If you pay closer attention, you can see that some of the designs rely on very deliberate placements of circles; for example, eyes of the monkey and owl, and the nose of the whale.

Those are just the obvious ones that I can immediately spot — there was probably a lot of careful consideration into the placement of circles in order to facilitate good looking arcs and circles that bring the animals to "life".

Sure, you're not wrong. But a circle is just an arc of length 2pi * radius.