At my job, asa lab technician, I work with mice all day. Through observing them, I have come to realize that there is indeed a natural law in effect here on the earth. There are universal truths that manifest in the behaviors of mammals both great and small.
Universal Truth #1) Being by yourself will make you go crazy. People need people. No man is an island. This is obvious when I look at how loneliness and lack of companionship makes people become fearful and unhappy. Mice that are put into cages by them self become so terrified of humans that they will often jump out of the cage to flee. Being alone makes mammals neurotic. Having friends, taking lovers, touching and grooming and eating and communicating together makes for an excellent healthy and happy life. Mammals are meant to be together. Cages that have 2 mice or 3 mice in them are ideal, which brings me to the next universal truth.
Universal Truth #2) Having 2 mice in a cage has proven itself to be the most harmonious. This doesn't suprise me at all. It takes two to make a thing go right. It's the balance of ying and yang. A cage with 2 mice provides companionship for both but leaves up a lot of room for them to roam around. There is peace and quiet and less pollution for them to deal with, so both mice benefit on all levels. They have a higher quality of life. This princaple is also applicable to humans, as studies show married couples are ultimately the happiest. It's when 3 or more mice are introduced into the cage environment that trouble begins.
Universal Truth #3) Three is a crowd. Monogamy works best because it is sustainalble. One man getting two ladies pregnant is not going to work because thats too many babies and pressure and it makes the woman compete for the males resources. It just creates a scenario where everyone is spread thin and the ones that suffer the most are the offspring because the more offspring there are at any given time the more likely some will be ignored and die off or at the very least live a miserable stressed existnece. So there is a reason why threesomes break up marriages. Infact, it is just natural law in effect. We revolt against what is inherently bad for us.
Mice that are put in these harem breeding cages, 1 male with 2 females, have higher instances of neurotic behaviors such as chewing each others hair off. This is when the most dominant mouse in the cage plucks hair out of the other mice and leaves bald patches. It's the mice's way of saying "You know what? I'm tired of you being on my space all the time, now I'm going to fuck with you a bit". It's usually one female doing it to the male, or doing it to both the male and rival female. She is exacting some kind of revenge perhaps. It's like she is saying fuck you to the male for being a cheater and to the other female for trying to steal her man away. Both are factors that would jeopardize her offsprings survival. I have even seen females fly into murderous rages where they canabalize the rival female.
Next time someone suggests a threesome, think twice, no good can come of it