Woodpeckers commonly excavate a new gap annually, leaving the old gap for other cavity-nesting birds. Cactus spines deter animals from climbing the cactus. Seemingly, even so, they don’t deter snakes. I’ve found pics of a gopher snake climbing a saguaro to prey on the dwellers inside of a hole. Saguaros https://spencerhatjw.frewwebs.com/35476622/top-saguaro-for-sale-secrets