Long-term population records - A crucial factor for the success of the re-establishment of European bison (Bison bonasus) population in Ukraine

After the elimination of last bison in the wild between 1919-1926, successf ul re-introduction of this species in Ukraine started in 1965. Animals orig inated from various breeding centres in Russia, Byelorussia, Lithuania, and Crimean Peninsula. Introduction took place in 4 sites in die Carpathians, and in 7 lowland parts of the country. After an initial growth of the popul ation, a decline in bison numbers is observed since the mid-nineties. At pr esent, there are 489 bison in Ukraine, in 11 free - ranging herds of size v arying between 3-148 individuals. At least two of them are at critical situ ation. Mortality results mostly from poaching, over-hunting and some endemi c diseases. Unknown remain also genetic aspects like the level of inbreedin g - potentially limiting reproductive success, or contributing to lower sur vival rate. Among tire most important aspects is potential crossbreeding of animals belonging to pure lowland Bialowieza line, with those of mixed low land - Caucasian descent. That may become a major threat for a significant part of original gene pool of European bison. Sound management of the free- ranging bison is at the moment possible only on the basis of detailed exami nation of existing bison records, pedigree books etc. The analysis of long- term records on the origin of a herd, sex composition, breeding history etc . is necessary to create the data base necessary for further exchange of in dividuals, designing supplementing procedure for threatened herds, and re-i ntroductions connected with the program of European bison re-establishment in the Carpathians and Ukraine.