Wow, what a great question!!!
This is so variable that all opinions you get here will have merit.
I’m not going to comment on the ethical issues of taking an animal from the wild. That would make an interesting thread on its own merit.
AND
It’s extremely hard to generalize on how easy it is to “man” a specific wild species or variant, because as soon as someone makes a blanket statement like “White Sided Snow Snakes are docile as soon as you pick them up”, this will surely be met by someone else saying, “White Sided Snow Snakes never become docile in captivity”, and both folks are probably right according to their life experiences.
In other words, there are few absolutes in nature.
AND
You need to be keenly aware of how your own state laws treat collecting of wild animals. Whether or not you agree with the law (another great topic of discussion), it is the law.
All that said, here are some opinions for “manning” a wild snake:
While snakes are not very demonstrative of intelligence, and much of how they act is from genetic memory, personalities can still be conditioned and developed, especially based upon types and frequency of predator encounters.
These animals sometimes can be deprogrammed of their defensive attitudes with patience handling them without emulation a predatory response.
Some suggestions:
1. If the animal defends itself vigorously, let it calm down and start feeding regularly, then handle it often in a supportive way, but don’t stress it too much. Be patient.
2. Scooping up the animal instead of grabbing it, as would be jaws or talons. You want to be perceived as a tree or a rock, and not as prey or predator.
3. Be prepared to get nailed a few times, so you don’t react violently when it happens and causes an escalated reaction from the animal.
4. I personally find “side loading” cages make feeding and handling a stressed wild caught animal a little more calming than “top Loading” cages (e.g. an aquarium). When you imagine the approach of mammal and avian predators, it’s almost always from overhead.
(Side note (no pun intended)– with very little handling of Rat Snakes in “side loading” cages, the animals quickly associate the door opening with food. I’ve gotten more bites of mistaken identity this way than with animals defending themselves.)
5. Be prepared to fail. As tex540 said, some are "spawn of satan".
If you just want any Emory’s, for example, you are better off buying captive bred (fewer parasites, less stress on wild populations, cheaper, etc.) If you want a locality specific animal (e.g. Alpine, TX Emory’s) collect responsibly and legally.
Wild snakes almost always have a parasite load. In the wild the animal has generally reached some sort of balance, equilibrium, but in captivity, we upset that equilibrium. Take a fecal sample to a vet, and treat accordingly.
Finally, if your screen name is "phiber_optikx", are you OC-12, OC-48, OC-192????
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Regards, Bill McGighan