National Geographic : 1991 Jan
guanaco comes feetfirst into the world in early summer after a gestation of nearly a year. Guanacos make up 55 percent of the diet of pumas, which tend to go after young guanacos, known as chulengos, and also hunt Euro pean hares and flightless rheas. Prior to ear-tagging a chulengo as part of our mortality study, a student assistant keeps the animal's mother away by returning her threat display (top right). Near our research station, Warren, at left, and I examine part of our collection of more than a thousand guanaco skulls. They help us determine cause of death, as well as age. Puncture wounds from pumas' canine teeth mark a third of the skulls; of those, 60 percent came from animals less than two years old. Male and female guanacos bunch up in winter, when grazing is patchy (below). For pumas, pickings are abundant.