conservation problem for hellbenders, a rapidly disappearing species that is a candidate for Endangered Species Act protection, throughout their range, especially wherever they exist in easily accessible streams on public lands. In Australia, rock-stacking was listed along with logging, mining and track construction as one of the threats to a newly discovered population of the Mountain skink, a poorly documented lizard species, in Wombat State Forest. Notable artists Adrian Gray, UK artist specialising in stone balancing sculptures and photography Andy Goldsworthy, artist for whom rock balancing is a minor subset of his "Collaborations with Nature" Bill Dan, American artist Michael Grab, balance artist and photographer, born Alberta, Canada See also Cairn Environmental art Inuksuk Rocking stone Rock on Top of Another Rock Sea stack Street art Trail ethics Utah monolith Yarn bombing References External links Stone-stacking as a looming threat to rock-dwelling biodiversity, a letter to the editor of Human–Wildlife Interactions Hobbies Installation art works Performance art Rock art Sculpture techniques