Butter Royal Pythons
A royal python with a Butter gene has its melanin reduced and yellow lifted to create soft yellow markings over a ground of caramel or tan. Because you cannot tell it from a Lesser by eye and the two are still sold interchangeably, only a genetic test tells you which gene an animal carries.
- Super Butter (aka Blue-Eyed Leucistic (BEL)) — linked to eye deformities, including bug eyes - a protrusion of the eye
- Butter — do not pair with another Butter or a Lesser. Offspring of that pairing carry a hereditary defect.
About the Butter gene
The Butter gene lightens a royal python (ball python). It lifts the yellow and reduces melanin, leaving a caramel or tan ground with soft yellow markings. Because two copies make the Blue-Eyed Leucistic, many BEL projects include Butter. You cannot confirm it by looking at the animal, and for a buyer, that is what matters most of all.
Appearance
Butter snakes have a royal pattern and a caramel-tan base with soft yellow markings. Since they range from pale creams and browns to rich tans and yellows, no two Butters need look alike. A Super Butter is a Blue-Eyed Leucistic, which is a white snake with blue eyes.
It is not possible to tell a Butter from a Lesser with any reliability. They behave the same way in combinations and look extremely similar. Seeing the snake in person or looking at a photograph will not settle which gene it carries.
Genetics
Butter is an incomplete dominant. One copy shows as a Butter, while two copies make the Super Butter, the BEL. Because it behaves in the same way as a "co-dom", many breeders still use that term, though it is less precise. There is no het Butter.
The Butter belongs to the Blue-Eyed Leucistic complex. This allelic group also holds Special, Mocha, Russo, Phantom, Mystic, Lesser and Mojave. A BEL is also any animal carrying Butter plus another member of the complex, including Lesser.
The hobby treated Butter and Lesser as one gene with two names for years. Different breeders in different lines found them, but the Butter came from a wild-collected bloodline. They are distinct genes in the same complex, as testing by Rare Genetics Inc (RGI) in May 2025 showed. Because the hobby still sells them interchangeably, a Butter that is untested might be a Lesser, and a Lesser might be sold as a Butter. To know for sure, a genetic test is available and is the only way. Mark and Kim Bell of Reptile Industries proved Butter out in 2001.
Known issues
A single-gene Butter carries no welfare note. The two-copy Super Butter (BEL) is linked to eye deformities, including bug eyes - a protrusion of the eye. BELs made from a Butter and a Lesser carry the same tendency even though Super is not in their name, so treat a Lesser Butter the same way. Every Butter listing carries breeding guidance against pairing it with another Butter or a Lesser, because those are the pairings that make these animals. Severity varies between individuals - please research the morph and ask the seller about this specific animal before buying.