Keeping animals in cage for circus is not as sin as caged a bird who deserve for a freedom to fly. In circus the commander in charge that train beast to become circus pet animals use a device form of holy Hindus wood -tree / rukh @ katha that named "VARUNA" ` a typcal white wood that makes 1000 firece venom snake abode and tame to the wood stick that behold by the circus commander...in that case of the tube pic above mah personaly say its voids...