Fibonacci series and rabbits

Did you know....
1. If you start with 1 male and 1 female rabbit.
2. They mature and reproduce at 2 months.
3. Just say that they only have 2 rabbits per litter (1 female and 1 male) (we know this is VERY conservative).
4. They can have a litter each month.
5. Just say no deaths occur.

Did you know that the number of rabbits you will have each month is the Fibonacci series? 1,1,2,3,5,8,13,21,34,55,89,144,...

After 12 months you would have 144 rabbits?! And that's if they only have litters with 2! How often does that actually happen?

Does anyone else find this interesting? My husband thought I was a little quirky but hey, he bought me the book! (Asimov on Numbers).

Maybe I find this kinda funny because 10 years ago we bought 2 immature rabbits - thought to be 2 female rabbits. "Thankfully" one got sick and they had to be separated until it was well again. In the meantime we discovered the healthy one was a male. Good thing we kept them separate!