The Southern Cape Bunny Haven have some huge sterilization runs coming up!
Next week, we have 8 girl bunnies  and a boy bun; as well as the 3 foster Guinea Pigs that needs sterilizing.
So,  when and why do we steri? All males get sterilized after their testes have dropped; at about 12 - 15 weeks.    The little ladies wait longer; and even though they can fall pregnant by 15 weeks; we steri them at about 22-25 weeks.
It is important that males that is fertile and females must be seperated. Males that had the operation done, is fertile for up to 4 weeks after the operation.There is enough hurt and discarded bunnies in the world - by sterilizing; you help stop more bunnies from being hurt or discarded.
Sterilizing stops some of the behavioural problems as well. Both males (bucks) and females (does) will spray urine when unsterilized; or hefore their hormones have fully settled, which is 8-10 weeks after the procedure. 
Sterilizing females (both rabbits and Guinea Pigs)  are not only about stopping babies..but also to protect them from 2 very harmful illnesses.Uterine cancer: females is very susceptable to uterine cancer; esp from the age of about 4-5 years.Piometria - meaning a pussfilled uterus, due to hormonal changes eg in false pregnacies amongst other; can quickly lead to septicemia and death. 
If you live your bunny, sterilize! And also to stop more babies; sterilize!