Housing multiple males. Yay or nay?
Updated: Nov 13, 2019
This is a long debate that has been gaining more and more weight over recent years. As a breeder, the answer I have found for myself personally? Is nay.
SO I know thats a big statement to put out there and thats just from a breeders perspective, and don't worry, I'm going to back up my reasoning for this.
Male mice are naturally territorial in the wild and single buck will lord over a harem of does. In the wild animals also have unlimited space (to a point), so external bucks have the opportunity to escape. But when we keep domesticated pets, yes, they are no longer wild but they also don’t have the opportunity to escape from other bucks. They may hold onto some of their wild instincts and no longer predators hunt them but as a natural prey animal, mice will still be skittish and evade being "captured" when we go to pick them up. In the same sense, male mice will still want to protect their territory and will do what they instinctively need to do.
Some people will argue that brothers from same litters can be housed together, yes this is the case in some circumstances, but isn't always the case. Often males can be housed with their brothers up until hormones start to gain more control over their bodies and natural instincts kick in, just because they are related doesn't mean that they will always "love" each other. In such circumstances, when owners have come to myself asking for mice and they mention they have brothers living together I will always warn them to make sure they have a backup cage at the ready as even mature bucks who are living together can turn on each other at any time, and in those cases, there's no going back to the way things were before.
The other argument is that there have been many cases of rescues neutering bucks and having success in integrating them with other neutered bucks. For me, this leaves me feeling uneasy. Hormones can take a long period of time to become balanced in the body (no matter how small the creature). Even after the healing period, theres still the risk of high levels of testosterone in their systems leading to ﬁghting and the risk of injury or death. Mice have a tendency to aim their bites to the base of the tail and scrotum, leading to skinning these areas and excessive bleeding.
If neutered males are to be introduced to a colony, I would think there would be a higher success rate with females over males, though a suitable time period should be waited to ensure that any residual sperm has died oﬀ to avoid unexpected pregnancies.
The other issue with neutering males is that a small rodent savvy vet would need to be located, and although the numbers are rising, still aren't readily available. Secondly, with all small rodents, they are a high risk under anaesthetic and theres a possibility that they may not survive or have issues post-op. Thirdly, the cost of the procedure and the aftercare would also need to be considered when thinking of neutering a buck. Although we aren't against neutering bucks, we would thoroughly recommend that you take these issues into consideration when you're making the decision.
Another option for giving male mice company would be to give them a companion in the form of an African Soft Furred Rat (ASF) aka Multimammates. These are gerbil sized rats that although would not come across mice in the wild, have had success in captivity of being housed with mice. Due to them being a diﬀerent species, impregnation is impossible and your buck can have himself a girlfriend that is double his size! The issue here is that introductions will be much more dangerous if the ASF is unwilling to take a mouse companion and is unimpressed by his lusty advances, due to their large size, can do a lot more damage to a mouse. Also it would be recommended if an ASF was the way you wanted to move forward with providing your mouse with a companion that you were to ﬁnd females to avoid territorial behaviour from both cage mates. While ASF are quite popular in the feeder breeder community, they are not so readily available in the pet market and so temperaments may not have been taken into consideration when they were bred, you would want to ﬁnd calm and docile ASF to be housed with mice for this option.
Lastly, theres the option to house a male alone. Yes I know that we have spoken about how mice are social creatures, but males in the wild may not come across females to create a harem and so would live their lives solitarily. The main thing to take into consideration would be to make sure that you provide continuing enrichment for you lone male mouse and ensure that he still has plenty of space to roam. Constant layout changes can encourage bucks to continuously explore their cage, scatter feeding to encourage foraging behaviours and suitably sized wheels to ensure that they are exercising enough and to discourage lazy behaviours noted with domesticated animals.
Although I'm sure there will be some of you who don't agree with this article, these are just the musings of a mouse breeder who has seen the good, the bad and the ugly of housing male mice together and what I wouldn't want to see again if I can avoid issues.