Male mammals aren't bigger than females in a majority of species.
Male rabbits aren't the same size as female rabbits
Experts at Princeton University compared the male and female body masses of 429 species and found that females were either the same size or larger than men 55 per cent of the time.
Species in which females are bigger include the domestic rabbit, the horseshoe bat and the golden hamster.
Scientists argue that the "larger male" idea could have developed because studies have often been carried out on "charismatic" animals where males are typically bigger - including lions, elephants and pandas.
First author of the study Dr. Kaia Tombak said: "A long-standing narrative postulates that in mammals, males are typically larger than females.
"Darwin treated it as a matter of common knowledge, as have many subsequent evolutionary biologists. It may be time to retire the 'larger males' narrative."