engleski

Movement patterns of female brown bears with cubs in Europe ; application to population monitoring

Counts of females with cubs of the year (hereafter, FWC) have been used as an index for monitoring brown bear populations and/or estimating a minimum number of adult females in several small and medium-sized populations. The goal of this paper is to improve the criteria to differentiate FWC using distance in space and time between sightings, since discriminating among different family groups is a usual constraint in this procedure. We used telemetry data from 11 FWC from South and Central (SC) Europe and 22 from Sweden to answer the question: “ What is the probability that after an observation of a FWC, this same family group has moved “ x” kilometers after “ y” days? Straight-line distances travelled by each FWC were estimated on a daily basis. Using moving windows, we calculated straight-line distances covered during intervals from 1 to 180 days, or the maximum interval allowed by the data, for each FWC. In a second step, maximum values (highest percentiles) of distances over time were obtained for each FWC. We considered two major periods of bear activity: spring, from first observations after denning until the end of June, and the remaining active season until denning. We used generalized linear models to distinguish groups of FWC according to geographical variables. Females living in the boreal forest of Scandinavia moved farther. Differences among FWC in the temperate forests of SC Europe appear to be related not only to habitat characteristics, but also to the different status (native/released) of the studied bears. In spring, 90% of the straight-line movements of FWC during 7 days were within 12.5 km, both for the females living in boreal forest and for the 5 females released in SC Europe. With the same percentage for 2 native females in SC Europe the distance is less than 2 kms. After spring, observations during 7 days were within 22 km, both for the females living in boreal forest and for the 60% of the released females in SC Europe. For the corresponding number of days and probability, the distance is as half as much, 11 km, for the native FWC and for the remaining released animals from SC Europe. A treshold of 11 kms includes 90% of locations for 83% of the native females of SC Europe (n=6) and 40% of the released animals in SC Europe, iregardless of lapsed time. In conclusion, these results can be a useful tool for biologists and managers for estimating the minimum number of family groups. However, this method does not allow calculating the probability that two observations close in space and time belong to different family groups. In this sense, the method is probably more useful in areas with low densities of FWC.

Movement patterns; female brown bears with cubs; Europe

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