Is nest building learned or biological?

[Oxylepy]

If a rat or a mouse were given no substrate (this is hypothetical, I'm not actually doing this) and left in a plastic tub, then gave birth, incapable of making a nest, and you were to do this for a few generations, would the future generations still try and form nests if given substrate or would it be bred out of them?

[snakesRkewl]

Good question, I'd guess that it would take more than just a few generations to remove something so ingrained into their mentality.

[Oxylepy]

But the question is more is it ingrained in their mentality, or is it ingrained in their biology? Do they have some kind of instinctual need to build a nest, instinct would require selective breeding, not just exposure to the situation. But if it isnt something so base then perhaps a few generations of random breeding of rats who have not been exposed to nests should be adequate, but if it's biological a whole hundred generations could go by and they would go right back to it when given the chance.

[JayCee]

I would vote instinct. There is no "nest" still around by the time the babies have their eyes open, but first time mothers always do it.

[xdeus]

Instinct, but I think good mothering is a combination of instinct and learned behavior. I've had mothers which were completely clueless about raising their young if they weren't exposed to another mother rearing her young.

[theturtlepond]

Depends on what you consider a nest. Some of mine don't really build a nest they just pile the babies on top of the bedding and the babies kind of make a hole in it.