The ones we have seen live, I believe, are not poisonous, according to the internet. The species is called "Uysal" which is Turkish for docile.
There are around 45 species of snakes in Turkey, and of these around 10 are poisonous. The most common venomous snake is the black viper. Snakes are very rarely seen in tourist areas. It may also comfort you to know that between 1995 and 2004 (the latest period for which data is available), while 550 people visited clinics or hospitals due to snake bites, there were no deaths. Most snake bites were contracted in Marmara, Central Anatolia and Turkey’s Black Sea region.
However, a neighbour managed to kill the one pictured below after it had eaten one of his baby chickens. This one, he assured us, was indeed poisonous.
More warnings were given about a huge local Kangal dog called Marco. But after feeding him a few meals he began to roll over and demand that we rub his tummy. The Kangal can weigh up to 66 kilos but it is not as heavy as some other mastiffs and can actually reach speeds of up to 30mph. It is primarily a shepherd's dog but it does not herd sheep. While Marco is a gentle giant with us, he growls ominously at strangers so is the perfect guard dog.