MORTALITY ESTIMATION OF EUROPEAN BISONS (Bison Bison bonasus L. 1758) IN 1937 - 1955
This article is focused on the time between 1937 and 1955. The data for the analysis of the bison mortality at this time are quoted from the official genealogical books published in 1947, 1949, 1953 and 1955. Four major age categories are considered in the article: a) newly born calves, b) 2 months old calves, c) under 1 year old, d) older than 1 year. This category principle applies to the mortality analysis of both male and female calves. The Pedigree Book keeps records about mortality of a great number of calves, but many of them have no date of birth. This lack of information is the biggest problem for the estimation of mortality and average life expectancy analysis of the bison at that time. The record book for the time between 1939 and 1955 gives 456 bison calves, 280 of which have a birth date and 176 have no date. At the same period of time there were born 435 calves: 212 female and 223 male ones. Male calves 29 (43,28%) died on the day of birth, 19 (28,36%) died during 2 months after birth, 19 (28,36%) died by the 1 year age. The average male calves life expectancy of the age above 1 year is 4,69 years. Female calves 10 (15,38%) died on the day of birth, 33 (49,25%) %) died during 2 months after birth, 22 (33,85%) died by the 1 year age. As for the calves with unknown birth date, there died 77 male calves and 87 female ones.