By Rachel Cramer
From a distance, the cattle grazing at the Land of the Swamp White Oak Preserve in southeastern Iowa look like they’re wearing cowbells. But instead of metal domes and clappers, these accessories are outfitted with global positioning system (GPS) chips.
Staff with The Nature Conservancy, the organization that owns and manages the 4,000-acre preserve, can track the locations of the collared cattle from a smartphone app. They can also draw and adjust virtual fences to graze cattle in certain areas with invasive weeds – and keep them out of ecologically-sensitive wetlands and floodplains.
When a collared cow moves toward a virtual fence, it hears a tone, which gets louder and eventually releases an electrical stimulus on the back of its neck.
“For the majority of these cattle, that's enough to turn them around. They don't stop grazing. They just keep going but change direction,” said Amy Crouch, who oversees sustainable grazing projects in Iowa through The Nature Conservancy.
Since 2023, she said staff have tested virtual fencing systems from two companies as part of a pilot project at the preserve. Calves and bulls don’t need collars since they follow the cows, Crouch added.
The virtual fencing reduces the need for physical posts and barbed wire – which can be difficult to maintain in areas with frequent flooding, like the preserve’s oak savanna floodplain.
“A big benefit [of virtual fencing] is not having to consistently rebuild fence,” Crouch said. “And that's not just a benefit for us. That's a benefit for private producers, too.”
Virtual fencing has evolved significantly since the 1980s when researchers tested shock collars on goats. But the technology is still relatively new and only recently became commercially available.
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