Moments in Time with Dave Van Cleve: Pigs – ¡Sus scrofa no es mi scrofa!
David Van Cleve has many ties to Anza-Borrego Desert State Park and Anza-Borrego Foundation. In the 1980s, he was an environmental scientist in the San Diego regional office, where he collaborated with park staff on many significant natural resource projects. In 1989, he was selected to serve as the superintendent of the state park. In 1994, his responsibilities were expanded to include management of six other state parks (Mt. San Jacinto, Cuyamaca Rancho, Palomar Mountain, Salton Sea, Picacho, and Indio Hills) in addition to Anza-Borrego. After retiring from state service, he worked for The Nature Conservancy as Ecoregional Director for the South Coast Ecoregion and added over 1,000 acres to the park. Each month, Dave will fill in some important issues in the history Anza-Borrego Desert State Park, which often dove-tail with the history of ABF. We are grateful for his wealth of knowledge of the Park and willingness to share with us!
Sus Scrofa (pigs) have had a minimal impact on Anza-Borrego Desert State Park. However, like all invasive species, efforts to control or eradicate it as a threat must continue indefinitely.
About 18 years ago, the natural and cultural resources of Anza-Borrego Desert State Park were threatened by illegal introductions of pigs into San Diego County. And, as with many invasive species, if the non-native species is not controlled or eliminated in the early stages of its introduction, it will create negative impacts that may never be controlled. The Anza-Borrego Foundation has supported the State Parks Department’s efforts to understand and manage the effects of these mammals on the park.
Many regions of California, particularly in northern and central California, are dealing with feral pigs in their natural and agricultural areas. Based on the number of pigs in the wild (perhaps 6 million nationwide), it is unlikely that some regions, Monterey and Santa Cruz Counties, for example, will ever get rid of wild pigs or their disruptive influences. Many counties have shifted to a situation where eradication is no longer a management option.
Pigs are not native to California. Historically, we believe that early seafaring explorers in the 16th and subsequent centuries kept pigs on board for food and released them at coastal locations in our state. Their hope was that pigs would reproduce and create a sustainable population of meat producers that these explorers could harvest when they (or successive explorers) could harvest. Pigs did reproduce, but they spread to habitats far from the coast.
Sus scrofa, or pigs (or swine, boars, razorbacks, or hogs), are tough on natural ecosystems. They are omnivorous, meaning they eat both plants and other animals. Once they are not in a domestic setting – in a sty on a farm, say – they develop thick coarse hair and tusks. Now, this change does not take place over many generations, as we would normally expect in a species’ evolution; it occurs in the same individual animal relatively rapidly. Weird.
They do not have sweat glands, so in warm weather they seek out sites with water to cool off – stream, muddy river banks, waterholes. Of course, these riparian ecosystems, especially in deserts, are home to dozens of native species, including endangered birds and toads, due to the rich biodiversity. One can imagine a feral (wild) pig finding a riparian corridor to be a rich environment indeed. Eggs, amphibians and reptiles, and small mammals succumb to the pigs’ carnivorous tastes. Plants, about 85% of pigs’ diets, are devoured as well.
Pigs find some food under the surface. Like a small bulldozer, pigs will root up the ground to find the floral species they prefer. After pigs go through, meadows can look like someone went crazy – tearing up the ground with a hoe.
Earlier, I mentioned the impacts of pigs on cultural resources. As we know, local tribes relied on riparian habitats for food, shelter, shade, and water. As pigs tear up the ground near rivers and streams, archaeological sites and features can be affected too.
So how does this impact Anza-Borrego Desert State Park? Mostly through good fortune, San Diego County has been free of feral pigs. About 18 years ago, some hunters bemoaned this fact and set out to release (illegally) several pig populations in the hope that they would become established in the backcountry and provide a source of recreation and food.
The release we know most about was near El Capitan Lake, an artificial reservoir just north of Interstate 8, 30 miles northeast of San Diego. The pigs did disperse, at first upstream the San Diego River, which runs from near Julian down through Mission Valley. The heaviest population density was near Cedar Falls, on the river east of Ramona.
Sows often have two litters a year, and a litter is usually composed of about 15 piglets. Math tells us that San Diego County was on the brink of a population explosion of feral pigs.
Quickly, reports of pigs from various parts of the county began coming in, along with complaints about the damage they were causing. Descanso, Palomar Mountain, Cuyamaca, Lake Henshaw, and Vista Irrigation District were being invaded. Anza-Borrego reported pigs in Upper Oriflamme Canyon.
Governmental agencies, local tribes, and conservation groups in San Diego County decided that a coordinated effort was needed because the pigs did not respect agency boundaries. The Forest Service, California Fish and Wildlife, San Diego County, California State Parks, and Vista Irrigation District were the key players. The local office of The Nature Conservancy funded experts to help guide the development of an effective, humane, and rapid strategy.
Within two years, this coordinated effort had nearly eliminated the threat from pigs. Although there are still likely a few feral pigs in San Diego County, the impacts on large tracts of conserved land have been reduced to nearly zero. Locally, seasonal environmental scientist Gary Reece live-trapped pigs in Cuyamaca and Palomar State Parks, as well as in Anza-Borrego.
In Anza-Borrego, the pigs never reached the park’s major wetlands – Carrizo Marsh, Sentenac Cienaga, Coyote Creek, or Borrego Palm Canyon. If they had, the park would likely be dealing with the problem in perpetuity.
Some people say that a bunch of hunters could easily transport pigs into the region and release them, presenting another major challenge to conservation efforts in the county. While that is true, we hope that the agencies and conservation groups now have a blueprint for addressing the issue.
Invasive species don’t rest — and neither does the work to protect Anza-Borrego. Become an Anza-Borrego Angel with a monthly gift and provide steady, reliable support that helps the Park respond quickly to emerging threats.