For much of the time guanacos seem to live a sedate life, grazing alone or in small herds, or lying among the grasses to languidly chew the cud. But, we were there at the start of the mating season, when things sometimes got a lot more frisky. Males become territorial at 4 to 6 years old, and thereafter they engage in violent competition to establish residence in feeding territories and control of family groups. Although guanacos are not sexually dimorphic in body size, males have significantly enlarged canines, which they use in intense, frequently injurious male–male fights that include include spitting; threatening displays; chasing and fleeing; biting at the legs, hindquarters, and necks of their opponents; ramming chests; and neck wrestling. [Click HERE for a BBC video]

Guanacos live in herds composed of females, their young, and a dominant male. Bachelor males form separate herds. While reproductive groups tend to remain small, often containing no more than 10 adults, bachelor herds may contain as many as 50 males.The members of one particular herd with territory near the park entrance were particularly prone to engage in fights. I was able to photograph many examples of these behaviors over two days, usually positioning myself in a small depression to try to catch the guanacos on ridgelines so they would stand out against a clear or well-blurred background.