Spotting

Thanks for the great comment Dangermouse :D I am also looking at the Arctiidae family.

I'd take a guess at a caterpillar from the moth family Arctiidae. Looks similar to a giant leopard moth caterpillar (http://en.wikipedia.org/wiki/Hypercompe_...). But I could be wrong!

A fantastic looking fellar! Look at him! And the thorns he's standing on at well! A great spotting.