Holarctic Marmots as a factor of Biodiversity.
Rumiantsev V.Yu;, Nikol'skii A.A. & Brandler O.V. eds.,
Abstracts,
3d Conference on Marmots (Cheboksary, Russia, 25-30 August 1997),
Moscow ABF 1997, 216p. : 190.
CORRELATIONS BETWEEN WEATHER FACTORS AND LIFE-HISTORY TRAITS
OF YELLOW-BELLIED MARMOTS
O.A. Schwartz*, K.B. Armitage**
* Department of Biology, University of Northern Iowa
** Department of Systematics and Ecology, The University of Kansas, Lawrence,
USA
Sixteen measures of life-history traits from known-age Marmota flaviventris studied from 1969 through 1986 were dependent variables in a partial correlation analysis with 15 measures of seasonal weather as independent variables. We considered weather data from the current year and from the previous year; i.e., the effects of weather in one year on life-history traits in the following year. All measures of weather were ranked from low (or early) to high (or late) and all life-history variables were ranked from low to high. Winter length (the time between the first snow fall in autumn and the last snowfall in spring) was positively correlated with the percentage of adult females breeding. Winter length (the time between the first snow cover in autumn and the last snow cover in spring) was positively correlated with the percentage
of the total population surviving the winter. The length of the growing season, measured from the last snow cover in spring to the first snow cover in autumn, was positively correlated with mean colony size, the variance in mean colony size, the percentage of the total population surviving, and mean litter size. The time of first snow cover was negatively correlated with mean age of maturity. The time of the first snowfall was positively correlated with the percentage of juveniles (all animals through age 1) and of non-maternal females surviving. The time of the last spring snow was negatively correlated with the variance in litter size. The number of frost free days was negatively correlated with the percentage of adults surviving and positively correlated with the degree of iteroparity. Mean precipitation was positively correlated with the percentage of juveniles surviving; the variance in precipitation was positively correlated with mean colony size and negatively correlated with mean age of maturity.
When weather data from the previous year were used, winter length (time between first and last snowfall) was positively correlated with the variance in mean colony size. Winter length (time between first and last snow cover) was negatively correlated with the mean and variance in mean colony size and positively correlated with the percentage of all animals surviving. The length of the growing season was negatively correlated with the percentage of adults surviving. The time of first snowfall in the previous year was positively correlated with the mean and variance of colony size. Last snow cover was positively correlated with the variance in colony size and negatively
correlated with the variance in litter size. Mean precipitation was positively correlated with mean colony size and percentage of females breeding and
negatively correlated with the percentage of adults surviving. The variance in precipitation was positively correlated with the variance in colony size and mean litter size and negatively correlated with the mean age at maturity. No measure of temperature was significantly correlated with any life-history variable for either current year or previous year analysis.
We suggest that length of growing season, length of winter, and precipitation are major weather variables affecting reproduction and survival.