Ecology: how to compare "intrinsic growth rates" (r)

Hi everybody,

I would like to know how to statistically compare different "intrinsic growth rates", most of the times named "r", belonging to different populations.

It's a ecotoxicological experiment with these two simple variables:

1) time (days, from 0 to 21)
2) live offspring (total number on each day of the test)

I've calculated "r" with the Euler-Lotka equation for each treatment.
Now I'd like to be able to assess if one "r" is different from another.

Thank you so much, hope to hear a couple of ideas! :)