CROCODILE BEHAVIOR: COMMUNICATION, FEEDING, MATING

CROCODILE BEHAVIOR

crocodiles like to sun themselves on mud banks

Crocodiles are considered to be more advanced than other reptiles mentally and socially as well as physically. They learn things faster than other reptiles and are the only reptiles capable of producing loud sounds. Dr. Daphne Soares, a neuroscientist at the University of Maryland, told the New York Times, “They get a bad rap for being stupid little reptiles. But they're very curious, very alert, and they want to know what's going on."

Danny Goodisman wrote in Animal Diversity Web: Crocodilians are poikilothermic (cold-blooded), and can only regulate their internal body temperature by arranging for their environment to warm them. Temperate species will bask in the sun during the day to raise their body temperature, returning to the water to cool off; they mostly hunt at night, leaving the daytime for basking in the sun. Opening their mouths can also cool them off, since the large exposed wet surface allows much evaporation. Tropical species may avoid the hot sun by remaining under water or mud during the day. Some crocodilians also estivate (sleep out the summer). Alligators, which live in temperate regions, may remain completely submerged except for their nostrils when the air is very cold in the winter. After feeding, crocodilians tend to seek more heat, as it speeds digestion. [Source: Danny Goodisman, Animal Diversity Web (ADW), September 9, 2002]

Crocodilians are capable of staying underwater for long periods of time. They usually submerge for 10-15 minutes, but can stay submerged for as long as two hours to avoid a perceived threat. This is accomplished by slowing down their metabolism and reducing oxygen consumption. [Source: Katie Foster, Animal Diversity Web (ADW) /=]

All crocodilians possess integumentary sense organs located in the skin and covering much of the animal’s body including the body, tail, cloaca and inner surfaces of the legs, as well as on the head and jaws. These are likely used to detect changes in pressure caused by touch or the movement of prey in water; this sense is likely used for hunting in murky water.

Crocodiles swallow rocks. No one knows why they do this. It is believed to be related to their ancestry with birds (some birds and other animals too swallow pebbles to aid their digestion). Studies have shown that crocodiles swallow stones equivalent to one percent of their body weight no matter how big they are. In one study, a growing crocodile with only big rocks present would swallow some big stones and regurgitate some smaller one to get the body weight just right.

Crocodile Movement, Swimming and Speed

It is said crocodiles can run at speeds up to 40 kilometers per hour (25 mph) for short bursts. More likely it is closer 16 kilometers per hour (10 mph). Crocodile expert Rob Bredl told National Geographic, "It's a myth that they can run as fast as a horse. They are big creatures with little short legs. But they can strike with amazing speed. In the water however crocodiles can surge forward short bursts at up to 50mph by tucking their front and rear legs in and thrusting with their powerful tails.” Some species can leap off the ground and stand on their hind legs to get at meat hung from a pole. Their tails are strong enough to dislocate a person’s jaw with a single whack.

The normal crocodile gait is with their bodies off the ground. Their ankles swivel to allow their legs to be almost underneath their body, making their gait resemble that of a mammal. No other reptile moves in this way. Crocodilians run by simply speeding up their walk. In smaller crocodilians this may change into a "gallop" in which it appears the crocodile is be bouncing. Crocodilians can also move like lizards, moving one foot at a time with their bellies scraping on the ground. They use this mode of movement when sliding down a river bank when frightened and sometimes occurs when they are running and their legs get out of sync. [Source: Danny Goodisman, Animal Diversity Web (ADW), September 9, 2002]

Crocodiles swim with back-and-forth movements of their tail. Most of the time crocodilians cruise slowly through the water, holding their legs against their body to reduce drag. They are also capable of great bursts of speed, including a "tail walk" like dolphins do, in which their head and body are held vertically out of the water. /=\

Crocodile Social Behavior

Crocodile adults are territorial (defend an area within the home range), and mark their territory by loudly slapping their head down on the water or snapping their jaws on the surface of the water. Male crocodiles are particularly territorial and status conscious. They establish a hierarchy that allows them live in crowded conditions and avoid battles. One scientist told the New York Times, “Crocodiles known their neighbors for miles around, and they know who’s who, who’s inferior, who’s superior.” This helps them live to ripe old ages.

According to Animal Diversity Web: Crocodilians are normally solitary animals, but plentiful food may bring many individuals together. Some species have been observed to hunt cooperatively. Even when large numbers congregate, they do not seem to fight over food. When large prey is caught, another crocodile may help to dismember it, so that the pieces are small enough to eat. [Source: Danny Goodisman, Animal Diversity Web (ADW), September 9, 2002]

Dominant animals tend to swim higher in the water; other crocodilians of the same species communicate their submission by swimming lower in the water. Dominant animals control access to mates, choice nesting sites, food, basking sites, and living space. During drought, territories are forgotten as crocodilians crowd into the smaller remaining inhabitable area, although hierarchies are still observed. In some species and in some areas, territories are only maintained by males or only during mating season.

Combat between crocodilians is rare, but does sometimes occur between animals of the same size competing for dominance. The two combatants line up next to each other facing opposite directions and bang the sides of their heads together; they also sometimes bite each other, but in either case they rarely cause any lasting damage. /=\

Crocodile Communication

Crocodiles communicate with vision, sound and chemicals usually detected by smelling. They also employ pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species). Among the sounds used in communication are hisses, grunts, chirps, burps, growls and infrasonic sounds. Physical displays include head slapping, body arching and bubble blowing.

Natalie Angier wrote in the New York Times, Crocodilians “will engage in sophisticated behavior that leaves most reptiles in the cold. They vocalize to each other. They squabble over status and can distinguish between friendly hominid and annoying graduate student with dart gun. In caring for their young, they outcluck a mother hen, for what hen can protect her babies by carrying them in her jaw? "They're not like big lizards," said Dr. George Amato, a geneticist at the Wildlife Conservation Society, a division of the Bronx Zoo. "It's clear when you spend time with them that they are quite complex." [Source: Natalie Angier, New York Times, October 26, 2004]

According to Animal Diversity Web: Crocodilians communicate with each other by means of sounds, postures, motions, odors released by four scent glands, and by touch. They also communicate by slowly lifting their jaws off the ground with their mouth closed. Vocal sounds are made by forcing air through a voice box (larynx) in the throat. Young call to adults when in danger, but also are very vocal while being fed. Sounds (by the hatchlings themselves or by adults) also seem to keep young together. Adults also produce sounds to communicate with other adults. The most common adult sound is a loud, low roar which is repeated, and may be echoed by other adults. During mating, softer "purrs" are made. Threatened crocodilians may growl. Adults also grunt to signal to juveniles they will help, and may hiss while defending juveniles. [Source: Danny Goodisman, Animal Diversity Web (ADW), September 9, 2002]

It is generally true that crocodilians' skin color can change depending on the environment or the crocodile's mood. Additionally, when the jaw is gaping, bright yellow or orange tongue colors may appear as social or warning signs. Crocodilians can achieve complex vocalizations by forcing exhaled air through a constriction by varying tensions in the muscles lining the glottis, and by expanding the throat via the hyoid apparatus, amplification can be achieved. It is thought that chemical detection is achieved on land when sensory epithelial cells detect chemicals as air passes through the sinuses and achieved in the water by the chemoreceptors lining the tongue. Communication has also been shown to involve pheromones secreted from the chin and paracloacal musk glands. Dome pressure receptors (DPRs) located on head scales, particularly around the jaws, and integumentary sense organs (ISOs), located on the caudal margin of body scales, rapidly alert the crocodile to potential prey by detecting pressure waves created by disturbances of the water surface. Crocodilians can detect frequencies ranging from below 10 Hz to over 10 kHz and, within particular bandwidths, sound pressure levels below -60 dB can be detected. [Source: Jamison Law, Animal Diversity Web (ADW) /=]

Crocodiles on the Hunt

Crocodiles spend most of their time doing nothing. Rather than pursue prey they are opportunists, who lurk in shallow, murky tea-colored water waiting for fish or turtle to come floating their way or for some land animal to come within striking distance of the shore. Dangling arms and legs can attract crocodiles. Sometimes they bite paddles.

crocodile attacking a tiger

Danny Goodisman wrote in Animal Diversity Web: Crocodilians hunt by lying concealed until some prey comes close to them. They are capable of very short bursts of high speed to catch prey, but cannot maintain speed to give chase if the initial attack is unsuccessful. These extreme bursts of speed also produce large amounts of lactic acid, which crocodilians are inefficient at removing; after an attack, they must rest to clean out their blood and replenish their oxygen supply. [Source: Danny Goodisman, Animal Diversity Web (ADW), September 9, 2002]

Crocodiles that attack animals usually wait for the animals to come to drink and grab their victim by the leg or sometimes by the snout and pull it into the water. To avoid encounters with crocodiles many animals prefer to drink from tributary springs rather than rivers deep enough to support crocodiles.

Crocodiles can scull very quietly through the water with their tails. They can approach river banks with barely ripple to give away their presence. Wildlife photographer Mark Deeble said that usually crocodiles “lie silent and submerged in water, only their eyes, nostrils and ears breaking the surface. When an animal comes...their eyes vanish from the water with a ripple. Then suddenly they burst from the water in a splashing furry and lunge, jaws open, for their prey."

Some crocodilians employ a technique called "sweeping" to catch fish in which they move their head back and forth, sideways — in slow motion with their mouth open — while underwater, hoping to bump into prey....and if they do, they slam their jaws lightning fast to catch it. [Source: Isabell Rivera, PetHelpful, October 4, 2023]

Crocodile Attack Zone

The attack zone of a large crocodile is about a two meter semicircle in front of the attacking reptile. This is the distance that a crocodile can lunge and seize its prey. Beyond two meters is out of the croc’s range. During an attack a crocodile uses: 1) its powerful legs to push itself upwards; 2) its powerful tail to surge forward; and its powerful jaws to grasp the prey.

Even though crocodiles have big teeth they generally don't kill their victims by biting them. Rather they clamp onto their prey with their powerful vice-like jaws and pull them underwater. Victim usually die from drowning. In some cases the crocodile performs a “death roll” and twists the body of their victims enough to break their necks. If an animal is too large to drown the crocodile may kill it by eating out its intestines, heart and liver. When it eats it twists off chunks of meat.

Although crocodiles are extremely powerful animals they tire easily. Unless they quickly drown their victims, fights can drag on for over an hour, with the crocodile spending most of its time clamped on to their victim, just sitting there and resting until it can resume the fight. Their palatal valve can be used to seal off the throat so a crocodile can bite underwater without getting water into its lungs or stomach.

The only animals that present a real danger to crocodiles are humans and other crocodiles. Few animals attack full grown crocodiles. Their nests however are vulnerable to pilfering mongooses, vultures, monitor lizards and other predators. Young crocodiles are sometimes taken by large birds such as eagles and herons. Mother crocodiles have to be particularly watchful for six foot tall goliath herons. Adult males often eat baby crocodiles, so will females when presses. Mothers will even eat their own young so that she and other members of her brood can survive.

Feeding Crocodile

Crocodiles tend to hunt rough fish undesirable for human consumption. They eat relatively infrequently. Often many days pass between meals Like other large cold-blooded animals with slow metabolism crocodiles can survive long periods — up to two years — without eating.

Crocodiles can only grip and rip with their massive jaws, they can not chew. Their teeth are designed for grasping and holding prey rather than cutting off pieces of meat. To break off a hunk of meat from large prey a crocodile grabs a hold of the carcass and twists its body around like a child rolling down a hill. Pieces as large as a goat head can be swallowed whole and large chunks of meat are beaten against the surface of the water to break them into smaller pieces and soften them up. With smaller prey crocodiles often move their heads from side to side when. This allows them to slam their jaws and expel water without also losing fish in their mouth.

According to Animal Diversity Web: All crocodilians have strong jaw muscles for biting and holding prey. They are all entirely carnivorous. Prey is not chewed or ground in the mouth: once it is impaled on the sharp teeth, it is swallowed whole. Crocodilians need not feed often. A study on Nile crocodiles indicated that they usually eat only about 50 full meals a year. While their staple food is always fish, large crocodilians may eat mammals; smaller ones' diet may include insects, tadpoles, frogs, snails, crabs, shrimps, birds and small fishes. Snakes, molluscs, turtles and bats may also be eaten. Crocodilians are opportunistic hunters; they eat whatever they can catch if they are hungry. Flying prey can be caught by the crocodilians leaping into the air with thrusts of their powerful tail. Some larger crocodilians may also eat humans. [Source: Danny Goodisman, Animal Diversity Web (ADW), September 9, 2002]

Crocodile can only digest a relatively small amount of food. Their stomachs are relatively small and need time break down large gulped down hunks of meat with acids secreted by the stomach powerful enough to dissolve bones and cartilage. Large carcasses are stashed away and eaten little by little. Crocodiles have few competitors so they can store their kills and eat over several days. Food is stored as fat in the animals' tails, backs, and elsewhere in the body; up to 60 percent of the food intake may be converted to fat. This, the fact that they're poikilothermic (cold blooded), and crocodilians' opportunistic hunting strategy allow crocodilians to survive for long periods with no food at all: large crocodilians may be able to survive up to two years between meals. /=\

Male Crocodiles

River colonies of crocodiles are often ruled by massive dominant males that, among other things, control which crocodiles bask where on sand bars in the middle of the river. Sometimes these males slap their head on the water express territoriality and small males stupid enough to intrude are attacked and sometimes killed and eaten. To avoid trouble small males that pass near the large male's territory must lift up their head and expose their throat, an act of submission.

Large males sometimes slap their head on the water to express territoriality. Small intruders are attacked and sometimes killed and eaten. Aggressive males sometimes take bites out of other adult crocodiles. Some males lose all their teeth in fights with other males.

Natalie Angier wrote in the New York Times, “For their part, male crocodiles are as territorial and status-conscious as are male birds, and they establish hierarchies that allow them to live in often crowded conditions without needing to risk their lives repeatedly in battle. Their aversion to potentially lethal acts of showmanship, coupled with the many hours they spend in the crocodilian zen of vigilant stillness, allows them to live for half a century or longer. Crocodiles don't like to make waves, though when they're hungry, they sure like to feel them. [Source: Natalie Angier, New York Times, October 26, 2004]

Crocodile Mating

crocodile mud track

During the mating season a male crocodile rubs his body against the female. Crocodiles have numerous touch receptors around their heads which are used in elaborate touching and stroking during mating. Before copulation he positions himself on top of the female by biting into the females necks and wrapping his legs around hers. Sex usually last for only around three minutes. Sex often takes place on a shallow mudbank. When it takes place in the water the female is often completely submerged.

Polygyny (males mate with more than one female) has been observed in all species studied. Describing the water dance of male crocodile, Diane Ackerman wrote in “A Natural History of the Senses “: "Stretching its enormous head out of the water, it puffs up its throat , tenses like a body builder, and a rolling thunder-buster bellow splits the air, and the water sizzles all around its body, raining upwards like frying diamonds. We see the water dance, but other [crocodiles] hear its infrasonic signal, made only by other males, perhaps as a courtship display or perhaps also as a full-body raspberry directed at other males." [Source: Diane Ackerman, A Natural History of the Senses, Vintage Books, 1990]

Danny Goodisman wrote in Animal Diversity Web: Sexual maturity is reached once crocodilians reach a certain age and size (both are important: a crocodilian not big enough to become sexually mature may not, even if it is old enough). Crocodilians' sex is determined by the temperature of the environment at a critical stage in development; there is no X or Y chromosome, like birds and mammals have. Crocodilians continue to grow their entire lives, even after sexual maturity has been reached. [Source: Danny Goodisman, Animal Diversity Web (ADW), September 9, 2002]

Crocodile Eggs and Nests

Crocodiles lay their eggs in nests made out of decaying plant material and/or mud. The nests may dry so hard that hatchlings would be trapped inside without help. Adults, especially mothers, often guard nests. If the eggs get dry the mother urinates on them.

Female crocodiles usually lay between 40 and 80 brittle eggs. After they have been deposited in a small hole that the mother digs with her hind legs the eggs are covered with dirt. The eggs usually hatch about two or three months later. All eggs in a nest hatch at the same time, and the entire brood leaves the nest at once.

Unlike most reptiles, crocodiles stay with their eggs until they are hatched and viciously defend them. Often times the mother doesn't move from the nest the entire time — not even to eat — and growls at anything that comes within a hundred yards of the nest. One scientist observed a female who only ate once during the entire three month period.

Few animals attack full grown crocodiles, but nests are vulnerable to pilfering mongooses, vultures, monitor lizards and other predators. Young crocodiles are sometimes taken by large birds such as eagles and herons. The six foot tall goliath heron can be especially deadly.

Crocodile Parenting and Young

20080318-Chinese alligator adult chinese alligator fund2.gif
Mother Chinese alligator
and young When the hatchlings emerge they cheep like chicks, The mother responded by uncovering the nest and carrying the newborns to the water. When the first hatchling chirp the mother digs up the nest, and both the male and female watch over the young crocodiles for the first two months of their life, while they learn to hunt frogs and insects.

An adult female crocodile picks up her young with her teeth and carries them young around in a pouch at the bottom of her mouth. The pouch forms only after she hears the chirping of her babies. Some negligent mothers fail to react when the baby crocodiles start to hatch, and the young either suffocate or the eggs rot.

Mothers may stay with their young for a couple of years, protecting them from predators and helping them find food when food is scarce. Some crocodiles have been observed leading their young to food sources by vocalization exchanges. Adults respond aggressively to hatchlings' distress cries, and mothers (and fathers, in some species) may attend hatchlings for several weeks. Crocodilians from the same brood stay together at least while they are young; in some species family groups stay together much longer. [Source: Danny Goodisman, Animal Diversity Web (ADW), September 9, 2002]

'Virgin Birth' Recorded in a Crocodile for the First Time

In June 2023, scientists announced the first ever recorded case of a crocodile "virgin birth" after a female that had been isolated for 16 years was discovered with a clutch of eggs. An American crocodile (Crocodylus acutus) was taken into captivity in 2002 when she was two years old and placed in an enclosure at Parque Reptilandia in Costa Rica. She remained alone for the next 16 years. But in January 2018, a clutch of 14 eggs was found in the enclosure. The discovery provides "tantalizing insights" into the evolutionary origins of the trait, potentially shedding light on the reproductive capabilities of dinosaurs, a new study finds. [Source: Hannah Osborne, Live Science, June 7, 2023]

Live Science reported: Virgin births, also known as facultative parthenogenesis (FP), is a type of asexual reproduction in species that would normally reproduce sexually. Scientists have documented it in birds, sharks, lizards and snakes in captivity, among other species. Until now, it had never been recorded among Crocodilia. In a study published on June 7, 2023 in the journal Biology Letters, researchers said seven of the 14 eggs produced by the crocodile in Costa Rica were viable. Zoo caretakers incubated these eggs, but they didn't hatch, so after three months, they opened the eggs. The contents of six of the eggs was "not discernable," but one contained a fully-formed, but non-viable fetus. Genetic analysis showed it was almost identical to the mother.

The team, led by Warren Booth, an entomologist at Virginia Tech, wrote in the study that it was "disappointing" the egg failed to hatch, but that it is not unusual for offspring born this way to suffer abnormalities and fail to thrive. FP, they added, may be more common in species on the brink of extinction, and studies investigating wild populations could reveal more cases. They also said the discovery of a virgin birth in a crocodile means FP has now been found in both birds, which descended from dinosaurs, and a crocodilian, suggesting a common evolutionary origin. Birds and crocodilians are the remaining representatives of archosaurs — the group that also included dinosaurs and pterosaurs. "This new evidence offers tantalizing insights into the possible reproductive capabilities of extinct archosaurian relatives of crocodilians, notably the Pterosauria and Dinosauria," they wrote.

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, CNN, BBC, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated February 2025