The greater sage grouse, a bird native to North America, has an elaborate courtship ritual. Every year, males congregate at locations known as "leks" to perform competitive mating displays to entice females to copulate. Each mating display, in which the male performs a series of ritualized movements and sounds with his air sacs inflated, is referred to as a "strut." These "struts" are typically performed one after another in quick succession, in what is referred to as a "bout." Mating success is highly skewed, with a percentage of birds never once mating and a privileged few mating dozens of times.
In studies that seek to understand why some individuals are so much more successful than others, researchers have often counted the total number of display events or averaged the lengths of the intervals separating displays within a bout. "These 'bout agnostic' analyses collapse each animal's multidimensional display effort into a single metric, potentially discarding important information," Perry and her coauthors write.
Perry - Hidden - Markov - Model - Hand
Perry's custom-built hidden Markov model, on the other hand, offered several advantages over simpler models. For one, it accounted for differences in display persistence -- characterized by the number of "struts" that a sage grouse does in a row -- as well as the length of time that males rested between struts in a single bout. It also enabled Perry and her coauthors to analyze whether males' display tactics changed depending on the presence and behavior of females.
Strut events were recorded using high definition cameras and on-site observations at three leks in Fremont County, Wyoming. At each location, male display activity was tracked when no female was present, when a robotic female was present and showing either "interested" or "uninterested" behavior, and in the presence of real female sage grouse. "Most males...
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