<p>SAGUARO NATIONAL PARK, Ariz. — When Steve Bolyard checked out a report of black paint on some of the park’s majestic saguaros — cactuses whose towering bodies and upraised arms are as emblematic of the American West as red-rock buttes and skittering tumbleweeds — he did not expect to see ganglike calligraphy covering more of them than he could easily count.</p>