Summary
The time and energy a parent spends on offspring, typically higher in the sex that produces fewer larger gametes.
In depth
Robert Trivers: the sex investing more is choosier; the other competes. Investment includes gamete size, gestation, feeding and protection.
Investment in current offspring reduces the parent's future reproduction. The sex with greater investment tends to be limiting and choosier, which shapes sexual selection.
Remember: sex roles can reverse when males invest more, as in pipefish.
Parental investment, defined by Trivers, is any parental expenditure that raises offspring survival at the cost of the parent's ability to invest in other offspring. The sex that invests more, typically females with large eggs, is usually choosier, while the other sex competes for access.
Investment ranges from gamete production to nest building, guarding, feeding and teaching. Sex roles can reverse: in seahorses and jacanas males care for the young, and females compete for mates.
Example: elephant seal males fight for harems while females provide months of milk.
Frequently asked questions
What is Parental Investment?
The time and energy a parent spends on offspring, typically higher in the sex that produces fewer larger gametes.
Which area of biology covers Parental Investment, and how advanced is it?
Parental Investment is one of the 53 topics in Animal Behaviour. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Mating Systems, Dominance Hierarchies, Sperm Competition.
Why does Parental Investment matter?
It predicts which sex is selective, and shapes ornaments and fighting.
Can you give an example of Parental Investment?
Seahorse males brood young, and females compete for males.
What should I learn before Parental Investment?
Work through the Beginner topics in Animal Behaviour first, such as Animal Behaviour, Innate Behaviour, Learned Behaviour, then return to Parental Investment. Intermediate topics assume the Beginner vocabulary.
What topics are related to Parental Investment?
The closest topics to Parental Investment are Mating Systems, Dominance Hierarchies, Sperm Competition, Imprinting. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Parental Investment?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Parental Investment. To practise the whole of Animal Behaviour, use the Animal Behaviour quiz.
How is Parental Investment different from Mating Systems?
Parental Investment: The time and energy a parent spends on offspring, typically higher in the sex that produces fewer larger gametes. Mating Systems: Monogamy, polygyny and polyandry reflect resource distribution and parental investment. Read both side by side and note what each one explains.
How should I study Parental Investment step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Mating Systems and explain the difference aloud. Finally, take the Animal Behaviour quiz and come back to this page for any question you miss.