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1 November 2007 Distance-based Criteria to Identify Minimum Number of Brown Bear Females with Cubs in Europe
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Abstract

Counts of females with cubs-of-the-year (FWC) have been used as an index for monitoring brown bear (Ursus arctos) populations or estimating a minimum number of adult females in several small and medium-sized populations. Because discriminating among family groups is crucial to this procedure, we sought to improve criteria used to differentiate among FWC using spatial and temporal distances between sightings. We used telemetry data from 11 FWC from southern and central Europe and 15 FWC from Sweden to determine the likelihood that observations were of the same FWC based on the distance moved and elapsed time period. Euclidean distances traveled by each FWC were estimated daily. We then calculated straight-line distances traveled by each FWC using intervals of 1–180 days, or the maximum available. We obtained the maximum values (highest percentiles) of distances over time for each FWC. We considered 2 periods of bear activity: early spring, from first observations after denning until 30 June, and the remaining active season from 1 July until the onset of denning. Native FWC living in the boreal forest of Scandinavia moved farther than those living in the temperate forests of southern and central Europe. Differences among FWC in southern and central Europe may be related to habitat characteristics and to the origin (native or released) of the bears we studied. For example, based on the upper 95% prediction interval of the curve fitted of the 80 percentile in the early spring–June period, 2 observations 30 days apart are unlikely to be of the same individual if >13 km apart for FWC in the boreal forest, >15 km and >7 km, respectively, for released and native FWC in southern and central Europe. Our findings may be useful for biologists and managers to help differentiate FWC and thereby estimate the minimum number of family groups present, particularly in areas with low densities of FWC.

Andrés Ordiz, Carlos Rodríguez, Javier Naves, Alberto Fernández, Djuro Huber, Petra Kaczensky, Annette Mertens, Yorgos Mertzanis, Andrea Mustoni, Santiago Palazón, Pierre Y. Quenette, Georg Rauer, and Jon E. Swenson "Distance-based Criteria to Identify Minimum Number of Brown Bear Females with Cubs in Europe," Ursus 18(2), 158-167, (1 November 2007). https://doi.org/10.2192/1537-6176(2007)18[158:DCTIMN]2.0.CO;2
Received: 29 August 2006; Accepted: 1 June 2007; Published: 1 November 2007
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