I could actually buy that theory about bramble, as I have seen animals trapped that, had they not been rescued, would surely have died and rotted to nourish the bramble. Gruesome, but undeniably effective.
Down in Jackson County, Oregon, there's an area above the Rogue River that is home to pitcher plants. It's obnoxious country, sere and rawly rugged, so I didn't bother them, as is prescribed anyway.