How can you tell if a horny toad is a female?

There are several ways to tell the difference between males and females, though you may not be able to do so until they are older (at least by several months). Be warned. Unlike with other species of lizards, size is not a recommended way to tell the difference in sex with these animals. First, you will want to check the underside of the lizard's body, but be wary not to tip the lizard upside-down. Most lizards cannot breathe like this, and it can easily collapse their lungs and kill them. When you can see their belly, you're going to want to check the pores on the upper leg and stomach. The pores are big on males, and extremely small on females.

Second, look just below where the legs and abdomen connect on the belly. You are looking for the hemipenal bulge. This bulge will be slightly puffy on a male, and will not be there at all on a female.

Third, both species have a slice across their abdomens, called a vent. This vent is visible on a male's body, but, again, almost non-existent on a female's.

Finally, check their tail size. Males have a larger tail with an almost heart shape to it. A female's tail is smaller in size, with a triangle shape.