I often see so-called snake experts hold venomous snakes behind the head. While this was once considered a reliable, safe technique, it has fallen out of favor in recent years. It is just too dangerous, and these photos demonstrate why.
I caught this big eastern kingsnake (nonvenomous) one day in North Carolina. It was in shed, but I wanted to hold it up to show just how large it was. The snake was none too happy with being molested in this manner, and so I had to hold it behind the head. As I did this, the snake twisted in my grip and managed to get one side of both jaws around my thumb. I figured that as soon as I let go he would let go. Wrong. Once I let go, he was allowed to wrap his jaws around my thumb and give me his full fury. Knowing that his recurved teeth would only make things worse, I didn't try to pull him off, but set him on the ground and let go of his body. Again, I thought he would let go when he realized he was free. Wrong again. Instead, he only bit down harder (I swear I felt teeth scratch bone) and started to pull me around. After about 10 seconds, I was done waiting for him to let go and reached into my pocket for an ID card with which to pry his mouth open. At that time, he finally let go and made his way into the forest. After I washed my hand it was fine, but the story would have been very different if this had been a copperhead or rattlesnake, both of which are perfectly capable of twisting and biting in the exact same way.
The moral of the story is; DON'T HOLD VENOMOUS SNAKES BY THE HEAD. In fact, its better if you don't even touch them at all! And, if you try to hold a nonvenomous snake in this manner, as I did, be ready for some pain.
Lampropeltis getula (eastern kingsnake), Mecklenburg county, North Carolina
I've been messing with snakes for years. Holding a snake by the head is safely done if done correctly. Holding venomous snakes at all is a big no no to those that don't know what they're doing. I've handled hundreds and take doing so VERY seriously. Holding a snake by the tail supporting its bodyweight although seen on animal planet, et al. can injure heavier snake (if anyone cares). If you must hold a snake by the tail, use a hook, stick, golf club, ect to support the front part of the snake. Doing so often will even relax the snake making it less dangerous.
Been hunting vipers for a while.
As you said, better in fact hold by the tail (extremity), the snake can't pull his head back up to your hand...but can slightly swing. Anyway it's much more safe for people who are not used to hold snakes.
However...holding by the head is actually very safe when it's well done (that's why they are so called experts). The thing is : you have a specific finger placement right under the jaw and you must hold the snake *very* tight untill the jaws start to open (sorry for my approx. english)...but still...at the end...better not try to hold snakes ;-)