One year could've been a statistical fluke. Two years defies happenstance and begs for logical explanation.

"Yeah, two years of this. You'd think there has to be some reason for it," says Johnson, who ranches with his dad, Keith; uncle, Wayne; and brother, Jeremy.

The Johnson ranch has seen its share of twins before, but the past two springs have been extraordinary.

Last year, 58 of the 480, or 12 percent, of cows on the Johnson ranch gave birth to calves.

This year, 50 of the 350, or 14 percent, of the cows giving birth so far have had twins. Chris Johnson is confident that more twins will be born this spring.

Both those rates are exceptionally high. Johnson says he was told by a veterinarian that about 3 percent of beef cows typically have twins.

But the rate of twin births can be influenced by a number of factors, vets say.

For instance, cows with good body condition are more likely to have twins. And the calves that ranchers keep as heifers to replace older cows sometimes have greater odds of giving birth to twins, a trait of which producers may be unaware.

Johnson notes that the family ranch keeps back calves as replacement heifers, although he's uncertain if that's the reason for the high percentage of twin births.

The ranch hasn't changed the way it does anything, so whatever factor or factors that contributed to all the twins last year apparently affected this year's calf crop, too, he says.

"We just don't know what's causing it. But after two years, we think there's got to be a reason," he says.

Twins mean extra hassle

Twin calves are more curse than blessing to ranchers.

Sure, the second calf potentially provides another animal to sell. But twin births also bring problems, including more dead calves and more work for the rancher.

Both twins of a half-dozen sets of calves this spring were stillborn, and one twin in the many remaining sets also died, Johnson says.

Cows with two surviving twins are seldom able to provide both with sufficient milk, at least not for long. So one of the twins typically is fed by bottle or switched to a cow without a calf of her own.

"There's no bottle-feeding yet, but we know that will come," Johnson says.

Cows that give birth to twins go through more stress than cows with single calves, which often makes rebreeding a cow with twins more difficult. That's yet another reason why Johnson prefers a single, healthy calf to twins.

A late-spring snowstorm dumped roughly 2 feet of snow on the Johnson ranch, creating "a muddy mess" during calving, Johnson says.

Despite the snowstorm and the spate of twins, calving has gone reasonably well this spring on the Johnson ranch. The calves generally are avoiding the physical ailments that wet conditions sometimes bring.

Johnson won't be surprised if he sees double during 2012 calving, too.

"I've prepared myself for a lot of twins next spring," he says.