The main monograph on the grey wolf by Mech and Boitani (2003), which still provides the basic and unequalled knowledge on the species biology, informed the following. “Almost 30 years ago, Keith (1974) concluded that “the factors which provide wolf pup mortality during the first 5 months are almost wholly unknown. This is probably the single greatest enigma in wolf biology today.” Though some strides have been made toward identifying these factors, this is still a much-needed area of research.”
While reading this in 2004, we already were much aimed at the question. Moreover, the opportunity to find out something really new in the wolf biology accelerated these our research efforts. Nowadays, we may say that, at least, for the region of Belarus mortality in wolf pups is known more or less. Also, we assume that the factors, which impact the survival of wolf pups in Belarus, act in other regions of European forest zone. At the same time, we suppose that the only main causes of wolf pup mortality were found out, whereas many smaller questions remained without answers still.