A Fence You Cannot See
1Ridgeline Farm grows wine grapes and hay and raises beef cattle and sheep. The farm, the people and the numbers here are made up, but they are based on real farm studies. This summer, sixth grader Wren Castellano worked with farmer Aurelio Mendes and kept records for two projects about how farm animals sense the world and learn.
2The first project tested a virtual fence on a hillside pasture. Each of the 10 cows in the herd wore a collar with a small speaker and a satellite location finder. Mr. Mendes drew a boundary line on a map on his tablet. When a cow walks up to the line, its collar plays a beep. If the cow turns back, nothing else happens. If it keeps walking toward the line, the collar gives a mild electric pulse, weaker than the shock from an ordinary electric fence. Each collar counts its beeps and pulses.
3The second project was in the vineyard. Sheep can graze the grass and weeds between the rows of vines, but many sheep also like to eat grape leaves. Before the sheep went in, the farm's vet trained half of the flock. Each of those sheep was offered fresh grape leaves, and after it ate some, the vet gave it a safe dose of a substance that upsets the stomach for a few hours. The other half of the flock was not trained.
4To check the training, the vet put each sheep alone in a pen for 30 minutes with a pile of fresh grape leaves and a pile of grass, then weighed what was left. Each group had 10 sheep. The trained sheep were tested a week after training and again three months later.