House Rabbit Society headquarters has much to celebrate this year, as the day before World Spay Day they open their very own monthly spay/neuter clinic in conjunction with Fix Our Ferals. Community low-cost clinics like this are so in need. Some communities have a clinic, but they do not cater to rabbits but instead do cat or dog only (such as the one in my community). That's a shame! Because, as you know, if left to nature rabbits will breed... well, like rabbits!
Why are bunnies so darn fertile? Mother nature has given them a few advantages in the breeding department. Female buns don't have an ovulation cycle like most female mammals do. Instead, it's the act of love that triggers their ovulation. Essentially, this almost guarantees their success at becoming pregnant.
A bun's gestation period is 28-31 days. Each litter averages about 6 little baby buns. Given how they ovulate, a mama bun can find herself pregnant almost immediately after giving birth. So doing the math... if you start with one single pair of rabbits and, barring any other pressures, just let nature take its course, you could have 1369 rabbits at the end of two years! Yikes! (I admit, I didn't do the match, as Dana Kremples had already done it so well!)
But even for your single solitary house rabbit, spay/neuter will help protect them against cancers of the reproductive system, which are common in animals as they age. The simple surgery can also have important effects on behavior... which think about it -- would you want to be single but driven by your biological urges for your whole life?