Thank you Mike for your reply and the interesting link. When we were planning our move to Ibiza we were interested to read that Ibiza was free of snakes. Coming from Australia we were more than happy about that. But now it seems snakes are inadvertently being introduced in the crowns of Palm trees and Olive trees which are imported from North Africa and mainland Spain. Rotten things are a threat to the distinctive Ibiza lizard and other native wild life. Hopefully the large number of feral cats here will prevent them becoming too much of a problem.