The only natural predators a cactus has are all the people out there who buy them in tiny crafty pots and then let them die slowly over time (raises hand).
On another note, typing "Happy Cactus Dance" into Google gives you... a lot of MS Paint drawings. o_o
I know I kinda broke my own rule again, but that eyeball on Hazel was driving me NUTS so I nixed it here! Forgive me/you're welcome.