Dispersion and Colonization
by Mezenc Marmots

Evolution of Total Number

The importance of a population can be evaluated by the total number, that is the total number of young and adults observed each year.

Such number has been established each year since 1988, according to five numberings per year.

The chart on the right shows the annual evolution of the number of marmots living around the Mezenc since 1988.
Owing to this chart two important establishments may be done:
1. On a general point of view, marmot population steadily increases. In order to better appreciate the dynamics of this increasing, we have calculated the statistical position parameters of this strength (median, mean, standard-error) as well as the increasing factor and the doubling time (see table here-under).
2. A more detailed look, let appear several demographic accidents during which population mor or less decreasese (see : Analysis of the demographic accidents ).

Descriptive Statistics of the l'accroissement marmot number increasing

Before 1989, the number of marmots observed has varied from 37 to 48 marmots.

From 1990 to 1999, the number of marmots observed has varied from 53 to 228 marmots.

From 2000 to 2009, the number of marmots observed has varied from 204 to 497 marmots.

Since 2010, the number of marmots observed has varied from 479 to 603 marmots.

PeriodMax Marmot NbMedianMeanTheoretic NumberIncreasing RateDoubling Time
Before 19894842.542.5 ± 43.21490.154.62
From 1990 to 1999228135.5131.9 ± 67.959180.332.1
From 2000 to 2009497297.5336.9 ± 167.717560.144.95
Since 2010603483.5511.8 ± 234.316060.0417.33
2010 Forecast594483.5xxx5940.061.21
2020 Forecast1106xxxxxx11060.061.52

Max Number of Marmots : it represents the maximum number of marmots observed during the related period.
Median : it represents the median number m of marmots observed during the related period.
Mean : it represents the mean number of marmots for the related period. Mean is completed by ± the standard-error.
Theoretic Number : it represents the maximum theoretic number of marmots for the period, calculated by multiplying the starting number of marmots N by the increasing rate during the number of years n of the period: NT = N * (1+TA)n
Increasing Rate : the increasing rate by period TA is calculated by substracting the number of marmots M(t) of the starting year from the number of the last year M(t+n). The increase [M(t+n) - M(t)] is related to the maximum number of marmots known during this period M(t) * n (with n = number of yearss) : TA = [[M(t+n) - M(t)] / M(t) * n
Doubling Time: is the number of years necessary to have twice more marmots, in an hypothesis of linear increase. It is approximated by the formula TD = ln(2) / TA.



Citation : Distribution of the Mezenc Marmots - © 2017, Le Berre M., Metral J. (ONCFS), Putz O. (LPO) & Ramousse R.
Last modification: 2016-05-10 13:10:38