Localized by one (or several) burrow, a marmot site remains conspicuous for a very long time. Its occupation is not necessarily permanent: resident marmots may die or emigrate...
Consequently, it is necessary to know, by periodic counts (5 times per year since 1988), weather a site is occupated or not.
The opposite chart shows the relation between the number of sites observed each year (upper line) and the number of sites really occupated each year (lower line). The reciprocal evolution of these two lines indicates that all the sites are not permanently occupated. For that, we have to calculate an occupation factor for each site (visible at the bottom of each site card) as well as an annual occupation factor for the whole sites (following page).
