MORTALITY DYNAMICS AND CAUSES IN BISON BONASUS AT THE FARM OF THE OKSKY NATURE RESERVE

Abstract

We have analyzed postmortem examination reports on 134 bison found dead at the farm of the Oksky Nature Reserve from 1960 to 2013. Bison mortality rate in four age-sex groups was studied. Prevailing causes of mortality were expressed as per cent of total rate. It was determined that mortality rate among bison at the farm of the Oksky Nature Reserve varied 2.0 to 10.2% of total population, averaging to 5.9% annually. At the same time, mortality among calves below one year old was 53.9%; among animals of 1 year to 4 years old - 15.6%; among bison of reproductive age of 4 to 15 years - 15.6%; and among old bison over 15 years old - 14.9%. Injuries were the prevailing cause of death among bison making up to 48.5% of mortality, followed by helminthosis with 8.2%; the goes gastrointestinal diseases contribute another 6%, and death of new-born calves due to umbilical cord rupture or agalactia in cows - 6% and 6.7% respectively. Resulting opinion was that a complex system of preventive veterinary and procedural actions to promote farming healthy animals without impeding their natural resistance to diseases. It is possible to decrease incidence ratio of fatal injuries by forming maintaining optimal number of animals in breeding groups, avoiding overcrowding and overpopulation of bison in the enclosures, building up groups farms to the places of reintroduction into the wild.of animals with due consideration of hierarchy. It is also necessary to ensure timely dispatch of bison from the farms to the places of reintroduction into the wild.