<p>It's early morning at Skyline Ridge Open Space Preserve, just south of Palo Alto, and park ranger Susannah Anderson-Minshall sets out for a routine inspection in her truck. She soon notices something that makes her slam on the brakes.</p>
<p>A creek that was filled with fresh water until yesterday now looks like a muddy bog. The ground all around is dug up, and ferns and plants lie trampled. She doesn't need to look at the huge, round, footprints in the mud to guess where the blame lies. The culprits are wild pigs, non-native, sharp-tusked, black bristly marauders who have been causing havoc across Northern California's landscape with increasing frequency.</p>
