Bison play in the snow as employees of the Chippewa Falls Parks and Recreation department use a front-end loader to clear snow in a small area of the bison pasture at Irvine Park on Wednesday, December 14, 2016.

CHIPPEWA FALLS – A newborn bison is running through the fields in the Irvine Park zoo. The tan-colored animal – born a couple weeks ago – brings the number of bison in the park up to seven.

It is always worth celebrating a birth at the zoo – breeding animals in captivity can be challenging. The park’s zoo staff deserves praise for its work in caring for all the animals year-round, and creating the nurturing environment that allows for newborns to survive and thrive.

However, the birth of another bison is particularly good news.

A virus wiped out nearly half the bison herd in Irvine Park in September and October 2013, with four of the nine animals dying from Malignant Catarrhal Fever, which causes an inflammation of the mucus membranes and has no cure. It was apparently transmitted to the bison by desert sheep that arrived in the park at the end of May 2013. Once the sheep were identified as carriers of the disease, they were immediately removed from the park, but it was too late to stop the deaths of four bison.

Parks director Dick Hebert previously said he generally doesn’t call attention to newborns in the park.

“We don’t, because we want to make sure everyone is healthy,” Hebert said. “Especially for the mother, because they are protective when they have their babies.”

They don’t always survive – one that was born in June 2016 died a couple days later.

In general, newborn animals are shipped out of the park as soon as they are able to part from their mother. This is because the adult males often become territorial and aggressive. For instance, the two bison born in spring 2016 were later removed.

According to city records, the bison pasture was added to Irvine Park in the 1920s.