Clever Hans, the mathematical horse

In 1907 William von Osten toured around Germany with a horse, Clever Hans, that he claimed could perform various math problems. His story is found here: Clever Hans. While the feats of Clever Hans were debunked as an elaborate palor trick, scientists have found that many animals do have a sense for numbers. More recently, an article in Quantamagazine, highlights many true animal feats in recognizing different number of objects and even having a sense for zero.