Home range area and shape in yellow-bellied marmots [Surface et forme du domaine vital chez les marmottes à ventre jaune].

Résumé

Home range is the area that animals traverse to obtain resources necessary for growth, reproduction, and survival. For marmots, the major resources are food and burrows. I investigated the relationship between five factors and home range area (N=792). 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 was the product of the area of a grid multiplied by the number of grids a marmot utilized. Excursions, when clearly identified, were not included in the calculation of area. The analysis included 24 years, four ages (adult, two-year-old, yearling, young), two sexes, four colonies (Picnic, North Picnic, River, Marmot Meadow), four categories of residency (adult female, disperser, territorial male, transient), and whether an individual engaged in excursions (yes or no). A general linear model ANOVA revealed that year (p=0.000), age (p=0.000), residency (p=0.000), and colony (p=0.000) significantly affected home range area but that sex (p=0.373) and excursions (p=0.312) had no effects. Shape was affected mainly by topography and the presence of other marmots. Area decreases with age:adults > two-year-olds > yearlings > young. Territorial males had the largest area followed by adult females > dispersers, but area did not differ between dispersers and transients. Home range area varied among colonies: Picnic > North Picnic > River > Marmot Meadow. Young and transients made the fewest excursions; adults, the most. Excursions were more frequent in the largest colonies and less frequent among transients. Residency was significantly affected by age, colony, sex, and excursions. Dispersers and transients were male-biased; residents were biased toward females and young.