A Movable Sukkah?

(3) If one constructs his sukkah on top of a wagon or on top of a ship, it is valid, and one may ascend to it on the festival. If [one constructed it] on top of a tree or on the back of a camel, it is valid, but one may not ascend to it on the festival. If two [walls of the sukkah are formed] by a tree and one by human hands, or two by human hands and one by a tree, it is valid, but one may not ascend to it on the festival. If three [walls are formed] by human hands and one by a tree, it is valid, and one may ascend to it on the festival. This is the rule: any [sukkah] that can stand on its own even if one removed the tree, it is valid, and one may ascend to it on the festival.

If he used an animal as a wall of the Sukkah: R. Meir declares it invalid and R. Judah valid, for R. Meir used to say, Whatever contains the breath of life cannot be used as a wall for a Sukkah, nor a side-post for an alley nor boards around wells, nor a covering stone for a grave. In the name of R. Yose the Galilean they said, Nor may a get be written upon it. What is the reason of R. Meir? Abaye said: Lest it die. R. Zera said: Lest it escape. Concerning an elephant securely bound, all agree [that the Sukkah is valid], since even if it die, there is still ten [handbreadths height] in its carcass. Regarding what then do they dispute? Regarding an elephant which is not tied up.

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But is there not an open space between [the animal's legs]? [It refers to] where he filled it in with branches of palms and bay-tree. But might it not lie down? [It refers to] where it was tied with cords from above.