Feral Hogs and Water Sources in Big Bend National Park

Woolman, Mike

The basic goals of the field work carried out was to: 1) get a better picture of hog distribution within the park, 2) determine the amount of hogs present within the park, 3) document hog damage, and 4) survey water sources throughout the park in an effort to get pre-impact data and prioritize water source conservation. The European wild boar (Sus scrofa), which was introduced to South Texas in the 1930’s, has expanded its range throughout Texas. A sizeable population now exists in the Davis Mountains north of Big Bend National Park, and the range of these hogs has extended to desert habitats within Big Bend National Park and neighboring ranches. National Park guidelines call for the protection of native ecosystems and native species within the park. The expanding range of feral hogs will negatively affect these systems and biota through the detrimental habits of their ecology. One fear is that the feral hogs currently in Big Bend will expand their range into the Chisos Mountains. This is thought to be an undesirable event because of the potential of the wild boar to compete with the diet of the only U.S. population of breeding Mexican Black Bears, which is found in the Chisos Mountains. When available, acorns can provide as much as 50 to 48 percent of the diet in wild boars in the fall and winter (Springer 1977). If the population of wild boars reached a sizeable number in the Chisos, there may be serious competition for the acorn mast between many wildlife species. Another fear is that feral hogs will expand their range along the Rio Grande in Big Bend National Park and negatively affect this riparian habitat. Currently feral hogs exist east of Big Bend along the river near Del Rio, and west of Big Bend along the river in Big Bend State Park (information is from informal conversations with people familiar with the area). Although Santa Elena Canyon and Boquillas Canyon represent significant geographical bottlenecks for inhibiting the spread of hogs along the river, it is only a matter of time before they begin to filter through and expand their range. Besides river habitat, it is feared that the feral hogs will damage the natural water sources of Big Bend through wallowing and rooting activities. Currently there are 324 known natural water sources within the park, including springs and tinajas. Given the arid nature of the Big Bend environment, these water sources would most likely be essential for hogs to survive and spread throughout the park.