Mortality of European Bison, American Bison and Complex Hybrids in the Prioksko-Terrasny Reserve Breeding Center

Abstract

AbstractThe authors compared the materials of pedigree books and acts of death of three groups of animals: European bison (Bison bonasus), American bison (Bison bison) and complex hybrids (Bison bonasus + Bison bison + Bos taurus), which died on the territory of the European bison breeding center of the Prioksko-Terrasny nature reserve during the period from 1948 to 2020. Comparison of data on perinatal mortality in the period 1948–1980 shows a slight difference between the three species of animals: 9.6% in European bison, 11.4% in American bison and 6.9% in complex hybrids. The survivability rate over 1 year among young animals during the same period was 85% for European bison, 88.6% for American bison and 87.4% for complex hybrids. The main cause of death in all three groups is injuries, mainly caused by other animals in the herd. In second place are the cases of perinatal mortality. Complex hybrids showed slightly better indicators in perinatal mortality than the groups of purebred animals, however, it was in hybrid females that an increase in the frequency of deaths during childbirth was recorded (6–7 times more often compared to European bison). The analysis shows a decrease in perinatal mortality and an increase in the survivability rate of young animals among European and American bison in the period after 1980. Perinatal mortality among European bison decreased from 9.6% to 7.3%, and the 1st year survivability rate increased from 85% to 88.6%. Perinatal mortality in American bison decreased from 11.4% to 6.8%, and the survivability rate increased from 88.6% to 90.4%. Improvement in the period 1981–2020 compared with 1948–1980 was due to the improvement of veterinary practices, the implementation of antihelminthic measures and the optimization of the diet in the breeding center. It is also possible that the statistics was effected by the underestimation of the deaths of young animals and perinatal mortality. In total over the whole period from 1948 to 2020 perinatal mortality among European bison in the breeding center reached 8,2% and 1st year survivability 87,1%. These numbers for American bison were 8,3% and 89,9% respectively.KeywordsEuropean bisonMortalityPrioksko-Terrasny reserve