any accidental wild Tham population in Europe

[Stefan-A]

What would be the minimum number to form a sustainable population?

One gravid female with a bit of luck.

What sort of range do individual garters cover within a breeding population?

Typically, they move a few hundred meters to a few kilometers during a season.

I suspect that the number required within a relatively small area would be quite high.

The density would matter, yes. No idea how many per hectare would be sufficient.

I expect there are odd escapees that survive for years in the wild, but not a population.

I'd have to agree. It also takes more than survival to actually establish a population and climate is the best predictor.

[Thamnophis]

I only "know" the Swedish population, but have never seen prove of any kind.
But I am convinced that when a number of specimen of one of the northern Thamnophis species escaped in parts of the Netherlands, they would have a chance to be succesfull.

[PINJOHN]

There we go, in the UK:

Section 14(1) of the Wildlife & Countryside Act 1981 makes it an offence for any person to release or allow to escape into the wild any animal which is of a kind which is not ordinarily resident in and is not a regular visitor to Great Britain in a wild state.

So in principle you could be prosecuted if your snakes escape by accident because you hadn't taken the measures necessary to prevent them from escaping. I'm not sure how heavily the law is enforced, one snake you'd probably get away with, but freeing 20 babies may be pushing your luck.

Hey Chris now you have got me paranoid about my admission in the Warren Buffett thread

[Serpico]

I'm not Europe, but would releasing to the wild be legal? From what I've heard here on the forum wild populations in most areas are strictly protected.

I have never heard of garters in Italy, wild ones, of course; and as it is said here, releasing them would be illegal, as to collect wild reptiles born here.

All wild indigenous reptiles, and anphibians are protected, sadly, here.
And I say "sadly" because no one prosecutes the ignorants, the farmers, the hunters who mistake a a coluber for a viper and kills it..and when I point out that a thousand or more mice will thank the senseless act, they just shrug.

While, if I capture a wild "biacco" (Hierophis viridiflavus), great mice and rats controller, and I am caught, it is a fine from 250 to 3000 euro, and possibly, some months in jail.

At the same time, one roman park's little lake is full of those turtles commonly found one inch small in pet shops. In the said lake, those turtles, left unopposed, have reached the size of more than 10 inches...prey on everything else, so only huge fish survive, with them, and the whole population of small fish, frogs and toads have been wiped out.

[Stefan-A]

At the same time, one roman park's little lake is full of those turtles commonly found one inch small in pet shops. In the said lake, those turtles, left unopposed, have reached the size of more than 10 inches...prey on everything else, so only huge fish survive, with them, and the whole population of small fish, frogs and toads have been wiped out.

One weekend with a .17 rifle and a few boxes of ammo, and that pond would be turtle-free.

[Bart]

I believe you're talking about red-eared turtle. It's an invasive species and releasing it in EU (in Poland for sure) is a crime. In Poland there were several reports of that turtle (that fled from captivity or were released by humans) but I doubt it can reproduce in our climate (nevertheless, it can find a proper places where specific microclimate occurs I guess; probably in southern Europe it can establish real populations). But it probably can survive many years (especially winter) and decimate local populations of semi-aquatic turtles like European pond turtle (Emys orbicularis) if given a chance.

As for Thamnophis spp. in Europe, as Stefan once said, it probably can't survive, because almost all fish in Europe contain thiaminase. Maybe they >could< live solely on frogs but as we all know, Thamnophis spp. WILL hunt fish if there's a pond or the river around and snakes probably would seek actively such places or, for instance, find themselves there as a result of following amphibians (not to mention that most amphibians live close to water). Moreover, those snakes would probably hunt down european toads. They aren't immune to their venom though (unlike Natrix natrix) and would probably succumb to it.

In conclusion, the climate looks appropriate, but there's a food barrier that prevents Thamnophis spp. runaways to thrive, not to mention establishing a population in Europe. I may be horribly wrong though.

[Stefan-A]

In conclusion, the climate looks appropriate, but there's a food barrier that prevents Thamnophis spp. runaways to thrive, not to mention establishing a population in Europe.

I hope that's the case anyway.

[Serpico]

One weekend with a .17 rifle and a few boxes of ammo, and that pond would be turtle-free.

Lol!! I wish I could do that, maybe with salt loaded shells; but not to turtles, rather to whom freed them there! It was a beautiful little lake, now is a stinking swamp...
Seriously, they are protected as they were considered autoctone. And in Italy every wild reptile is protected.

[zooplan]

There is an old field herp study naming Thamnophis sirtalis to be neozoen in Germany:

DORSCH, A., MAUER, H., TREPTE, M. 1993: Die Amphibien und Reptilien des Main-Taunus-Kreises. Arten,
Lebensräume, Gefährdung, Schutz. Ergebnisse aus der herpetologischen Kartierung im Main-
Taunus-Kreis (1989-1993). Schutzgemeinschaft Deutscher Wald, Stadtverband Hofheim am
Taunus e.V. 91 S. + Anhang.

I had no glance at the paper and can say nothing about its´content, sorry!
Last year an adult female Plains Garter Snake was found and released at the other border of the river Rhein
only few kilometers from my home.
BTW: All my T.radix are save !!!

[PINJOHN]

Moreover, those snakes would probably hunt down european toads. They aren't immune to their venom though (unlike Natrix natrix) and would probably succumb to it.

In conclusion, the climate looks appropriate, but there's a food barrier that prevents Thamnophis spp. runaways to thrive, not to mention establishing a population in Europe. I may be horribly wrong though.

establishing a population in Europe. I may be horribly wrong though. [/QUOTE]
I not sure about your European toad theory i would bet there is little, possibly no, difference in American/European toad toxins i remember one of Shannons threads where she reported huge eastern,s both size and population, that were apparently living on toads which were present in almost plague proportions