How much energy does it take to make a baby? Researchers are rethinking what they know
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In sheep, indirect costs account for an estimated 98% of the energy required to make a lamb. Credit: Klein & Hubert/Nature Picture Library
Elephants are pregnant for up to two years. Females of some fish species starve for weeks while holding dozens of eggs and hatchlings inside their mouths. And pregnant humans commonly endure months of fatigue and nausea. These are just a few ways in which reproduction demands energy from mothers across the animal kingdom.
But researchers might have vastly underestimated the energy it takes to reproduce, according to Dustin Marshall, an ecologist and evolutionary biologist at Monash University in Melbourne. Australia.
The extra energy it takes a human to produce a baby could be as much as 24 times more than some influential mathematical models had estimated, suggest Marshall and his colleagues in a study published in May1. For animals that rely on external heat sources to regulate their body temperature, called ectotherms, the difference is smaller. For the pampas snake (Tomodon dorsatus), for example, the value is around four times more. And for a species of seawater fish called the capelin (Mallotus villosus), it is twice more.
