You’re watching some bighorn sheep, but are they Rocky Mountain bighorns or their cousins, desert bighorn?

One easy way to tell, although it’s completely unofficial, is which side of Interstate 70 you’re on. With a few exceptions, it’s generally accepted that Rocky Mountain bighorn sheep are found on the north side of the highway while desert bighorn inhabit the south side.

Terrestrial biologist Stephanie Duckett of the Colorado Division of Wildlife offers a few more-scientific ways to ID sheep.

“Desert bighorns, because of the warmer climate they inhabit, are smaller than Rocky Mountain bighorn sheep,” Duckett said. “Also, desert bighorns tend to be more gray while Rocky Mountain sheep can be chocolate brown.”

Here are a few other facts: The horns on a bighorn ram may reach 10 percent of the animals total weight. Horns weighing 30 pounds are common.

Horns on a desert bighorn curl out farther from the head while those on a Rocky Mountain bighorn curl close to the head.

Rocky Mountain bighorn rams can reach 500 pounds. The ewes may weigh 200 pounds.

It’s thought that 200 years ago, bighorn sheep might have numbered more than 2 million across their West-wide range, but hunting, competition from domestic sheep and diseases knocked back the herds to where only several thousand were found by 1900.

Today, bighorn sheep have staged a comeback thanks to a concerted, long-term effort to restore the herds.

It’s estimated there are approximately 325 desert bighorn in Colorado and roughly 7,000 Rocky Mountain bighorn sheep.

Habitat, disease and predation by mountain lions are the main limiting factors in building desert bighorn sheep herds, according to the Division of Wildlife sheep management plan.

Email DAVE BUCHANAN