The Surprising Math of Spay & Neuter

Added: 2026-05-27

[00:00:00]If you put 10 unaltered male dogs in a big yard with 10 unaltered females, soon enough you will have 10 pregnant females, right? But if you were to neuter nine of the males and leave only one intact male among all those dogs in the yard, how many litters would you have then? Still 10, because that single unaltered male would happily sire litters from all the intact females. So in this example, your nine neuter surgeries have no effect on births. But what if you switch that? What if you left all 10 males unaltered, but you spayed nine of the females? Then how many litters would you have? Only one.

[00:00:37]Strictly speaking, the number of litters in a population isn't dependent upon the number of unaltered males, but it's dependent upon the number of unaltered females.