News Animals

Male mammals aren’t always bigger than females

Biologists long assumed female mammals are usually smaller than males. That’s probably not true

Four brown horses wade in shallow water

In most equids, such as these feral horses wading in the waters of Shackleford Banks Island, N.C., there’s little difference in size between the sexes.

Daniel Rubenstein

By Jonathan Lambert

The idea that male mammals tend to be larger than females has been scientific dogma since Darwin. Bigger bodies, the thinking goes, are better in the battle to win the attention of choosy females.