Home range area and shape of yellow-bellied marmots

Abstract

Home range is the area that marmots use to obtain food and burrows necessary for growth, reproduction and survival. During regular censuses, the position of each marmot was recorded as a pair of coordinates from a calibrated grid overlain on a photograph of the colony site. Home range area was calculated as the product of the area of a grid square multiplied by the number of grid squares a marmot utilized. Clearly identified excursions were not included in the calculation of area. Shape was determined as the outline of the home range. The analysis included 24 years, four ages, two sexes, four colonies, four categories of residency, and whether an individual engaged in excursions. A general linear model ANOVA revealed that year (P > 0.001), age (P > 0.001), residency (P > 0.001), and colony (P > 0.001) significantly affected home range area but that sex (P = 0.373) and excursions (P = 0.312) did not. Shape was affected mainly by topography and the presence of other marmots. Area increased with age: adults < 2-year-olds < yearlings < young. Territorial males had the largest area followed by adult females whose area was larger than that of yearlings. Home range varied among colonies. Young and transients made the fewest excursions; adults, the most. Excursions were more frequent in the largest colonies. Residency was significantly affected by age, colony, sex, and excursions. Dispersers and transients were male-biased; residents were biased toward females and young.