Old sperm is bad news. The longer it is stored in the testes, the lower its quality. And offspring created from older sperm can suffer detrimental health impacts.
In order to understand how sperm quality changes when there is little or no sexual activity, researchers have been analyzing the sperm of house mice.
They compared those which had not been sexually active for about two months to those which had a much more recent sexual encounter.
It came as a complete surprise to the team that the sperm quality of these two different groups was the same.
The mice are able to keep sperm quality high by using a number of tactics when they have no access to a mate. These include spontaneous ejaculations and losing sperm in urine. There may even be molecular ways of keeping sperm young to protect it while in storage.