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Guinea Pigs/guinea pig aggression


Hi, I've owned my pair of guinea pigs for about two weeks. We were told they are female litter mates. I am 12, their owner, and have been taking good care of them with the assistance of my mom. We let them out at least twice a day, and feed them lots of fruits and vegetables. They were doing okay until a few days ago. They have started being aggressive with each other. The larger one is trying to mount and attack the smaller one, the smaller one started peeing and spraying the other. We have them in separate cages now. Do you know what the problem is?

Take a good look at their undersides and see for sure that they both look alike. I can tell you for sure that the one doing the spraying is female. When a boar attempts to mate and the sow is not ready she will do exactly as you saw. She will arch her back and shoot a stream of urine directly into the boar's face. She never misses either. This usually cools his jets instantly and he will stop. However, he will continue to keep trying until he's successful.

If you do see a difference then obviously what you have is a boar and a sow. When a sow comes into heat, which is usually every two to three weeks they are only receptive for about three days, sometimes less. Even when two sows are together when one comes into heat they will sometimes mount their cage mate. This is just a hormonal instinct, but the sow being mounted rarely shoots a stream of urine at another sow.  

So to answer the question, there isn't a 'problem' per se, it's just that you very likely have a boy and a girl. If that's the case you need to keep them permanently separated unless you want babies.

If you're not sure whether or not they are male and female just send me a picture of their genitalia and I will tell you.

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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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