Lone Males

Whether or not male mice should be kept on their own is somewhat of a controversial subject. Common opinion seems to be that they should be kept alone, as being notoriously territorial they will often fight bitterly if kept together, but there are also those that believe that an animal as sociable as a mouse should never be without others of its own kind. I believe both are true. In the wild male mice do not usually share their territory with other males. Each male has their patch and female mice (and the resulting babies) will live in their own spaces within it. A male will fight any other adult male who comes into his territory in order to keep them away from ‘his’ female(s) and therefore guarantee that he will be the one to mate with the female and pass on his genes.

Bearing in mind that this is the natural way for male mice to live we can see that they are ‘programmed’ to want to both fight other males and live in a group and even though our mice are now far removed from their wild counterparts it seems these instincts largely remain. This causes many problems when it comes to pet mice, as obviously responsible owners want to keep males and females separate, so the question that arises really is whether there are circumstances in which males can live together without fighting.

Many articles I’ve read suggest that males who are related (ie father and son or litter mates) are more likely to get along. Going back to wild mice this would seem to make sense as a father is not as likely to feel threatened by an immature male as he will not be competition for the females in the same way a fully grown, mature buck would be. The other things that seem to come up most consistently is the size of the cage they are kept in and the number of bucks in the group. It seems that providing male mice with more than adequate space allows them to have their own territories if they so wish and can give them a much better chance of remaining together without fighting, as does keeping the group size small (aggression levels have been shown to be higher in groups of males larger than five).

However for every one person who manages to keeps males together without fighting you’ll find several who can’t - even by taking into account the above circumstances - which is why a lot of people believe that they should be kept alone. If we go back to the natural behaviour of wild mice though you can see that whilst males don’t usually share their territory with other males they nonetheless live in colonies and so it very unnatural for them to live alone - see the article ‘Why mice need company’. Lone mice of either sex can quickly become depressed which in turn can have a detrimental effect on their health - in fact laboratory experiments have shown male mice to prefer the company of another male over the option to live alone, as the further reading links below show. With all this in mind I have vowed to never again have a mouse live out its life alone and where males are too aggressive to live together I now have them neutered.

Further Reading:

Mouse Behaviour from the US Humane Society Website (scroll down past mouse biology)
Behaviour In The Mouse by Eva Johansson
Kinship And Social Behaviour In Wild House Mice by Jane L Hurst & C J Barnard
Hormones In Context: Mice and Rats by Jed Bland
Do Male Mice Prefer Or Avoid Each Other’s Company? by Pascalle L. P. Van Loo & Associates