Влияние выпаса на площадь индивидуальных учатков степного сурка (Marmota bobak Müll.). Effect of cattle pasture on home-range size of the steppe marmot (Marmota bobak Müll.) in northern Ukraine [Effet du pâturage sur la taille du domaine vital de la marmotte des steppes (Marmota bobak Müll.) en Ukraine du nord

Résumé

The study was carried out in 1994-1998 at a stationary site (about 90 km to the Northeast of Kharkov). 75 steppe marmots including 22 adult females and 34 adult males were captured and tagged. Eartags were used for a long-term identification search for additional possibilities of a reliable identification of marmots during all their lifetime we revealed on soles and finger phalanges in marmots of our stationary site some light-colored spots, the number, shape and location of which are probably of individual nature. Claws and fur round paws are often also of light color or absolutely white. Photos and detailed data in the field register book concerning the number, shape and location of depigmented parts of skin and fur, claw coloration, etc. permitted to identify the marmots which have lost their plastic tags (the ears of such animals bear characteristic holes). Out of 57 captured adult animals (including the repeatedly trapped ones) 45 marmots (79%) used the territory round the burrow of their capture, 7 (12%) were observed on the territories at different distances from places of their trapping and 5 marmots (9%) were never met again at the tagging site.The size of individual home-ranges were calculated using 95% confidence ellipses on the basis of the ELLIPS program developed by A.T. Terekhin, A.A. Nikol'skii and V.Yu. Rumiantsev. The comparison of result was performed wThe average individuals home-range size at the territory with a low anthropogenic pressure was 24985 m2 (from 9254 to 35573 m2). The individual center activity bias (for different animals) between the first and the second intervals ranged from 15 to 43 m. The home-range size of adult animals on the territory with moderate anthropogenic influence was on average 9622 m2 (from 3593 to 15495 m2) i.e. , 3.6 times less than in the firt case. The activity center bias varied between the intervals from 4 to 31 m. Similar values were registered for the territory of high anthropogenic pressure: the average size equalled 6124 m2 (from 1899 to 15534 m2), the activity center bias was from 4 to 20 m.The number of adult animals whose individual home ranges partially overlapped (more than by 50%) was from 2 to 5 (3 on the average). Individual home ranges on the territory of low anthropogenic pressure are more stable and occupy larger areas than those on territory of moderate or high anthropogenic influence. The activity center bias is also a highest one on the territory of the first type, which reflects the fact of a seasonal using burrows of different biological destination by animals as well as their choosing foraging areas with different vegetational associations. The size of individual home ranges is, most probably, connected with the mutual dislocation of foraging areas and permanent burrows.