THE PIG PROJECT

The Pig

Wild pigs at Pinnacles are a cross between two strains of the same Eurasian species (Sus scrofa): European wild boar, and feral hogs (swine domesticated from European wild boar that have escaped captivity). Domestic hogs were released in California in 1769, resulting in a feral hog population. European wild boars were released at Hooper Bald, North Carolina in 1912, and from there introduced to California in 1925, for hunting purposes.  These two strains have found each other and interbred, creatingoffspring very well adapted to living wild in California.


Wild pigs were first observed in Pinnacles National Monument during the 1960’s, and by the 1980’s they were a common sight.  As the population of this exotic species grew it became increasingly obvious that they were negatively impacting park resources. They destroy native vegetation, compete with native wildlife for food, harbor diseases, increase erosion, and degrade water quality by rooting along banks and wallowing in creeks.  

Several examples demonstrate this negative impact:

  • Pigs often root along stream banks and on stream bottoms, prime California red-legged frog habitat. This rooting impacts the creek and its denizens, including red-legged frogs and their food sources. And their destruction of creek side vegetation makes it harder for frogs to hide from predators.
     
  • During the fall, acorns become the primary food source for pigs. One pig can consume between 13 and 16 pounds of acorns per day. Valley oaks have very specific requirements for acorn germination and survival and pigs appear to disrupt this cycle.
     
  • Pigs compete directly with black-tailed mule deer for acorns, so with increased numbers of pigs there are often fewer deer around.
     
  • Wild pigs are omnivorous and eat earthworms as well as other beneficial soil invertebrates and vertebrates when they root through the soil.
  • Several invasive plant species actively controlled in the park thrive in disturbed soils, the result of pig rooting. In one night, one pig can root up to 15 acres of land. These exotic plants get a better toehold because of pigs.
     
  • Wild pigs are reservoirs of diseases that can be transmitted to humans and other animals.  Pigs are particularly effective vectors because they roam over large areas and are often near creeks, so many of their diseases can be further carried by water. 

     

The Pig Fence:

The inspired vision of the Monument management team in the 1980’s was to realize that the proactive method to protect public lands from pig impacts was to create a fence perimeter, a solution that would minimize the park's need to be in the eradication business.  They accepted that the project as conceived would take many years.  The fence project was constructed by NPS and contractors with special project funds as they became available. 

The Pig Fence construction began in 1983, and when it was completed twenty years later in 2003 it enclosed 14,400 acres, much of it designated wilderness,.and was 24 miles long. A second section of Pig Fence was begun in February 2010, adding about 9 miles of fence and enclosing an additional 3250 acres. This section protects important springs, California red-legged frog habitat, and cultural resources in McCabe Canyon, the Pinnacles Campground, and the newly acquired Bottomlands area. 

Fence materials airlifted by helicopter to the remote areas made the completion of this second fence possible within a single year.  The fence construction and pig eradication were funded with ARRA (American Recovery Reinvestment Act) funds and NPS Natural Resource funds and implemented through competitive contracts.  In fiscal year 2010 PINN received annual operating funds on a permanent basis to maintain the fence and monitor pig activities. This project was a tour de force of multidivisional planning and coordination.

Eradication:

After the completion of the first pig fence in 2003, a total of 197 exotic pigs were removed from inside the pig fence. This took 2-1/2 years, and utilized a variety of techniques to accomplish this job as humanely as possible.  These involve trapping, using sturdy chain link fence enclosures, tracking by using remotely-triggered cameras and radio-collared pigs, as well as various ground hunting techniques.  Fieldwork for the eradication of the pigs inside the new section of the Pig Fence is now underway.  

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 The Pinnacles Pig Project Crew

Dan Ryan, Bryan Smith, and Ted Wilbur comprise the multidivisional Pinnacles Exotic
   Pig Management Team. They hike the entire pig fence on a monthly basis to find and
   repair breaches.  They work together to replace entire sections of fence as needed,
   keep the fence free of brush, monitor inside the fence for pig activity, and various other
   tasks to protect natural and cultural resources at Pinnacles from pig damage.  


Article written by Joseph Smith, Park Guide, Pinnacles National Monument