National Geographic : 1972 Apr
heat again within six to nine days of giving birth, although my observations showed that only 5 of the 51 jennies had two foals within a two-year period. Still, if the life-span of wild burros ap proaches that of domestic donkeys-about 25 years-the animals have a potentially high rate of multiplying, and this has raised the specter of burro population explosions. Among the females I observed, however, only about 30 percent had new foals. Adult males, apparently because of dispersal to other areas, decreased by 45 percent, and the total population declined from 211 to 201. Of course my study was limited in territory. A comprehensive investigation of population growth and dispersal patterns is needed to determine the animals' long-range impact on the whole area. One evening in early summer, the season when most foals are born, I was invited to dine with Ranger Earle Curran and his wife Rachel at Emigrant Ranger Station. They asked about new foals. "I've counted six, including a brown-and white female paint," I replied. "That makes four spotted burros in this district." Mother Wants No Visitors The mother of the paint was Boldface, a brown burro with a white stripe down her nose (below). Although normally tolerant of my presence, Boldface would not let me come too close for the first five days, and I had to do my watching through a telescope. If I got within 50 yards of her foal, she gave a warn ing snort and trotted off, with her baby fol lowing close behind. The foal spent a great deal of time lying down or sleeping, but at intervals of 15 to 20 minutes she would walk up to Boldface to nurse. After five days Boldface refused to allow her offspring to nurse that often, and the little burro began eating spiny plants.