Hi Ilias,
Very nice observation, I wish I could observe such a scene one day. What about a "dry bite" from an unexperienced juvenile viper? I recall a friend of mine being bitten by Bitis arietans (he panicked/ fainted as he knew what just happened and the consequences)but as a matter of a fact, no venom was injected eventhough teeth were deep in his arm. It did not even get reddish around the bite site. So I guess vipers have somehow the control on the venom they inject which maybe would require some "training".
I just hope this little guy learn quickly how to kill and feed ;-)
Cheers
Johann
PS: The same thing happened to this T lepidus and M monspessulanus. It this case, the venom is for sure not as potent to kill a large T lepidus so it was difficult to draw any conclusion.
Click on the link here below
http://picasaweb.google.com/Johann.Mols/EuropeanSnakes#5287479758643389714 

Hello Johann
I believe it is quite impossible for the viper to give a dry bite when attacking on prey. This could happen easily on a defense bite as a warning, like in your friend's case but I don't think it could happen in a case of attacking to kill and feed. I don't know how long was the viper holding the lizard but it seemed to me it was quite long before I saw the scene. The lizard was not fighting to escape as the vipers was holding it, so maybe some time had passed. After the viper released it it was shocked because I could touch it for a while without it trying to escape.

I don't know, it looks like a mystery to me... :-) 

It’s a strange one Ilias, you would expect a viper to strike, envenomate then release, only for it to wait for it’s pray to succumb to the venom.
When you saw L.stellio in its mouth it should have been close to death!
Maybe young vipers teeth are not big enough or strong enough to penetrate the skin of L.stellio.

With the Montpelier its different they must have a chewing action for the rear fangs to come into play to envenomate, the venom is week and i wouldn’t be surprised if a
T. lepidus could struggle free only to die some time later, thats if it was envenomated!


Tony
 

Maybe the little viper used his venom earlier that day and didn't have any left? 

Vipers never empty their poison glands, so they can't practically 'run out'. I'd guess it just an unexperienced juvenile, combined with a though-skinned prey item... 

I think, reptiles have some ammount of immunity to vipers venom.
Two examples, I have observed in the wild.
1) I found a large (70 cm) ammodytes some kilometres south of Zadar, Croatia - and this viper had another snake in it. When I craped it to make a few pictures, it regorged an ammodytes of nearly same size, still alive. I took the prey to the car, washed it and put it into a snakebag. She was still alive the next day, showing no effects of venoming or gorging.
2) Another ammodytes tried to feed on a huge trilineata near Parga, Greece. I was observing this spectacle for about 20 minutes (sorry, I had no camera with me): After that time the viper released the lizard - it was much to lage for her, she wasnt able to come over the complete head - and the lizard run away without showing any effects. I saw the trili about one hour later on my way back (with some blood on its head, so it must have been this specimen), showing complete normal behaviour.
So my opinion is, vipers must inject a lot of venom to kill one of her relatives.
A contrary example: A short time captive kept young Telescopus fallax on Krk island was fed with full grown Podarcis siculus. One lizard was dead within 5 to 6 minutes after chewed by the ophistoglyphe.
Mario 

I think your right Mario, Immunity amongst snakes has been well documented eg. The King cobra in Asia and king snakes in the USA amongst others.
Mammals too like the mongoose, meerkat’s and I’m sure I read a report that Hedgehogs were immune to V.berus bites, So it wouldn’t surprise me if some lizards have immunity to venom.
it’s an interesting subject!
 

I'm having my breakfast now and then I'm off to that place again for 1-2 hours. That's interesting staff! :-) 

European vipers sometimes dont strike and leave the prey till its dead, but hold it in their mouth with injected teeth until its dead. Especially they do it with small mammals and lizards, and if they are realy hungry (first food after hibernation?).
But ammodytes may kill another ammodytes sometimes within seconds.
Examples from my captive kept vipers:
Not dangerous: After biting into the head, the head of the bitten ammo got swollen very strong within 5 minutes. One eye was completely filled with blood. The swelling have gone away within 12 hours, but you could watch the blood in the eye going down for the next 5 days. The viper was feeding some hours later and had no long time effects of the bite.
A sad example: One ammo bite another into the head and must have hit the brain through the fontanella. The bitten viper turned around her own axle about 10 times and was dead about 30 seconds after the bite.
So my opinion is: If no vitally important organs have been hitten, they will recover in most circumstances.
Mario 

no vipers today... :-(