Student Papers
Raven and Johnson's Biology, Sixth Edition

Habitat Selection in Snowcocks

Student Research Project
Habitat selection of Himalayan Snowcocks in the mountains of Pakistan

Student
Jorge Lopez
Major: Zoology
Future Plans: Graduate school in evolution, ecology and/or behavior

Professor
Judy Stamps, Professor, Section of Evolution and Ecology, University of California, Davis

Animals are not randomly scattered across the landscape. Instead, most species actively choose certain types of habitats in which to live and raise their young. Habitat selection considers the types of habitats used by particular species, the behavioral processes that govern the choice of particular habitats, and the evolutionary reasons why the members of a species prefer some habitats to others. Habitat selection is a topic of more than academic interest because successful conservation efforts require accurate predictions about the habitats required and preferred by endangered species.

The first step in any study of habitat selection is to determine where animals are and whether their spatial distribution pattern reflects active habitat choice. Recently, Jorge Lopez had an opportunity to work in Pakistan, as field assistant to a graduate student in my lab. Before leaving, Jorge and I designed a project to study habitat selection in snowcocks, a chicken-sized bird that lives high in the mountains of Pakistan. Jorge's goal was to determine whether snowcocks randomly move among the habitats available in their range, or whether they actively prefer some types of habitats to others.

In the summer of 1992, Jorge traveled to Dhee Sar in the Karakoram Mountains of northern Pakistan. In the local language, Dhee Sar means "above where people live," an appropriate name for a study area 14,200 feet above sea level. Once there, he divided the available habitats into several distinct categories: ridge tops, rocky slopes, and valley meadows. He recorded every sighting of snowcocks in each habitat category, using an observation schedule that ensured each habitat was surveyed on a regular basis. He also mapped the study area to determine the percentage of area that was covered by each type of habitat. Additional information on temperature, snow cover, food production, predators, and snowcock behavior in each of these habitats was also collected.

Upon his return, Jorge and I analyzed his data and found that snowcocks strongly preferred the small flat areas on ridge tops. Although these areas comprised only 11% of the total area at Dhee Sar, snowcocks were observed on ridge tops 25 times more often than one would expect by chance, considering the size of ridge tops versus the amount of space covered by other types of habitats. Conversely, snowcocks visited meadows on valley floors less than one would predict by chance, even though their preferred foods were most abundant in those meadows. These results imply that food availability is not a primary determinant of habitat selection in snowcocks. Snowcocks may prefer ridge tops because these large, somewhat unwieldy birds evade eagles and other predators by flying downhill, so that ridge tops provide more potential escape routes than slopes or valleys. Thus, Jorge's study showed that snowcocks prefer some habitats to others and suggested hypotheses about the possible reasons for these preferences, hypotheses that could be tested in subsequent studies.

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