The findings ran counter to the expectations of researchers, who thought the cougars would have moved eastward from California to Nevada, the Reno Gazette-Journal reported.
Because lions are hunted in Nevada but not in California, biologists thought more of the territorial predators would migrate east into habitat in Nevada made available when lions were killed by hunters.
"We predicted we would have more lions coming in from California. We were surprised the Sierra itself was a net importer," said Jon Beckmann of the Wildlife Conservation Society.
Researchers theorize the animals could be drawn to California because the Sierra offers lusher habitat with a greater selection of prey than Nevada's arid mountains.
"It may just be more attractive to move into the Sierra Nevada," said Alyson Andreasen, a University of Nevada, Reno, doctoral student and a lead researcher in the study. "It's just conjecture at this point, but that's what we think might be going on."
California is home to an estimated 4,000 to 6,000 cougars compared to Nevada's 3,000.
The study, jointly conducted by UNR, the Wildlife Conservation Society and the Nevada Department of Wildlife, used genetics to identify distinct populations of mountain lions in both states.
The findings were recently published in the online edition of Molecular Ecology.
Among the goals was to determine which areas animals move to at a greater rate than those that leave, and places from which animals disperse to other locations at a greater rate.
Lion population structures and history were determined by analyzing DNA from tissue samples taken from 739lions in both states.
Scientists were able to trace lion movements over multiple generations, saying such information is particularly useful when it comes to managing cougar populations.