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., 59-60 (Russian), 164 (English)


POPULATION DYNAMICS, MATING SYSTEM AND YOUNG SURVIVAL IN ALPINE MARMOTS (MARMOTA MARMOTA L.)


D. Lenti Boero

Corso di Laurea in Psicologia, Facolta di Scienze della Formazione, Universita degli Studi, Urbino, Italy


This study took place in the Parco Nazionale del Gran Paradiso (P.N.G.P.) from 1981 to 1993. Observations were done mostly from early June to late September. Marmots inhabited the concavities of the valleys above timberline, and slopes from 0 to 5 of a transect of 4200 ha. Density was estimated by animals counts in two sample areas and ranged from 0.6 to 1.5 an/ha. Population dynamics was investigated from 1985 to 1993 in a colony at 2350 m., where 57 marmots were live trapped for individual recognition. Total number of reproducers/year was 27, in the 18.5% of cases a triplet made of two unrelated males and one female was present. Never were two adult females found together and never were two different litters found on the same territory. Male/female ratio for immigration in the colony was 1.8, (G test = 7.916, df = 1, P > 0.005). Mean group size, not including infants, was 4.714 2.9, range 2-11. Group size was related to the number of infants born in the previous year (Regression, F = 8.4; df 1,26, P = 0.008). The social groups had the higher turnover rate ever reported for a colony of alpine marmots.

A total of 60 infants were born during the study. Mean litter size was 4 0.65, and median was 4. Mean number of litter sired per female was 1.5 1.77. Forty percent of the new pairs disappeared after their first overwintering with litter. Seventy four percent of infants whose parents were present in the territory were found in the following year as yearlings, but none of the orphaned infants were found (chi-square = 26.4, df 10; P < 0.003). Twelve parented three years old and three (50% of the corresponding cohort) orphaned three years were found respectively in the natal territory.No animal of four years of age was found in the natal group, independently of parents presence. No sex difference for permanence in the natal territory were found, and mean age of permanence was 2.29, (range 2-3). Predation was assessed on 8.7% of all individually marked subjects.

The high turnover rate is ascribed to the heavy predation pressure and to the harshness of the environment, and is considered the ultimate explanation for the fact that the permanence in the natal territory is sensibly lower than the one reported in other geographical areas.


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