engleski

The Early Gonadal Activity in Croatian Brown Bears And Its Management Implications

The aim of the study was to get insight in the age span of brown bear reproductive activity by morphometric and histological examination of gonads, and to test the management implications of findings by using two-sex matrix modeling. The reproductive span of the bear’s life is one of the critical parameters for population dynamics, with the age of the first reproduction as the important single factor. For brown bears in Croatia, as a standard, we use the age of four years as average for the first reproduction. In this pilot study, we examined testicles and ovaries of 30 hunted or traffic-killed bears (23 males, 7 females) in Croatia in 2012-2014 period. We measured length, width and mass of each gonad and by histological inspection determined its activity and maturity. Average length of mature testes was 6.52 cm, width 3.16 cm and mass 63.5 g. Juvenile and old inactive testes in average were smaller then active ones: 16.8 g vs. 49.8 g, respectively. Average length of ovaries was 2.36 cm and width 1.7 cm. We calculated correlation index between total testicles mass and body mass of each bear. In sexually active bears index was in average 0.85 (range 0.45-1.34), in two young bears 0.42 (range 0.39-0.45) and 0.31 in one old bear (of 325 kg body mass) with inactive testicles. Histological findings discovered inactivity of the testicles in the second year, but the first signs of gonadal activity and maturity were present in the third year of a male’s life, which implicates potential reproductive activity in the nearby mating season. Results from a previous study revealed that ovaries from 2 females held in captivity were active in their third year as well. If the animals from 3rd-year age class were included as reproductive in the matrix model, results showed that increase in recruitment to effective/reproductive population size for Croatian management system could be 12.8-16% for males and 10.9-11.4% for females. Accounting the maturity of gonads to all other characteristic that can influence the reproductive success, can help answering the question how large can be the „effective population size“ and how much mortality, hunting in particular, can be compensated.

gonadal activity; brown bear; Ursus arctos; management

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