By Juan Mayorga In the grasslands of Yagul, in the central valleys of southern Mexico’s Oaxaca state, a jaguar makes its way through the bushes. It stops suddenly, lowering its head and sharpening its gaze, stalking. With its eyes on its target, it stealthily pounces on it. Just a short run and a jump before the jaguar’s prey is in its jaws. It sounds like a hunting scene from the wild, but this one is an exercise planned by a team of biologists, veterinarians and ethnologists. The prey isn’t a live animal, but a jute sack stuffed with chicken meat, strung from the end of a pole. The exercise …