Are platypus females bigger than males?

Apart from the obvious reproductive differences, the main physical difference between male and female platypuses is that the female is considerably smaller.

While both males and females have a spur on their hind ankle when young, the female's spur falls off before she is a year old, and the male's becomes his primary defence, with a debilitating venom.

The female platypus has sole responsibility for the raising of the young platypuses. The male has no part in raising the young platypuses.