American Fancy Rat & Mouse Association

This article is from the Spring 1998 AFRMA Rat & Mouse Tales news-magazine.

Culling: Mice

By Carrie Ramson & Saga Baern, Finland

Culling, “the ugly c-word,” you name it. Few subjects in the world of mouse breeding raise such strong opinions as culling. It is even more so with rats. The opposers see culling as “humans playing God” and think wrongly that it is done so that the breeder gets “better animals faster.” This is absolutely not the case. There is no way that the babies are better (in any other aspects than health) just because they are from a culled litter. Culling does not affect the genetic make up of the babies in any way —only genetic engineering would do this. Culling does not make the animals grow bigger than their inherited factors allow. Proper diet of the mother and the babies all through the period of their growth play a great part in this as well.

Why Cull?

The real reason for culling is the love of animals. If you do not cull, the nature will do the job. Only the nature is cruel. The babies will not die peacefully in their dreams—they have to struggle for survival and the weakest ones do not manage. They will die a slow, painful death out of malnutrition and if they do survive till weaning age, they will suffer the same problems as humans who have suffered from malnutrition in a young age—both physical and psychological. Bloat is one of these problems.

When a female mouse has babies, she can have 10–18 young. This is because, in the nature, the mouse is prey for many animals. Only a few babies survive to be 4 weeks of age, even if there were well over a dozen in the litter.

When humans have taken mice to be their pets, provided them with warm and safe abodes, the culling of the babies is their responsibility. If all the babies were left for the mother to take care of, every one—the mother and the babies—are in danger of dying. Eighteen babies is simply too much for the female’s 10 nursing nipples. There is not enough milk for all the babies, or enough energy for the female to take good care of all her young. The breeder, who breeds her mice, has the responsibility of the welfare of her animals.

Harsh Reality

If you do not cull, you have to face unpleasant facts. It is very possible that the mother will die of over exhaustion. This is something many beginning breeders have had to find out the hard way, as well as those who haven’t even heard of culling. Culling is not about gaining a God-like power over mice and getting a “supermouse.” It is about harsh reality and love for mice. No one wants to see her mice suffer.

Few subjects in the world of mouse breeding raise such strong opinions as culling.

Recommended Way Of Action

The number of babies you leave with the mother depends on the situation, but the suitable number is considered to be 2–6 babies per litter. You have to know (or estimate) how many babies the mother can successfully nurse and her capability of taking care of the babies. You also have to think of how many babies you can provide with a good home. You should do the culling before the babies reach one week of age. You don’t have to cull all the babies to be culled at once, but in two separate occasions. If there are really huge amounts of babies, this is the recommended way of action.

Put the female and her food bowl into a travel box before removing any babies from the nest. Start by choosing from the weakest and smallest of the babies, and from those who have missing body parts. These individuals have lost the fight called “who can beat the others at the dinner table.” Their development into balanced individuals has been shaken and malnutrition weakens these individuals even more. The main idea of culling is the removal of the weakest and the most ill-fated; the healthiest and strongest ones are left in the mother’s care. You should also check the sexes of the babies. Males try to get their share and more of the milk much more aggressively than the females, thus straining the mother more than females do.

Ask For Advice

The most unpleasant phase in culling is putting the babies to sleep. This article does not discuss the proper methods, only that the method must be quick and as painless as possible. Drowning or feeding the poor babies to reptiles are out of the question, as these are slow, horrible deaths. You can ask for the proper method, help, and advice from long-time breeders.

Breeder’s Responsibility

When you are thinking about having babies from your female mouse, consider very carefully: are you able to think about things from the aspect of your mouse. Human beings think largely with their emotions, but they are unable to put themselves in the place of the female mouse and the suffering babies. No one likes culling, but a breeder who loves life and healthiness must take well care of her friend, the mouse.

The responsibility of the mother’s and the babies’ well-being is on your shoulders!! The babies exist only because you wanted them—do not breed a single litter if you are not able to carry your responsibilities to the end. *

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Updated March 20, 2014