Acknowledgements
We thank professor Eugeniusz Żukowski for his help with the FORTRAN WATBUG program, and Ewelina Hapunik, MSc, for help in browsing the zoological collection at the Institute of Mammal Biology in Białowieża. Lara Keicher, Jenna Kohles and Ewa Komar commented on the previous version of the manuscript. We did not receive any grants to conduct this research.