieties. Having been in the health care industry as a licensed nurse for 35 years I have hands on experience with care and needs in both humans and cavies. Member of American Rabbit Breeders Association and American Cavy Breeders Association.

Awarded Lifetime Membership in of one of the oldest cavy clubs in the United States, on whose Board I served as Sec/Treas for six years and currently serving as President. Also editor/publisher of the club's quarterly newsletter. We are strong supporters of our youth exhibitors, most of whom are 4H members who are working on cavy projects. Through these projects they become good responsible citizens. We deal with all aspects of showing, breeding, caring for and sharing experiences in the fancy. The cavy fancy is not a new one but in some areas is still relatively unknown. Our goal is to inspire interest in high quality, responsible breeding to improve the species, not just the reproduction of guinea pigs. Our job is to educate owners to help them make the right decisions and choices in the care of their cavies.

Graduate in nursing. Certified in emergency medicine.

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