Life history traits come in matched sets
- The idea
- Predict
- See it
- Why
- Check
The idea
“When animals have lots of babies, most of them survive. Species that care for their young bounce back fastest.”
More babies sounds like more survivors, and caring parents sound like a quick comeback. But care costs time and energy, so caring parents raise fewer young, more slowly.
The short version
The mistake: When animals have lots of babies, most of them survive. Species that care for their young bounce back fastest.
What's actually true: Most of a big brood dies, most of a few cared-for young live, and species that breed early recover first.
- A parent has a limited energy budget. Split it among hundreds of young and each gets very little, so most die early. That's a type III survivorship curve.
- Put the same budget into a few large young and care for them, and most of them survive. That's closer to a type I curve.
- Recovery speed comes from how soon and how often a species breeds. Fast maturity and big litters win, even when most young die.
On the exam: Many young means most die and numbers rebound fast. Few young means most live and recovery is slow.