Does dogs know Calculus?

From the article:

When Elvis and Pennings go to the beach, they always play fetch. Standing at the water's edge, Pennings throws a tennis ball out into the waves, and Elvis eagerly retrieves it. When Pennings throws the ball at an angle to the shoreline, Elvis has several options. He can run along the beach until he is directly opposite the ball, then swim out to get it. Or he can plunge into the water right away and swim all the way to the ball. What happens most the time, however, is that Elvis runs part of the way along the beach, then swims out to the ball.

Elvis playing fetch at the beach. Courtesy of Tim Pennings

Depending on the dog's running and swimming speeds, the strategy that Elvis follows appears to minimize the time that it takes to get to the ball. Indeed, Pennings found by experiment that Elvis performs in a way that closely matches a calculus-based mathematical model of the situation.

"It seems clear that in most cases Elvis chose a path that agreed remarkably closely with the optimal path," Pennings argued in the May 2003 College Mathematics Journal.

http://www.sciencenews.org/articles/20060218/mathtrek.asp