The Lizard Detection Stone is an item gained through beating eight colossi on Normal Time Attack or 10 on Hard Time Attack. It is a small, golden statue of the lizards that inhabit the Forbidden Lands.
Dormin says the following upon retrieving the item:
|“|| That is the 'Lizard Detection Stone'...|
By using it, thou shalt be able to find the lizards throughout the world...
This stone shows the location of white-tailed lizards in the immediate area around Wander. They show up on the map, but the lizard's elevation will not be shown. Finding the lizard takes careful searching, because it could be right behind a wall or hiding in some bushes. The symbol disappears when the lizard is killed, but not when the tail is pulled off by shooting at only the tail. Therefore, although more merciful, it is not a good idea to shoot the tail off of most lizards.
Like the Fruit Tree Map, it isn't an item that is required to carry, rather equipped and activated on the map.