St Louis Zoo is planning to add a US$80m (€70.6m, £62.4m) expansion which would house a new breeding facility as well as new outdoor visitor experiences.

According to the zoo's president and CEO Jeffrey Bonner, the breeding facility is expected to open in 2021, while the outdoor attractions are likely to be added after that.

The project had a boost earlier this month, when St Louis voters passed a motion to allocate funding to the project in a ballot via a sales tax scheme.

The sales tax increase will raise US$20m (€17.7m, £15.6m), with property taxes for the zoo equalling that.

"It needs more funds," said Ben Uchitelle, former chair of the Zoo-Museum District's board of directors, "but there are several better ways to raise those funds."

Admission to the zoo is currently free, but it is likely that the new facility would command a charge for entry to make it profitable.