Some factors influencing reproductive parameters of European bison cows


  • Katarzyna Daleszczyk Białowieża National Park, Białowieża


Bison bonasus, reproduction, fecundity, sex ratio of offspring, maternal investment


Reproduction is one of features important for species survival that may be affected by various factors. In this study were analysed reproductive parameters of female European bison based on the long-term data from the captive breeding centre in Białowieża National Park. The study focused on looking for factors influencing fecundity and the sex of offspring and an attempt was made to estimate differences in costs of raising daughters versus sons. Age of bison females influenced significantly their fecundity, with cows 5–13 years old being most fecund. Age at first calving did not affect the fecundity coefficient based on the entire reproductive lifespan of a female. No correlation was found between the fecundity and inbreeding coefficients of a cow. There was no difference in the mean age of cows giving birth to male or female calves. Calving date influenced the reproductive status of a cow the next year. Cows calved on average 39 days later before barren than before parturient years. On the other hand, reproductive status of the cow influenced her calving date in the next year. Calves were born on average 38 days later after parturient than barren years, indicating the cost of reproduction borne by mothers of all calves. However, sex-biased maternal investment was not found. The sex of a calf did not influence the
reproductive status of the female or the sex of the calf born next year. The length of interbirth intervals after birth seemed to be influenced more by individual variation of cows than by the sex of their offspring. No difference was proved in the length of interbirth intervals before the birth of calves of different sex, so the length of gestation and prenatal investment seem to be similar in both sexes. Analysis of birth sex ratio of offspring of various cows revealed that ratios were not homogenous among the progenies and data as a whole did not fit the expected sex ratio 1:1; however, factors influencing it were not found. There was no correlation between the inbreeding coefficient of a female and birth sex ratio of her offspring. Further research on factors affecting European bison reproduction is needed and should include a variety of external factors. 




How to Cite

Daleszczyk, K. (2022). Some factors influencing reproductive parameters of European bison cows. European Bison Conservation Newsletter, 4. Retrieved from



Peer-reviewed articles