Male prairie dogs are normally fast and tough. They can easily avoid predators. But that's when they're not in love.

Scientists who spent years studying a colony of about 100 prairie dogs in Utah discovered that when it's time to court females, males become too distracted to pay attention to anything else—including predators.

The mating season for Utah prairie dogs lasts only 17 days, and each female is ready to breed for only 5 hours once a year. This means that males don't have much time to mate, so they tend to focus all their attention on breeding.

The researchers watched prairie dogs from sunup to sundown for several months each year for 10 years. When they arrived in 2005, they saw something new. A fox was hanging around trying to catch the prairie dogs.

Foxes are normally very shy around people. So, it's unusual to catch sight of a fox hunting. This particular fox, however, must have gotten used to people, and the researchers had a front-row seat as it went after prairie dogs. The researchers also spied at least one goshawk—a bird that swoops out of the sky to snag prey—in the hunt.

In 4 months, the researchers observed these predators kill 26 prairie dogs. Many of the victims were adult males who were apparently too busy paying special attention to the females to avoid capture.

Predators often prey on the old and weak, the scientists say. But the prairie-dog study shows that, at certain times of the year, healthy adult males can be at risk, too.—C. Gramling