The platypus uses its distinctive bill to paddle for molluscs, chiefly mussels and snails, on which it feeds. It lives by the water, building tortuous burrows in the riverbanks where it nests. The female remains in the nest (which may be lined with gum leaves) until the young hatch, a process that takes about two weeks. The platypus usually lays two eggs at a time which are 1.6–1.8 cm (0.5 in) in length and 1.4–1.5 cm in diametre.