QuestionAmerican crocodile
Do Crocodiles Care for Their Babies? Nesting and Hatchlings
Yes, crocodiles care for their babies, more than almost any other reptile. A mother guards her nest for two to three months, digs out the hatchlings when she hears them call, often carries them to the water in her jaws and protects them for weeks or months. Most other reptiles abandon their eggs once they are laid.
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How crocodiles build and guard their nests
Crocodilians, the group that includes crocodiles, alligators, caimans and gharials, all lay hard-shelled eggs on land. Females use one of two kinds of nest:
- Hole nests: the female digs a chamber in sand or soil, lays her eggs and covers them. The Nile crocodile, the gharial and many other crocodiles nest this way, usually in the dry season.
- Mound nests: the female scrapes together plants, sticks and mud into a heap. Rotting vegetation produces heat that keeps the eggs warm. Alligators, caimans and the saltwater crocodile use mounds, usually in the wet season.
The American crocodile is flexible and uses either, depending on the site. Clutch sizes range from about 10 to more than 80 eggs depending on the species and the size of the female.
Once the eggs are laid, the mother stays close. She often rests beside the nest or in the water nearby, and may eat little or nothing during the whole incubation period. She chases off predators such as monitor lizards, raccoons, mongooses and birds that try to dig up the eggs. Even so, predators destroy many nests when the mother is briefly away.
Nest temperature decides the sex of the babies
Crocodilians have no sex chromosomes. Instead, the temperature inside the nest during a key part of incubation decides whether each embryo becomes male or female, a system called temperature-dependent sex determination.
In many species the pattern is similar: nests at intermediate temperatures, roughly 31 to 33 °C (88 to 91 °F), produce mostly males, while cooler and hotter nests produce mostly females. Most natural nests contain a mix, because temperatures differ between the top and bottom of the egg pile. Scientists are studying how warming climates may shift the balance between the sexes in some populations.
Calls from inside the egg
Incubation usually lasts about two to three months. Near the end, the babies begin to make high-pitched calls from inside their eggs. Research on Nile crocodiles, published in 2008, showed that these calls work in two directions: they prompt the mother to start digging, and they spur other embryos in the same clutch to hatch at about the same time.
When she hears them, the mother opens the nest with her front feet and snout. Some hatchlings have trouble breaking free, and the mother may take an egg gently in her mouth and roll it between her tongue and palate to crack the shell. Crocodile jaws can bite with enormous force, yet mothers handle eggs and babies with great care.
Carrying babies to the water
Next comes the most famous behavior. The mother picks up the hatchlings, several at a time, and carries them in her mouth to the water. Her lower jaw has a pouch of skin that can hold a group of babies. She may make several trips until the whole clutch is safely in the shallows.
For centuries, people who saw this thought the crocodile was eating her young. In fact the mouth is the safest place for them during the short, dangerous trip from nest to water.
| Species | Incubation | Typical care after hatching |
|---|---|---|
| American crocodile | About 75–90 days | A few weeks, then young disperse |
| Nile crocodile | About 90 days | Weeks to several months |
| American alligator | About 60–70 days | Young stay in a pod near the mother for a year or more |
| Spectacled caiman | About 70–90 days | Young may gather in crèches guarded by one female |
How long do crocodile mothers protect their young?
After reaching the water, the babies stay together in a group, sometimes called a pod or crèche, near their mother. They hunt insects, small fish, crabs and frogs from the first days of life, so the mother does not feed them; her role is protection.
The young keep in contact with soft grunts and chirps. If one is grabbed or frightened, it gives a loud distress call, and the mother, and sometimes other adults including males, rush to defend it. The length of care varies by species. American crocodile young usually scatter after about a month, while young American alligators may stay near their mother for more than a year. In some caimans, several females leave their young together in one crèche watched over by a single adult.
Fathers are less involved, but not always absent. In some species, adult males stay near nests or young groups and will respond to hatchlings in distress.
Why care matters: survival of young crocodiles
Despite all this effort, most baby crocodiles do not survive. Nests are raided by predators or flooded by rising water. Hatchlings are only 25 to 35 cm (10 to 14 in) long and are eaten by herons, storks, eagles, large fish, snakes, monitor lizards, mammals and larger crocodiles. Only a small percentage of the eggs laid in a typical season produce an adult.
Parental care improves those odds during the riskiest weeks of life. Combined with large clutches and long adult lives, often several decades, it allows crocodile populations to persist even though few babies make it.
Crocodiles and their bird relatives
Crocodilians’ closest living relatives are birds, not lizards or snakes. Both groups descend from a shared ancestor among the archosaurs, the group that also includes dinosaurs. Nest guarding, calling between parents and young, and parental care of hatchlings are found in both crocodilians and birds, and fossil nests suggest that many dinosaurs cared for their young too. The gharial of India and other crocodilians show that this caring behavior is ancient.
Frequently asked questions
Do crocodiles eat their babies?
Mothers do not normally eat their own young. When people saw a crocodile with hatchlings in her mouth, they long assumed she was eating them, but she is actually carrying them safely to the water. Young crocodiles are, however, sometimes eaten by other, unrelated adult crocodiles.
How long do baby crocodiles stay with their mother?
It varies by species. Young American crocodiles usually disperse after a few weeks, Nile crocodile young may stay near their mother for weeks to several months, and young American alligators often remain in a group near the mother for a year or more.
Do male crocodiles help raise the young?
Mostly the mother does the work, but males of some species stay near the nest or young, and both male and female adults will respond to the distress calls of hatchlings. The amount of help from males varies a lot between species and individuals.
How many baby crocodiles survive?
Very few. Many nests are dug up by predators or flooded, and hatchlings are eaten by birds, fish, mammals, monitor lizards and other crocodiles. Only a small percentage of eggs laid ever produce an adult crocodile.
How do crocodile mothers know when to open the nest?
The babies call from inside their eggs shortly before hatching. These high-pitched calls tell the mother to dig open the nest and also seem to help the brothers and sisters hatch at the same time.
Is a crocodile a boy or a girl?
In crocodiles the sex is not set by chromosomes but by the temperature of the nest during incubation. In many species, middle temperatures produce mostly males, while cooler and hotter nests produce mostly females.
Sources and further reading
- Vergne, A. L. & Mathevon, N., "Crocodile egg sounds signal hatching time", Current Biology (2008)
- IUCN Red List of Threatened Species, "Crocodylus niloticus"
- Encyclopaedia Britannica, "Crocodile"
Cite this page
“Do Crocodiles Care for Their Babies? Nesting and Hatchlings.” Animal Atlas, https://animals.bigworldlist.com/questions/do-crocodiles-care-for-their-babies/.
