Whale sharks have a mouth that can be 1. 5 m (4. 9 ft) wide, containing 300 to 350 rows of tiny teeth and 20 filter pads which it uses to filter feed. Unlike many other sharks, whale sharks' mouths are located at the front of the head rather than on the underside of the head. Whale sharks have five large pairs of gills. The head is wide and flat with two small eyes at the front. Whale sharks are grey with a white belly. Their skin is marked with pale yellow spots and stripes which are unique to each individual. The whale shark has three prominent ridges along its sides. Its skin can be up to 15 cm thick. The shark has two dorsal fins and a pair of pectoral fins. Juveniles' tails have a larger upper fin than the lower fin, while the adult tail becomes semilunate. The whale shark's spiracles are just behind its eyes.