I'm not too sure why you'd select Western Diamondbacks to begin with as a breeding program effort, but they are one of my favorites...
The hardest part of getting rattlesnakes, western diamondbacks that is, to breed is ensuring you have at least one male and one female.... Depending on growth rate and a few other husbandry concerns... access to heat, health etc... Westerns can begin breeding at about 18 months to 2 years of age. I recently sold a captive bred female het for amelanism that was gravid at age two... she was 36"-40" in length and about as big around as a 12 oz. soda can....
I keep the snakes separated in individual cages and introduce the female into the male's enclosure at varying times through the spring, summer and fall... just to allow them time to get to know one another, sort of... in the fall, I stop feeding and gradually cool cages to 55 degrees or so after the snakes have had time to clean out their digestive tract, and keep them in low light, cool conditions for about 12 weeks. Check them daily and make sure they always have access to clean drinking water. When the brumation period is over, I warm them slowly to "normal" temperatures and begin offering food. After they have shed, I introduce pairs and see what happens.... my atrox breed in the fall mainly, so the spring breeding, if it occurs, isn't the time when fertilization takes place, or at least I don't think it is.... females, gravid females, should be offered smaller meals than normal to get them to eat something if they'll take anything at all... and they should have access to a basking spot of at least 90 degrees. Notice I didn't say to keep them at 90.... just offer a nice place for them to heat those babies up if desired....
That's about all... C. atrox are about as hard to breed as rats.
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