European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

European bisons (Bison bonasus) are seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

Calves of European bison (Bison bonasus) are seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

A calf of European bison (Bison bonasus) is seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

Calves of European bison (Bison bonasus) are seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

A calf of European bison (Bison bonasus) is seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

A calf of European bison (Bison bonasus) is seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

Calves of European bison (Bison bonasus) are seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

Calves of European bison (Bison bonasus) are seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

Calves of European bison (Bison bonasus) are seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

Calves of European bison (Bison bonasus) are seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

A calf, left, of European bison (Bison bonasus) is seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)

European bison (Bison bonasus), wisent, European wood bison, calf

European bison (Bison bonasus), wisent, European wood bison, calf

Calves of European bison (Bison bonasus) are seen in the Olomouc Zoo, Czech Republic, on June 28, 2019. (CTK Photo/Ludek Perina)