Monitors are destructive and blackthroats are ground dwellers. They LIKE to dig in stuff and love to destroy stuff. Mine broke 8 heat lamps in their currant cage before I got it caged off so they couldn't knock it around. And they STILL managed to knock it hard enough with a tail whip to break another one. They regularly dig up the whole substrate, or turn over the hide box. It's just what they do. They're weirdos.