There are about 150 mountain lion sightings in Big Bend National Park each year. In most cases, visitors glimpse the elusive predator from behind the wheel of a car. A lion sighting can be a thrilling and memorable experience.
Since the park opened in 1944, there have been only seven instances in which human beings have been attacked and injured by lions. The most recent attack took place in February 2012. A lion seized a 6-year-old boy while he was walking with his parents in the Chisos Basin, the most developed part of the park. The parents fought the lion off, but the boy was injured.
The lion was found and killed. Drought conditions at the time were extreme, and the lion was emaciated, and depleted by intestinal disease.
In the wake of the attack, park officials reached out to specialists at the Borderlands Research Institute in Alpine. And in 2014, the institute began a study in the park. It could help reduce the potential for dangerous encounters – and open a window into the behavior and demographics of the region's top predator.
Patricia Moody Harveson is leading the institute's research.
"When you think about all the lions that are there, it's amazing – it's such a tiny, small percentage of the time that something like this actually happens," she says. "But it's still something that needs to be addressed, and the park recognizes that, which is the reason for this study. It needed to be investigated."
Harveson and her team have used trained hounds and traps to catch lions. As of early March 2015, three lions had been trapped in the program, Harveson said. The lions are outfitted with radio collars, which allow them to be tracked on an almost hourly basis. The data sheds light on the lions' movements and diet.
Mountain lions can become specialists in hunting. One of the lions lingers in lower elevations and dines primarily on javelina. The institute has collared an older female lion. Her teeth are worn with age, and she sticks to rabbits and other small prey.
The institute has also installed cameras, in a 500-square-kilometer grid centered on the Chisos Mountains. The cameras provide glimpses of lions that haven't been trapped – as well as information on the density of prey animals.
The study could provide very specific data on the lion-human interface. Park officials believe one trail crosses multiple mountain-lion corridors, which could account for the high incidence of encounters there.
In a desert sea, the Chiso Mountains are an island of prime mountain lion habitat. Mule deer, javelina and other prey are plentiful. The Chisos are also the most heavily visited area of the park. A shared attraction to this isolated, highland environment may account for the rate of lion attacks.
In the mountains, a handful of springs provide the only perennial, natural sources of water. In dry years, effluent from the wastewater plant at the Basin lodge can be an attractive water source for wildlife. Park officials believe the effluent could be a reason for the lion encounters.
Harveson says the park could be home to as many as eight mountain lions.
Visitor safety is a priority for park officials. But the park service is also charged with preserving the mountain lion population, for the benefit of future generations. The BRI study could help the park balance these two aims.
"Because you want those animals there, those animals need to be there, mountain lions being the apex predator out here," she says. "They are extremely important in the healthy function of our ecosystems, so we want them in these environments, but we also have to respect that it's a very lethal predator, and so how we behave, and how we conduct ourselves in a situation like that, so that it allows both humans and lions to coexist – that's what's important."