Skip to main content

Animal lists · 12 entries

Animals That Lay Eggs

Oviparous animals — including all birds, most reptiles, monotremes, most fish and all insects — reproduce by laying eggs rather than giving live birth, ranked here by group with notes on exceptions such as viviparous snakes and ovoviviparous sharks.

Updated 25 July 2026

Egg-laying is the ancestral reproductive mode for vertebrates and remains the dominant strategy across most animal groups. But live birth has evolved independently many times — in snakes, sharks, lizards and mammals — so "animals that lay eggs" is not a clean category without exceptions.

This list covers the major oviparous groups and notes well-known exceptions within each. Monotremes — platypus and echidna — are the only egg-laying mammals. Most mammals give live birth.

How this list was compiled

Entries are major animal groups or representative species that reproduce primarily by laying eggs (oviparity). Viviparous (live-bearing) and ovoviviparous (egg retained internally until hatching) exceptions within each group are noted. Live-bearing mammals other than monotremes are excluded from the primary list. Egg type — hard-shelled, leathery, gelatinous — is noted where relevant.

Animals That Lay Eggs

  1. Birds (all species)

    Hard-shelled eggs; all oviparous

    Every bird species lays eggs. No exceptions. Incubation method and nest type vary enormously.

  2. Platypus

    Leathery egg; monotreme

    One of two monotreme genera. Lays one to three eggs in a burrow and nurses young with milk from skin patches.

  3. Echidna

    Leathery egg; monotreme

    Lays a single egg into a pouch. Young hatch at roughly 1.5 cm and remain in the pouch for weeks.

  4. Sea turtle

    Leathery eggs; beach nesting

    Females return to natal beaches to lay clutches of 50–200 eggs in sand. Temperature determines sex in most species.

  5. Crocodile

    Hard-shelled; nest mound or hole

    Female guards nest and assists hatchlings to water. Temperature-dependent sex determination.

  6. Most snakes

    Oviparous (most); viviparous exceptions

    Most lay eggs, but boas, vipers and some sea snakes give live birth — ovoviviparity evolved independently multiple times.

  7. Most lizards

    Oviparous (most); viviparous exceptions

    Skinks and geckos include many live-bearing species. Oviparity remains the default for the group.

  8. Frog

    Gelatinous eggs; no shell

    Most lay eggs in water or moist environments. No calcified shell — gelatinous mass protects embryos.

  9. Most fish

    Oviparous (most); live-bearing exceptions

    Sharks, guppies and some others give live birth. The majority of fish species lay eggs.

  10. Insects (all species)

    Eggs; enormous variety

    All insects lay eggs. Form ranges from microscopic to several centimetres. Metamorphosis follows in most groups.

  11. Octopus

    Gelatinous strings; guarded brood

    Female attaches egg strings to rocks and guards them without feeding until they hatch — then typically dies.

  12. Chicken

    Hard-shelled; daily laying

    Domestic chickens lay unfertilised eggs regularly. Wild junglefowl ancestors laid seasonally in clutches.

Key facts

  • All birds lay eggs without exception — no bird species gives live birth.
  • Monotremes — platypus and echidna — are the only egg-laying mammals.
  • Live birth has evolved independently in snakes, lizards, sharks and most mammals — oviparity is ancestral but not universal.
  • Reptile egg type varies — hard-shelled in crocodiles, leathery in turtles, soft in most lizards and snakes.
  • Temperature during incubation determines sex in crocodiles, turtles and many lizards — not genetics.
  • Insects all lay eggs, representing the largest number of oviparous species on Earth.

Animals That Lay Eggs: frequently asked questions

Which animals lay eggs?
Birds, reptiles, monotremes, most fish, all insects, octopuses and many other invertebrates. Live-bearing exceptions exist in snakes, lizards, sharks and all other mammals.
Do mammals lay eggs?
Only monotremes — the platypus and echidna. All other mammals give live birth.
Do snakes lay eggs?
Most do, but boas, vipers and some sea snakes give live birth. Live birth has evolved independently in several snake families.
What is the difference between oviparous and viviparous?
Oviparous animals lay eggs that develop outside the body. Viviparous animals retain embryos internally and give live birth. Ovoviviparous animals retain eggs internally until they hatch.
Do all birds lay eggs?
Yes, without exception. No bird species gives live birth. Kiwi eggs are among the largest relative to body size.
Why did live birth evolve if egg-laying came first?
Live birth protects developing embryos from predation, desiccation and temperature fluctuation. It has evolved independently in at least 150 vertebrate lineages.

Sources

How we check facts: our sourcing standards →

More animal lists

All animal lists Animals A–Z
Donate