BEOBACHTUNGSHAUFIGKEITEN VON WILDEN BRAUNBAREN 



1147 



hunting season (fig. 2 a = hunters' observations, b = observations of non- 

 hunters) and the kind of observation (fig. 3 a = sightings, b = droppings, 

 c ^ tracks, ci =■- damages to farmers, mostly sheep) are discussed, but with one 

 exception (fig. 3 d) the gênerai pattern remains the same. We believe that the 

 best hypothesis to explain ail our frequency distributions is a fluctuation of 

 movement-activity with a high in May and autumn. The following équation is 

 given: 



^(F, t) = ^Beob. ^Bàr 2 d {VBeob.+ ^ Bar) 



where E^p^ ,) = expected number of bear sightings on the area E considered in 

 the time interval Db^^j, = density of observers, D^^y ^ density of bears, 

 d mean observation distance, Vg^^f, = average movement activity of observers 

 (^'speed", e.g. km per month), F^^y = the same for the bears. In this équation 

 spacial heterogeneties, eff'ects of bear and man not having the same activity 

 periods (bears are mostly active at night) and the tendency of bears to hide from 

 men are not considered or assumed to be constant respectively. 



The sightings of more than one bear in a group, thought to be mostly sows 

 with cubs not participating in reproduction for that year, show the same pattern 

 as the other distributions (fig. 5). This seems to suggest that breeding is not the 

 only factor causing thèse fluctuations in movement activity. 



Based on the arbitrary assumption that the winter denning period occurs in 

 those winter months in which 5 % or less of the observations are made, Vv'e postulate 

 that the bears den from December to March (inclusive) in the Trentino. 



RÉSUMÉ 



836 observations d'ours (y compris les empreintes et les déjections), émanant 

 des renseignements de 226 personnes sont classées chronologiquement par mois. 

 La répartition des fréquences qui en résulte — également en ce qui concerne les 

 types d'observations consignées — montre une bimodahté avec un premier 

 maximum mensuel en mai et un second sommet, plus étalé, en octobre (rarement 

 en septembre et en août). 



Plusieurs suppositions amènent les auteurs à considérer une phase d'activité 

 maximale des ours en mai et en octobre. Avec tout au plus 5% des observations, 

 on peut déduire que l'état de « torpeur hivernale » tombe sur la période de 

 décembre à mars. 



LITERATUR 



Barigozzi, c. 1963. Tentativo di Stima Numerica degli Orsi Bruni del Trentino. Istituto 



Lombarde (Mailand), (Rendiconti Classe di Scienze) (B) 97: 19-32. 

 Couturier, M. A. J. 1954. L'Ours Brun. Selbstverlag, Grenoble, 904 p. 



