It is really that they are adapted to eat “thorny plants”, and new world cacti are superficially similar enough that they have no problem. Just like South/Central American Cane Toads weren’t adapted to eat a measurable chunk of Austrailian biodiversity, they still make a good go of it.
Man, I was ready to go full on plant biologist on the post for the following statement
“Their mouths are adapted to eat whole pieces of prickly pear cactus”
But then blurb from TFA covered it better than I ever could. Good jorb.
