(This question is aimed at animals that take care of their young, e.g. dolphins.)
As I understand it, most animals reproduce if possible. The only way they don't is because they run out of resources. I'm wondering how this shows up in practice:
- Do they simply not have sex? If so, does this mean they don't have sex drive?
- Do they conceive and then let their children starve to death?
- Do they fail to conceive (that is, are there biological changes to a mother who's not getting enough food such that she is no longer fertile)?
Option #2 seems the least likely to me because presumably pregnancy involves a cost to the parent, and with resources already scarce this would be a waste; however the plot of White Fang does indeed involve this situation (I have no idea how scientifically accurate that book is however).