06/01/2026
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In 1988, a hiker walked up to a ranger at Big Bend National Park and said he had seen black bears in the Chisos Mountains. The ranger told him he had probably seen javelinas. The hiker said he had taken photographs. He mailed a slide to the park. It landed on the desk of wildlife biologist Raymond Skiles.
It was a female black bear with cubs.
Skiles called it the eureka moment. Black bears had been gone from Big Bend and the rest of West Texas for roughly forty years. By the time the park was established in 1944, shooting, trapping, federal predator control, and settlement had wiped them out of the Chisos Mountains and every other range in the region. In 1901, biologist Vernon Bailey had described bears as common in the upper canyons of the Chisos, with fresh tracks of old and young frequently seen and an abundance of old sign and turned-over stones.
Forty-three years later, the park opened with no bears.
Scattered sightings trickled in over the following decades. In 1969 and again in 1978, female bears with cubs were seen in the Chisos. Individual animals wandered in from Mexico and wandered back. But nobody considered the bears resident. They were ghosts passing through a former range that had the habitat but not the population.
Then the photograph arrived.
Genetic testing by researcher Dave Onorato confirmed what the slide showed. Sometime during the 1980s, one or more bears, including at least one female, had crossed from the Sierra del Carmen in northern Mexico into the Chisos Mountains and stayed. The Sierra del Carmen is a rugged limestone range rising above the Rio Grande on the Mexican side of the border. Mexico listed the black bear as endangered in 1985 and closed the hunting season.
Texas followed in 1986. The bears that had survived in the remote Mexican sierras while their relatives were being exterminated north of the river now had legal protection on both sides of the border.
The crossing itself is the part that makes biologists pause.
Between the Sierra del Carmen and the Chisos Mountains lies open Chihuahuan Desert. Miles of it. Flat, exposed, waterless terrain with no tree cover and daytime temperatures that can exceed 110 degrees. A black bear crossing that gap is walking through country that offers no shade, no food, no water, and no hiding from anything that might be watching. The bear has to descend from the Sierra del Carmen, cross the desert, swim the Rio Grande, cross more desert on the American side, and climb into the Chisos. The NPS page describes the journey plainly.
She descended from the mountains, crossed miles of desert, swam across the Rio Grande, and traversed more desert to reach the forested slopes of the Chisos Mountains.
She did it because the mountains were there and something in her biology told her they were usable. A black bear does not read a map. It does not know the Chisos Mountains held bears before it was born. It follows terrain, water, and elevation. A sky island rising out of the desert floor with pine, oak, juniper, madrone, and seasonal water is visible from the Sierra del Carmen on a clear day. The bear saw a mountain and walked to it.
By early 2000, the park estimated at least thirty black bears were living permanently in the Chisos. Females were denning. Cubs were being born in the park. The natural recolonization of historic habitat was described by the NPS as one of the major events of the park's fifty-five-year history. Once a large animal is eliminated from its natural range, the NPS wrote, it is rare for it to return on its own. Often, only human intervention can bring back what humans caused to disappear.
The bears came back without human intervention. Nobody trucked them in. Nobody flew them by helicopter. Nobody built a captive herd and staged a release. The Sierra del Carmen held the source population. The Rio Grande was crossable. The desert between the mountains was survivable. The Chisos still had the food, the water, and the denning habitat that had supported bears before the settlers killed them. Every link in the chain held, and the bears walked through it.
Then the drought hit.
In the summer and fall of 2000, Big Bend experienced severe drought. The seasonal food sources that bears depend on, primarily acorns, piñon nuts, madrone berries, and sotol, failed across the Chisos. NPS researchers documented a remarkable migration of bears out of the park and back into Mexico. The animals that had spent a decade recolonizing their historic range reversed course and walked back across the desert to the Sierra del Carmen where the food was better. Skiles and Onorato watched the GPS data and the sighting reports and could not say whether the bears would return.
Some did. The population recovered after the drought broke, and by the 2010s bears were expanding beyond the park. Females with cubs were spotted north of Big Bend near the town of Alpine and in the Davis Mountains, the largest mountain range in Texas. The Chisos had become what Skiles always believed it could be, a natural steppingstone for the recolonization of the rest of West Texas.
Diana Doan-Crider, an adjunct professor at Texas A&M and executive director of a nonprofit called Animo Partnership in Natural Resources, spent years confirming the genetic link between the Big Bend bears and the Mexican source populations. Mexico has a thriving bear population, she said, thanks to its mountainous terrain and greater cultural acceptance of the animals. The recovery was possible because the bears had somewhere to come from, and that somewhere was Mexico.
The border wall debate added a layer that the original recolonization story did not have. A physical barrier along the Rio Grande through the Big Bend region would sever the corridor that the bears used to return. The female that crossed the desert and swam the river in the 1980s did it because there was nothing in her path except distance and heat. A concrete and steel wall in the river corridor would add a barrier that no black bear can climb, and the population that rebuilt itself through natural dispersal from Mexico would be cut off from the genetic source that made it possible.
As of the most recent surveys, roughly thirty to forty black bears occupy the Chisos Mountains and surrounding ranges. They are state-listed as threatened. They are still connected to Mexico by the same desert crossing their ancestors used. Whether that crossing stays open is not up to the bears. It is up to the people who decide what gets built along the river.
Source: National Park Service, Big Bend National Park / National Parks Conservation Association / Texas Parks and Wildlife Magazine / Earth Island Journal.
