One of the mysteries yet to be solved. Some columnar cactus, like this organ pipe, exhibit an odd growth pattern called "cristate". Though considered unusual, a sharp eye can spot christate saguaros and organ pipes all across the sonoran desert.
This cactus might look strong, but in reality it was damaged by frost. The weight of the branches could not be supported by the damaged tissue, and the arms turned down. Now they continue to grow back towards the sky. Our imaginations often look at saguaro cactus as though they had their own personalities. This one is "making muscles".
By far the most hostile element in the sonoran desert, the cholla cactus will "jump" out and grab hold of anything too close. The cactus wren, arizona's state bird, uses this hostility to its advantage by building its nest within the braches for protection.