"I think we've steadily trended upward in terms of hog and vehicle collisions over the last 10 years," Higginbotham said. "There's a much higher incidence now than there was five years ago. And five years ago, it was greatly increased over the five years before."

The growing trend is strictly a matter of statistical odds as, from all indications, the feral hog population is increasing, he said.

Typically, feral hog sows will have a litter a year, and the litter size averages five. Though they can have litters of their own earlier, the female piglets will usually have their first when they are about 13 months old, Higginbotham said.

"Feral hogs are the most prolific large mammal on the face of the Earth," he said. "There's no question about that."

Higginbotham was recently invited to give a presentation at the eighth annual International Symposium on Wild Boar in the United Kingdom. He learned from his international colleagues that as bad as the problem is in Texas, the situation is worse in some other countries.

"France and Germany each estimate that the annual collision rate is 2 percent to 2.5 percent of the population," Higginbotham said. "Therefore, they estimate 20,000 to 25,000 collisions per million hogs."

In Sweden, wild pig collisions have quadrupled since 2005, he said, and research indicates that rate of incidents is tied to specific levels of vehicular traffic. Light traffic means fewer accidents, of course, but with higher levels of traffic, numbers of collisions reduced.

"The peak collision rate occurred when traffic was at 86 cars per hour," he said. "The conjecture was that higher noise levels associated with more car traffic made the hogs more wary. Less traffic and the numbers decreased."