How do hedgehogs differ from echidas?
Hedgehogs give with birth to live young and echidas lay eggs.
Echidas are not related to hedgehogs. Usually, echidas are compared
to (but not closely related to) porcupines and anteaters. Echidas
are close cousins to the platypus, the only other egg laying
mammal. Both the echidas and the platypus (they are called
monotremes) are found only in Australia. Monotremes have milk ducts
(pores) that allow them to feed their young. Monotremes do not have
nipples like other mammals.