Brett Wiedmann knows that 15 Oregon bighorn sheep were released in North Dakota's Badlands Sunday, but what's been frustrating him since is what he doesn't know: How are they faring?

The state Game and Fish Department's bighorn sheep biologist has been expecting to hop aboard a plane since Monday afternoon to check his charges, but fog keeps grounding him.

"I'm not happy," he said Wednesday while again hoping the fog would burn off and allow him to conduct his aerial survey. "An animal could be 50 miles away, or they all could be right there. I just don't know."

All 15 bighorns - three rams and 12 ewes - were fitted with radio collars between being captured in Oregon and transported to North Dakota, and Wiedmann said flying was the best way to check on them without disturbing them.

"You can hear them up to 20 miles away," he said of the radio collars.

What Wiedmann does know is that Sunday's releases went very well. Five sheep were set loose to augment the last Oregon transplants. The other 10 were released closer to the North Unit of Theodore Roosevelt National Park.

Wiedmann rated the health of 14 sheep as 10s on a scale of 1 to 10.

But one older ewe worried him. He rated her health as a 5. Veterinarians on site checked her out, Wiedmann said, but he described her as "a little stiff" by the time she was released.

"It's a risk. When you capture wild animals and put them in horse trailers, they go into lot of stress," he said. The typical mortality rate on transplants is 3 percent, he added.

The three rams are youngsters, which Wiedmann wanted. Young rams generally stay close to the ewes for the first three years of their lives, he explained. Two rams are yearlings, and the third is a lamb.

Four of the females are yearlings, two are 2-year-olds, three are 6-year-olds, two are 7-year-olds and one is 8. Wiedmann characterized the older ewes as "about middle-aged as far as sheep society goes."

The ewe Wiedmann is worried about is one of the 7-year-olds.

All of the ewes are pregnant, including the four yearlings. Ewes typically breed when they are 21/2, Wiedmann explained.

"It's phenomenal," he said.

Bighorns' lambing season usually runs from late April to early May, but Wiedmann will leave the herd undisturbed until July when he will do a lamb count.

For now, he continues to sit and wait for the phone call that tells him it's safe to fly.

"We had perfect weather in Oregon," he said, "then the fog rolls in in North Dakota."

(Reach reporter Richard Hinton at 250-8256 or outdoors@bismarcktribune.net.)