Mountain lions can be hunted in Nevada but not in California, and wildlife researchers had thought more of the territorial predators would migrate east into Nevada to take advantage of big cat habitat made available when lions were killed by hunters.
"We predicted we would have more lions coming in from California. We were surprised the Sierra [mountain range] itself was a net importer," Jon Beckmann of the Wildlife Conservation Society said.
California may be attracting the mountain lions because the Sierra region offers lusher habitat with a greater selection of prey than Nevada's arid mountains, researchers said.
"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 with Nevada's 3,000, the San Jose Mercury News reported.