oviposition

Oviposition is the act of laying eggs by female animals. The term comes from Latin ovum, meaning egg, and positio, meaning placing. In many species, oviposition follows internal fertilization, though there are variations in the timing and mode of egg production across taxa. Oviposition is a life-history feature associated with oviparity, and it is contrasted with ovoviviparity and viviparity, in which development occurs inside the parent.

Oviposition behavior is diverse and widely distributed among the animal kingdom. Insects often use specialized structures called ovipositors to place eggs in specific substrates, such as plant tissues, soil, or water. Clutch size, egg size, and the location of deposition are tuned to ecological conditions and parental strategies. In many species, little or no parental care follows laying, while others show guarding or provisioning for eggs and early instars.

In birds and most reptiles, eggs are laid in nests or protected sites and typically incubated externally or by the parent. Eggs usually have shells that regulate gas exchange and moisture. Incubation duration and parental involvement vary; some species provide extensive warmth and protection, while others leave eggs unattended.

In fishes and amphibians, eggs are often laid in water or moist environments and may be externally fertilized or, in some cases, internally fertilized before deposition. Parental care ranges from none to highly specialized forms such as mouthbrooding or guarding eggs on substrates.

Monotremes, a small group of egg-laying mammals, include the platypus and echidnas. They lay eggs and incubate them outside the body, while milk is provided to the hatchlings through mammary secretions rather than nipples.

Ecological and evolutionary factors shaping oviposition include predation risk, resource availability, climate, and life-history trade-offs between egg production and parental investment.