First, science is like a our court system. Different judges will throw you in jail for different degrees of evidence. Its not the evidence, its about the judge and how evidence is presented. "If it don't fit, you must acquit".
So the easy part first, yes, many of us have caught wildcaught gravid females then have them double clutch. Which is leading soft evidence. Yes wild snakes can indeed multiclutch without captive intervention, other then food. That is, you can catch one in the spring and have it double clutch without another temperature manipulation.
Next, have I seen naturally occuring females multiclutch. Yes, and no. hahahahahahaha why there are judges. None that were captured and marked. But many that were observed, without intervention. It seems mucking with them, effects them the same way as mucking with captives. As in, not a good thing.
What this means is, for pure science(those who want to deny snakes do this) There is no exact DNA identification. But there are fingerprints. That is, the same color and pattern characteristics. That is, I have watched a female pyro become gravid several times in a year. But "could" it been several pyros? not in my mind, as no two pyros have the same markings. And more important, no two in the group I was watching. So this evidence is conclusive to me, but not to someone with no real experience. To some biologist, who has no idea what a pyro is, to the uneducated, all pyros look alike. I guess there could have been twins, it does happen(I must be really lucky, to have it happen over and over)
I often mention this to HKM while in the field. They(the teachers of biology) should not allow students in the field until they learn that no two snakes are alike. All have unique markings, builds, etc. They must learn to be able to recognize individuals. Unfortunately, some have a hard time with species, muchless individuals. So instead, they are trained to us, invasive techniques like radios, pittags, scale clipping, toe clipping, spools, etc. I am not saying they should not use these tools, but I am saying they need to have an understanding to the level of being able to recognize one from the other. If they cannot, it simply means, they are not looking hard enough. Or simply put, they are dumb as a stone. In any case, these are not the people you want taking data.
Also, and while weaker evidence, we see snakes of many species gravid over long periods of the year. We also see neonate blooms over long periods of the year.
Lets use gophersnakes. We can find them gravid in April, may, june, july, and august. Who is to say they only had one clutch. And why the heck wouldn't they have more then one clutch, they surely do in captivity, in spite of the narrow range of choices we give them. Even funnier is, in the later months, the gravid females get skinnier and skinner. Just like there captive relatives. Normally in good conditions, the first clutch does not take any toll. As in, you cannot even tell they laid. With natural supported snakes. Later in the year they start to look like captives, ahhahahahahahahahahaha lack of support.
One of the problems is, somehow, and I have no idea where this comes from. People think snakes cannot or have a hard time finding food. To me this is strange and odd. They always say, in captivity, they have all the food they want(which is normally bullbeans)
As a kid, I remember reading about a bull snake that was killed in a farmers field. It contained 97 mice. hahahahahahahahaha I never heard of any keeper feeding 97 mice in a single feeding. Also you see pics of wild snakes eating such large food items, they look like they are going to explode. You never see that in captivity. That one feeding weighs more then a normal captive years of food. In captivity they would indeed puke it up. Why? to narrow of temps to digest such a thing.
Also the vast majority of stable snakes I find, are super healthy, compared to their captive relatives. So whats that deal all about? Why would you think they perform less, when they look better? Why would they appear healthier and cannot find food? Why would they produce less and have wider choices? common sense says, people are dumb as a stone about snakes. Cheers