Staff found the boa constrictor – which in the wild kills its prey by squeezing the life out of it – in a polystyrene box outside the front gate of the RSPCA centre in Surrey.
This week the South Godstone Animal Centre has also taken in a harmless corn snake and three little gecko lizards, which live on insects.
Supervisor Clare Hyre said: “We had no idea what was inside the box. As we started to open it, this long tail shot out. I got quite a fright. In the 12 years I have worked here I have never seen anything like it. It was lucky that we found this snake when we did – the box could easily have been missed and she was lucky to be alive.”