engleski

Brown bear litter sizes in Croatia

Based on 116 observations of 105 brown bear (Ursus arctos) family groups of sows with cubs in the bear range in Croatia we calculated the mean litter sizes and the maximum survival rate. In addition to the number of cubs, each record contained information on the sighting date, age of cubs (cubs of the year or yearlings), and location (bear feeding sites or other places). Duplicated observations (N=13) have been recorded but were excluded from calculations unless belonged to different years (N=2). One historical record of 5 cubs found in a disturbed den on 13 January 1880 was also excluded from calculations. The mean number of cubs of the year was 2.39 (N=56, range 1 to 4, median=2), and the mean number of yearlings was 1.94 (N=49, range 1 to 4, median=2). The negative difference of 0.45 (16.9%) was significant (P0.001, t test). Probably the loss of cubs over their first winter was larger than 16.9% as the mothers that lost entire litter could not have been determined. The differences of numbers of cubs in spring and fall of the same year have not been significant. In 12 cases yearling cubs were seen with their mothers in fall, but only one observation of two years old cubs (N=3) accompanying mother has been recorded on 26 April 1999. The same female chased her cubs away already before 04 May 1999. This strongly suggests that the average litter interval for adult females was 2 years. Surprisingly, significantly more (P0.048) cubs of all ages were observed with mothers away from feeding sites (mean=2.33, N=48), compared to observations at feeding sites (mean=2.05, N=59). The calculation of mean litter sizes until 1989 compared to the ones from 1990 to 1999 showed no statistical difference: 2.19 (N=26) vs. 2.17 (N=81), respectively. The latter two calculations suggest that the recent practice of feeding bears in Croatia for the management purposes, so far, did not influence the bear reproduction.

brown bear; litter size; Croatia

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