Why is it that (on average and for most) fish, bird, and reptile species the females are larger than the males, but in mammal species the males are larger than the females? (Again, I am taking generally, on average.)

Question

I probably shouldn’t have included reptiles on this list. I got my fishes and reptiles mixed up haha

In: Biology

Answer 1

Some animals employ a quantity over quality offspring strategy. To produce more offspring, the females need to be larger to hold the offspring (usually in the form of eggs).

Mammals typically employ a quality over quantity offspring strategy. Nursing an offspring with milk requires the mother to be present. Since each female member of the species doesn’t produce many offspring, the best strategy for a male is to have many breeding females. Mammal species tend to have larger males because the toughest, strongest males are able to claim and protect a larger number of breeding females.