Animals That Lay Eggs

Egg-laying at a glance

Compare the group, its examples and the exceptions. Scroll the table sideways on a small screen.

Animals That Lay Eggs

1. 1

   Birds

   Eggs develop outside the mother

   All living bird species reproduce by laying eggs. A chicken is a familiar example, but nest construction, incubation and the development of hatchlings differ greatly among birds. An unfertilised egg is not a developing chick.

2. 2

   Platypus

   Egg-laying mammal

   The platypus is a monotreme. It lays eggs in a burrow and feeds the hatched young with milk. Egg-laying does not make it a reptile: classification depends on evolutionary relationships and a wider set of traits.

3. 3

   Short-beaked echidna

   An egg carried in a temporary pouch

   The female short-beaked echidna lays an egg into a pouch. The very young hatchling continues developing there. Echidnas and the platypus are the living monotremes; they should not be described as just two species worldwide.

4. 4

   Sea turtles

   Eggs buried on land

   Sea turtles come ashore to nest even though they spend much of their lives at sea. Nest temperature influences sex determination. Clutch size and timing vary by species and site; one number cannot describe every nest.

5. 5

   Crocodilians

   Eggs in a nest

   Crocodilians lay eggs rather than give live birth. Nesting, incubation and parental behaviour are part of the species’ biology. Their egg-laying does not mean every other reptile follows the same reproductive strategy.

6. 6

   Egg-laying snakes

   Some snakes lay; others give birth

   An egg-laying snake deposits eggs that develop outside its body. Live-bearing snakes retain developing young. Identify the species before predicting whether a snake produces a clutch or a litter; broad family names can conceal exceptions.

7. 7

   Egg-laying lizards

   Reproduction varies within lizards

   Many lizards lay eggs, while other species produce live young. Even a familiar group name such as gecko or skink is not enough to determine a species’ exact reproductive biology.

8. 8

   Frogs

   Eggs need suitable conditions

   Many frogs lay eggs in water or moist places, but not every egg becomes a free-swimming tadpole. New Zealand’s native frog accounts include development into froglets within the egg. Egg-laying and having an aquatic larval stage are separate questions.

9. 9

   Bony fishes

   Many species lay eggs

   Salmon provide an egg-laying example, while live-bearing fishes show why “all fish lay eggs” is misleading. Fertilisation, nesting, parental care and the form of the hatchling differ between species.

10. 10

    Egg-laying sharks

    Embryos develop in egg cases

    Some sharks lay egg cases, while other sharks give live birth. The Florida Museum distinguishes egg-laying from several kinds of live-bearing development. A “mermaid’s purse” is an egg case, not proof that every shark species lays one.

11. 11

    Egg-laying insects

    Common, but not universal

    Bees and butterflies are familiar egg-laying insects. Tsetse flies are a clear exception to the old claim that all insects lay eggs: the female nourishes a larva internally and gives birth to it. A larva is a life stage, not a separate animal group.

12. 12

    Octopuses

    Eggs with species-specific care

    Many familiar octopuses attach eggs to a sheltered surface and tend the brood. The place of development, clutch and care strategy need the exact species; avoid assigning one species’ reproductive timetable to every octopus.

What do oviparous, viviparous and ovoviviparous mean?

Oviparous means egg-laying: an egg is deposited and the embryo develops outside the mother’s body. Viviparous means live-bearing. These descriptions concern where development takes place and how young are born, not whether an animal is a mammal, a reptile or a fish.

Ovoviviparous is an older term for retaining eggs internally while embryos rely on yolk and the young are born alive. Terminology varies between animal groups. The Florida Museum explains that shark literature often uses aplacental viviparity instead. A live-born animal is not necessarily nourished by a placenta like a human embryo.

Why are platypuses and echidnas still mammals?

Egg-laying is one trait, not a complete classification. Monotremes have mammalian features including hair and milk production. Their hatchlings depend on milk after leaving the egg, so the egg is only the first part of the reproductive story.

The Australian Museum distinguishes the platypus from the short-beaked echidna in Australia and the long-beaked echidnas of New Guinea. “Platypus and echidna” describes the familiar forms, not a two-species global total. For identification, use the exact animal name and location.

Do all insects lay eggs?

No. Tsetse flies demonstrate why that universal statement is wrong. A female produces a developed larva rather than depositing an egg that develops outside her body. WHO’s description of the tsetse life cycle documents this reproductive mode.

The same caution applies when learning from a bee, butterfly or beetle. An example can explain one life cycle without representing every member of the class Insecta. Ask separately whether eggs are laid, what hatches or is born, and which developmental stages follow.

Does every egg need a nest, a shell or a tadpole stage?

A bird’s nest can make egg development easy to imagine, but an animal egg does not have to resemble a chicken egg. Egg cases, jelly-coated eggs and buried nests are different structures. A habitat must provide appropriate conditions for the species; a suitable place for one animal’s eggs may be unsuitable for another’s.

Hatching also does not mean the same thing in every life cycle. New Zealand’s Department of Conservation explains that some native frogs develop into nearly formed frogs inside their eggs. That differs from the familiar pond-spawn-and-tadpole sequence. Both can involve egg-laying.

Does temperature decide whether hatchlings are male or female?

It does in some animals, including sea turtles, but it is not a rule for every egg-laying species or every reptile. NOAA explains the importance of incubation temperature for sea turtles. The stage of development and the species matter; do not treat a single temperature threshold as universal.

This is one reason conservation teams monitor nesting conditions carefully. It is not a reason for visitors to dig up, turn or move eggs. A nest may be protected and an intervention may harm development. Follow the local wildlife authority’s instructions and report a threatened nest rather than attempting an improvised relocation.

What should you do if you find wild eggs?

Observe without handling, keep pets away and avoid drawing a crowd to a nest. An unattended nest is not automatically abandoned. If eggs appear to be in immediate danger, contact a local wildlife authority or qualified rescue organisation and describe the location and what you can see.

Our animal identification collection can help you organise observations, but an egg photograph alone may not identify the species. Record the setting without disturbing it. Do not take eggs home to hatch them or buy wild eggs as a rescue gesture.