Woodpeckers usually excavate a whole new hole each year, 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 over the dwellers in a gap. https://ramseyx604rzh7.azuria-wiki.com/user