I was getting about half a dozen bot registrations a day so instead of using something that was dependent on a 3rd party, I thought of making my own cheap imitation and see how long it lasts.
I simply added my own .gif image to the registration page and used questions for human input based on words contained in that image. Not sure if using "avatar" as the image name contributes anything to the confusion for the registration bot or not.
This is what it looks like and fingers crossed it will work for some time:
Hope it might help others