According to the older field guides the Christmas Mts fell solidly within bull snake range and affinis were only found in the El Paso area. However, newer publications indicate that affinis ranges throughout all of Big Bend.

I think the Christmas Mountains are in an intergrade zone for bulls & sonoran gophers. Most of the animals I've seen from the bend tend towards affinis, but you can also find snakes there that have bull characteristics like a narrow rostral scale.

P

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