Restoration and intensive management have no effect on evolutionary strategies

M. Hayward, R. Kowalczyk, Z. A. Krasinski, M. Krasinska, J. Dackiewicz, T. Cornulier

Research output: Contribution to journalArticlepeer-review


The European bison Bison bonasus is the largest extant terrestrial mammal on the European continent; however, the species went extinct in the wild in 1919. Restoration started in 1929 in Poland’s Bialowiez¿a Primeval Forest using captive individuals sourced from zoological gardens and breeding centres. Of the 7 founders, 2 individuals contributed 85% to the genetic make-up of the lowland line of the species. The Bialowiez¿a bison population numbered 820 in 2008, but very low genetic diversity and a high level of management have raised questions as to whether it still conforms to evolutionary predictions. We tested whether the sex ratio of European bison calves conformed to the Trivers-Willard hypothesis at the population level, i.e. whether it became increasingly female-biased as bison condition deteriorated following increased population density. We found that increased population density and reduced female body mass led to increasing female-biased calf sex ratios, whereas mast years (abundant food resources) corresponded to male-biased sex ratios. Despite the high degree of inbreeding and management, European bison are still responding as expected to variations in female body condition; however, the precautionary principle cautions managers of small populations that artificial selection can alter the evolutionary strategy of wildlife even though we did not detect this in theBialowiez¿a bison population.
Original languageEnglish
Pages (from-to)53-61
Number of pages9
JournalEndangered Species Research
Issue number1
Early online date21 Oct 2011
Publication statusPublished - 21 Oct 2011


  • body condition
  • local resource competition hypothesis
  • maternal investment
  • reproductive success
  • sex ratio manipulation
  • Trivers-Willard hypothesis
  • European bison
  • ungulates


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