About 150 to 200 grizzlies live in Yellowstone. NPS/Jim Peaco Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Heeding legitimate signs is always important, but between May 1st and October 15 at Yellowstone National Park it will be particularly significant. These signs will help visitors avoid encounters with the friend-shaped but not-too-friendly member of the local fauna. “It is critical that all members of the public heed these signs,” the national park emphasized in a recent statement .  Yellowstone National Park is home to both grizzly bears ( Ursus arctos horribilis ) and black bears ( Ursus americanus ), with 150 to 200 grizzlies spending at least some time in the park. Grizzlies are a subspecies of the brown bear ( Ursus arctos ).…