[Cazador]

Hi Cyrill,
Pardon me. Reptiles don't make urine from their kidneys (like mammals do) and don't secrete ammonia (like amphibians and fish do). Instead, they make white crystals called "uric acid" as a waste product from their kidneys (like birds do). It's a way to help them preserve/conserve water. The uric acid is often mixed with moist, or even wet, feces (poop) in their cloaca, which often makes the waste product moist.

Basically, when your snakes are active and they poop, there is a white part and a brownish part. The white part is uric acid, and the brown part is feces (poop). When your snakes are brumating, they don't poop. They only release the white uric acid. It's the white part on the rocks.