Tucson hiker Joan Chen carries a camera whenever she hits the trail — and that preparedness paid off when a chance encounter with two roaming bighorn sheep resulted in a series of dramatic, close-range photos of the often elusive critters.

“I was very surprised to see two of them standing there — looking right at me,” said Chen, whose bighorn encounter came during a sunset-hour hike Tuesday on the Pontatoc Ridge Trail in the Catalina Mountains north of Tucson.

“I was ready,” she said. “I have my camera with me all the time.”

The Pontatoc Ridge Trail is southeast of the Pusch Ridge area, where bighorns from elsewhere in Arizona have been released in recent years as part of an effort to rebuild a herd in the Catalinas.

Had the sheep photographed by Chen made their way to Pontatoc Ridge from the Pusch Ridge area — or might they be a pair of wandering bighorns from a herd in Ironwood Forest National Monument northwest of Tucson? Those two bighorns have been spotted in recent months at Saguaro National Park and other sites in the Tucson Mountains.

One factor that might have helped answer the question was that the bighorns in Chen’s photos aren’t wearing GPS collars — devices that were fitted on most of the bighorns released on Pusch Ridge.

But Mark Hart, spokesman for the Arizona Game and Fish Department, said the matter is complicated by the fact that GPS collars on many of the released sheep have fallen off the animals after batteries on the collars expired.

The bighorns in the photos “could be animals that have had their collars drop off,” Hart said.

He said there is only a “remote possibility” that the animals are the two roaming bighorns from the Ironwood Forest herd.

“The last sighting of those animals that we know of was at the extreme northern end of the Tucson Mountains, suggesting that they might have been moving back toward Ironwood,” Hart said.

“It might have been difficult for them to get across Oracle Road (Arizona 77),” which would have been necessary to reach the Catalina Mountains, he said. “There is a wildlife-crossing bridge over the road. But we have multiple cameras up there, so we would have known if they crossed the bridge.”

Contact reporter Doug Kreutz at dkreutz@tucson.com or at 573-4192. On Twitter: @DouglasKreutz