Biology
Energetic Trade-offs of Diel Vertical Migration in Zooplankton
Quick fact
Some copepods migrate from 500 meters deep to the surface and back each day—a round trip that costs them over 30% of their daily energy budget, but it helps them avoid visually hunting predators like fish that forage near the surface during the day.
Why this is interesting
Every night, billions of tiny animals swim hundreds of meters toward the surface, only to retreat back into the dark before sunrise. Why would they spend so much energy commuting when they could just stay put?