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Guinea Pigs/Bonding/Aggression


Hello!  We recently adopted two 8 month old "bonded" male guinea pig brothers, Jim and Jack, from the humane society.  They were in the same cage when we visited, and adopted them a week later.  When we first brought them home, we put them in the same large cage with no issues.  About a week later, when they were outside of the cage and playing inside a large box in their play area (we were cleaning the cage), they started fighting.  Jim tore the Jack's lip (it's been sutured). Since then, they have been living in separate cages (side by side) and have been neutered.  It's been 10 days - we take them outside while cleaning their cage, they have free roam of a large backyard (carefully watched and provide them each "shelter"; however Jim will seek out Jack (who has taken to hiding more in his igloo) and Jack will Chatter aggressively. It's only happened twice since surgery that they've had "access" to each other.  I switched their cages today, and Jack continues to "chatter" aggressively.  I plan on building them a C/C enclosure, but am really concerned about the behaviors.  Please advise how best to re-introduce them to the same space, when to do so, and if putting a barrier separating them in the C/C cage (I saw one set up on a C/C cage design website) is a good option or not.  I am following advise on fresh veggies/fruits, they have unlimited access to Timothy Hay and water, using Oxbow pellets, have apple wood sticks for chewing, both have igloo-type shelters, cardboard tubes and such for play/chewing.  Sorry so long, thanks for your help!

My apologies for not being able to write sooner. I have not had Internet access until now.

Most boars, even those who have grown up together, reach sexual maturity at about 6 to 8 months of age. They become territorial and aggressive, not because they're unhappy but because they are driven by hormones.

All herding animals go through this part of their lives. As long as there is no drive to breed they will get along, but as soon as the hormones kick in they instinctively start behaving this way and fighting to determine who will be the king.

There isn't anything you can do to change this. They are hard wired by nature to listen to their hormonal drives and instincts. The safest thing you can do is keep a barrier between them. They'll be fine even if they can see one another and touch noses. But put together they will continue to fight until one or both of them are seriously injured.

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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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