Well a "Red rat" snake is a Corn snake. Using the term "phase" is just a descriptive, it doesn't tell you anything about the actual species of snake (kind of like saying I'm a brunette phase). There are a number of rat snakes that could have a reddish phase, like Texas rats or Black rats for example. What colors are the snake (besides reddish)? What's the pattern like? What's it's place of origin? Is it an adult or juvenile? The pet shop should be able to give you the latin for any animal they carry as well as a common name.
If it's a Corn snake, they come in many colors and patterns at this point due to selective breeding. There's tons of care sheets out on the web for Corns as they're a very popular pet snake. If it's a Texas rat snake, you pretty much keep it like a Corn snake. However, if it's a Texan, be sure that it's captive bred, otherwise you're looking at vet bills from the get go for parasite treatment. The last wild caught Texas rat I had was a very defensive animal who bit and musked me at almost every handling.
Let us know what you find out, and do a google search on rat snakes to read up on them. I've been keeping rat snakes for about 16 years so if you run into questions about conflicting care sheets, I can try to answer them based on my experience.
__________________
Lora
|