A human who wants to store sperm to use it another day would need a trip to the cryogenic sperm bank, but a number of female animals can pull off the same feat without a deep freezer. It's a common strategy taken to different lengths by queen ants (30 years), snakes (seven years), chickens (30 days), and bats (six months), to name just a few. In comparison, human sperm survives in a woman's upper genital tract for a mere 3 to 5 days.

Crickets have one of the better-studied mechanisms of storage: A biomechanical trick in the female cricket's sperm storage organ somehow slows down sperm metabolism, extending their viability to several weeks. A study earlier this year found that sperm stored in female crickets have fewer free radicals, hydrogen-hungry molecules that cause cell damage. Free radicals are a normal byproduct of metabolism, but their accumulation may be a molecular cause for aging. By keeping sperm around for longer, a female can mate once, and then fertilize her eggs and give birth at her convenience.