At what age is a male rat infertile?

Question

I have male rat that I keep with 2 older females. They are all 2+ years old, I am going to get a younger female today and was wondering if I am going to have a problem....really don't want to separate but might have to.

Answer 1

Do you mean fertile (able to breed) or infertile (not able to reproduce)? They become fertile at a very early age and need to be separated by gender at 5 weeks of age. They live to be 2-3 years old in captivity and as far as I know males stay fertile their entire life.

Answer 2

Well, female mice are infertile at a year of age, so a rat is about the same.

Answer 3

I really don't think there's a guaranteed age for elderly male infertility. There have been 70-odd year old human men who fathered children, and you really can't be sure your rat is infertile just because it's past the, say, two-year mark. Better to house the male with other males and not run the risk of surprise litters at the worst possible moment.

Edited to add: get him neutered (if you think he's up to it), quarantine him for three weeks - that's how long sperm can stay viable post-neuter - and you won't have a problem. But DON'T house him with females of any age unless he's been neutered. 2+ years is FAR too old to be having babies (and I've heard about rats still having litters at that age!). I don't imagine it would do your potential new girl any good to be pregnant at whatever her age is, either. Simplest, cheapest solution? Get a couple of new boys to keep your old boy company and have them in their own cage.

Answer 4

males can breed from the age of 5-6 weeks. so anytime in the first 5 weeks i'd say.

Answer 5

Get him neutered.  Male rats can reproduce from the age of 5 weeks until death.  Older female rats do experience menopause, but it can be difficult to determine when it has set in.