What is sperm competition among animals?

Sperm competition is a form of mating competition that occurs in sexual species when a female accepts multiple mating partners within a relatively short timeframe. Because the sperm from different males may overlap within the female’s reproductive tract, males have evolved various behavioral adaptations to maximize their paternity and ensure their sperm supersedes that of their competitors.12

These strategies often include:

• Mate-guarding: Males remain near a female after mating to prevent other males from copulating with her before she lays her eggs, such as the behavior seen in the cobalt milkweed beetle or acorn woodpeckers.1
• Sperm removal or displacement: Some species, such as damselflies and dragonflies, use their genitalia to physically remove or compact the sperm of previous mates. Similarly, male dunnocks may stimulate a female to eject sperm from prior matings.1
• Nuptial gifts: Males may provide food or other resources to females to increase their paternity, as the size of these donations often correlates with the amount of sperm transferred.12