Virtual fencing

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Sep 4th 2008
From The Economist print edition

Electronics: A new way of corralling cattle, using satellite-tracking and warning signals rather than fences, is being tested in New Mexico
Illustration by Belle MellorBUILDING and maintaining the fences needed to control livestock is an expensive and time-consuming business. The materials alone can cost more than $20,000 a kilometre. On top of that, there is the cost of repairing damage caused by wild animals and falling trees. And then there is the need to move some fences around, a bit at a time, so that grazing land can be used efficiently. Strange as it may seem, many ranchers would therefore like to get rid of fences—if they could.

According to Dean Anderson, an animal scientist at America’s Department of Agriculture, and Daniela Rus, a computer scientist at the Massachusetts Institute of Technology, the answer is to move from real fencing to the virtual sort. The idea of virtual fencing is not entirely new. Pet “containment” systems, such as collars that give dogs a small electric shock if they roam outside a particular area, have been around since the early 1970s. But attempts to come up with a system for controlling free-ranging animals have failed.

Dr Anderson and Dr Rus started from the observation that the job of a fence is merely to regulate an animal’s behaviour and asked if there was another way of achieving the same end. The result is a device dubbed the Ear-a-round, which acts both as a sensor of what an animal is up to and as a discipline on animals that are not behaving as their owner wishes.

The Ear-a-round consists of a small, light box that sits on top of a cow’s head, and a pair of earpieces made of fabric and plastic. The box contains a small computer, a GPS satellite-tracking device and a transceiver that enables it to be programmed remotely. The earpieces both keep the box upright and deliver commands—either sounds or electric shocks—to the animal wearing the device. The whole thing is powered by lithium-ion batteries topped up by solar cells.

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The range that an animal is allowed to occupy is encoded using GPS co-ordinates. The GPS system determines the animal’s location, and an accelerometer and a compass housed inside the box track its rate and direction of travel. If an animal roams beyond the range specified, the device responds in a way determined by its wearer’s recent behaviour. The algorithms devised by Dr Rus are able to work out, based on past experience, how strong the message to turn back needs to be.

Minor transgressions lead to quiet sonic alerts or mild tingles; major ones to shouts or shocks. In both cases the cue is delivered to the ear opposite the direction that the animal is being nudged towards. Four years of research at a ranch in New Mexico have shown that cattle quickly cotton on to what they need to do.

Is all this really cheaper than fencing? At $600 a cow, not yet. But Dr Rus is working to get the price of the hardware down to the $100 that farmers will pay. Meanwhile Dr Anderson is about to start investigating how many cows actually need to be fitted with Ear-a-rounds to control an entire herd. He hopes that, by identifying a herd’s leaders and equipping them alone, this number can be reduced to a handful.

Not all the stimuli used to guide the animals are unpleasant—at least, not intentionally so. In April Dr Anderson set out to test whether a recording of him singing the “gathering songs” used during traditional round-ups would be as effective at herding cattle as irritating sounds such as barking dogs, or electric shocks. Four Brangus cows listened to recordings of him chirping “Come on, girls” at 30-second intervals. Almost immediately, he says, the herd began moving towards the corral. It is not clear whether they were encouraged by his singing, or were trying to get away from it.