NORFOLK, Neb. (AP) — The Nebraska Game and Parks Commission says a slowly-growing mountain lion population is suspected of killing some of the state’s also-thin bighorn sheep herds.

Mountain lions are strongly suspected of having killed five bighorns between June and March, and nine since 2015, in western Nebraska.

Sam Wilson, the commission’s carnivore program manager, told commissioners Friday at a Norfolk meeting that he’s “very concerned about this.”

Nebraska started reintroducing bighorn sheep in 1981. Most of the five herds suffer setbacks from disease and poor lamb survival.

Mountain lions are native to Nebraska, but were eliminated by the end of the 1800s. Cougars from neighboring states started returning in the 1990s, and there are small breeding populations at three western Nebraska sites.