crocodilians | tropical-hobbies

Crocodilian teeth vary from blunt and dull to sharp and needle-like.[11] Broad-snouted species have teeth that vary in size, while those of slender-snouted species are more uniform. The teeth of crocodiles and gharials tend to be more visible than those of alligators and caimans when the jaws are closed.[40] The easiest way to distinguish crocodiles from alligators is by looking at their jaw line. The teeth on the lower jaw of an alligator fit into sockets in the upper jaw, so only the upper teeth are visible when the mouth is closed. The teeth on the lower jaw of a crocodile fit into grooves on the outside of the top jaw making both the upper and lower teeth visible when the mouth is closed.[41]

Crocodilians are polyphyodonts and able to replace each of their approximately 80 teeth up to 50 times in their 35 to 75-year lifespan.[42] They are the only non-mammalian vertebrates with tooth sockets.[43] Next to each full-grown tooth there is a small replacement tooth and an odontogenic stem cell in the dental lamina in standby, which can be activated when required.[44] Tooth replacement slows significantly and eventually stops as the animal grows old.[40]

Crocodilians

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Introduction :

What is crocodilian ?

From Wikipedia, the free encyclopedia

Crocodilia (or Crocodylia) is an order of mostly large, predatory, semiaquatic archosaurian reptiles, known as crocodilians. They first appeared 83.5 million years ago in the Late Cretaceous period (Campanian stage) and are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria. Members of the order's total group, the clade Pseudosuchia, appeared about 250 million years ago in the Early Triassic period, and diversified during the Mesozoic era. The order Crocodilia includes the true crocodiles (family Crocodylidae), the alligators and caimans (family Alligatoridae), and the gharial and false gharial (family Gavialidae). Although the term 'crocodiles' is sometimes used to refer to all of these, crocodilians is a less ambiguous vernacular term for members of this group.

Crocodilians .. introduction

Crocodiles as pet :

- Housing crocodiles : further reading & DIY projects

Zoo Exhabits and photos

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- Crocodiles Feeding

- Crocodiles Handling

-Crocodiles Health Care

- Crocodiles miscellaneous and other issues

- Species List : PART ONE -- PART TWO ( dwarf crocodiles )

Clockwise from top-left: saltwater crocodile(Crocodylus porosus), American alligator (Alligator mississippiensis), and gharial (Gavialis gangeticus)

Large, solidly built, lizard-like reptiles, crocodilians have long flattened snouts, laterally compressed tails, and eyes, ears, and nostrils at the top of the head. They swim well and can move on land in a "high walk" and a "low walk", while smaller species are even capable of galloping. Their skin is thick and covered in non-overlapping scales. They have conical, peg-like teeth and a powerful bite. They have a four-chambered heart and, somewhat like birds, a unidirectional looping system of airflow within the lungs, but like other non-avian reptiles they are ectotherms.

Crocodilians are found mainly in lowlands in the tropics, but alligators also live in the southeastern United States and the Yangtze River in China. They are largely carnivorous, the various species feeding on animals such as fish, crustaceans, molluscs, birds, and mammals; some species like the Indian gharial are specialised feeders, while others like the saltwater crocodile have generalised diets. Crocodilians are typically solitary and territorial, though cooperative feeding does occur. During breeding, dominant males try to monopolise available females. Females lay eggs in holes or in mounds and, unlike most other reptiles, care for their hatched young.

Eight species of crocodilians are known to have attacked humans. The largest number of attacks comes from the Nile crocodile. Humans are the greatest threat to crocodilian populations through activities that include hunting and habitat destruction, but farming of crocodilians has greatly reduced unlawful trading in wild skins. Artistic and literary representations of crocodilians have appeared in human cultures around the world since at least Ancient Egypt. The earliest known mention of the story that crocodiles weep for their victims was in the 9th century; it was later spread by Sir John Mandeville in 1400 and then by William Shakespeare in the late 16th century and early 17th century.

Scientific classification

Kingdom:Animalia

Phylum:Chordata

Class:Reptilia

Clade:Eusuchia

Order:Crocodilia
Owen, 1842

Subgroups

†Borealosuchus
†Planocraniidae
Gavialoidea
Brevirostres
- Alligatoroidea
- Crocodyloidea

Crocodylia distribution

Mounted skeleton and taxidermy of Nile crocodile

Crocodilians, like this spectacled caiman, can hide in water with only their nostrils, eyes and ears at the surface.

Locomotion :

Crocodilians are excellent swimmers. During aquatic locomotion, the muscular tail undulates from side to side to drive the animal through the water while the limbs are held close to the body to reduce drag.[19][31] When the animal needs to stop, steer, or manoeuvre in a different direction, the limbs are splayed out.[19]Crocodilians generally cruise slowly on the surface or underwater with gentle sinuous movements of the tail, but when pursued or when chasing prey they can move rapidly.[32] Crocodilians are less well-adapted for moving on land, and are unusual among vertebrates in having two different means of terrestrial locomotion: the "high walk" and the "low walk".[13] Their ankle joints flex in a different way from those of other reptiles, a feature they share with some early archosaurs. One of the upper row of ankle bones, the astragalus, moves with the tibia and fibula. The other, the calcaneum, is functionally part of the foot, and has a socket into which a peg from the astragalus fits. The result is that the legs can be held almost vertically beneath the body when on land, and the foot can swivel during locomotion with a twisting movement at the ankle.[33]

Nile crocodile swimming. Sequence runs from right to left.

The high walk of crocodilians, with the belly and most of the tail being held off the ground, is unique among living reptiles. It somewhat resembles the walk of a mammal, with the same sequence of limb movements: left fore, right hind, right fore, left hind.[32] The low walk is similar to the high walk, but without the body being raised, and is quite different from the sprawling walk of salamanders and lizards. The animal can change from one walk to the other instantaneously, but the high walk is the usual means of locomotion on land. The animal may push its body up and use this form immediately, or may take one or two strides of low walk before raising the body higher. Unlike most other land vertebrates, when crocodilians increase their pace of travel they increase the speed at which the lower half of each limb (rather than the whole leg) swings forward; by this means, stride length increases while stride duration decreases.[34]

Crocodilians, like this American alligator, can "high walk" with the limbs held almost vertically, unlike other reptiles.

Though typically slow on land, crocodilians can produce brief bursts of speed, and some can run at 12 to 14 km/h (7.5 to 8.7 mph) for short distances.[35] A fast entry into water from a muddy bank can be effected by plunging to the ground, twisting the body from side to side and splaying out the limbs.[32] In some small species such as the freshwater crocodile, a running gait can progress to a bounding gallop. This involves the hind limbs launching the body forward and the fore limbs subsequently taking the weight. Next, the hind limbs swing forward as the spine flexes dorso-ventrally, and this sequence of movements is repeated.[36] During terrestrial locomotion, a crocodilian can keep its back and tail straight, since the scales are attached to the vertebrae by muscles.[14] Whether on land or in water, crocodilians can jump or leap by pressing their tails and hind limbs against the substrate and then launching themselves into the air.[19][37]

Jaws and teeth :

The snout shape of crocodilians varies between species. Crocodiles may have either broad or slender snouts, while alligators and caimans have mostly broad ones. Gharials have snouts that are extremely elongated. The muscles that close the jaws are much more massive and powerful than the ones that open them,[12] and a crocodilian's jaws can be held shut by a person fairly easily. Conversely, the jaws are extremely difficult to pry open.[38] The powerful closing muscles attach at the median of portion of the lower jaw and the jaw hinge attaches to the atlanto-occipital joint, allowing the animal to open its mouth fairly wide.[14]

Skull of American alligator

Crocodilians have some of the strongest bite forces in the animal kingdom. In a study published in 2003, an American alligator's bite force was measured at up to 2,125 lbf (9,450 N).[39] In a 2012 study, a saltwater crocodile's bite force was measured even higher, at 3,700 lbf (16,000 N). This study also found no correlation between bite force and snout shape. Nevertheless, the gharial's extremely slender jaws are relatively weak and built more for quick jaw closure. The bite force of Deinosuchus may have measured 23,000 lbf (100,000 N),[11] even greater than that of theropod dinosaurs like Tyrannosaurus.[39]

Skull of a Nile Crocodile(Crocodylus niloticus) compared to a human skull.

Skin and scales :

The skin of crocodilians is thick and cornified, and is clad in non-overlapping scales known as scutes, arranged in regular rows and patterns. These scales are continually being produced by cell division in the underlying layer of the epidermis, the stratum germinativum, and the surface of individual scutes sloughs off periodically. The outer surface of the scutes consists of the relatively rigid beta-keratin while the hinge region between the scutes contains only the more pliable alpha-keratin.[45]

Many of the scutes are strengthened by bony plates known as osteoderms, which are the same size and shape as the superficial scales but grow beneath them. They are most numerous on the back and neck of the animal and may form a protective armour. They often have prominent, lumpy ridges and are covered in hard-wearing beta-keratin.[12] Most of the skin on the head is fused to the skull.[14] The skin on the neck and flanks is loose, while that on the abdomen and underside of the tail is sheathed in large, flat square scutes arranged in neat rows.[12][46] The scutes contain blood vessels and may act to absorb or radiate heat during thermoregulation.[12]Research also suggests that alkaline ions released into the blood from the calcium and magnesium in these dermal bones act as a buffer during prolonged submersion when increasing levels of carbon dioxide would otherwise cause acidosis.[47]

Skin of a juvenile Nile crocodile

Some scutes contain a single pore known as an integumentary sense organ. Crocodiles and gharials have these on large parts of their bodies, while alligators and caimans only have them on the head. Their exact function is not fully understood, but it has been suggested that they may be mechanosensory organs.[48] Another possibility is that they may produce an oily secretion that prevents mud from adhering to the skin. There are prominent paired integumentary glands in skin folds on the throat, and others in the side walls of the cloaca. Various functions for these have been suggested. They may play a part in communication, as indirect evidence suggest that they secrete pheromones used in courtship or nesting.[12] The skin of crocodilians is tough and can withstand damage from conspecifics, and the immune system is effective enough to heal wounds within a few days.[49]

Thermoregulation

Crocodilians are ectotherms, producing relatively little heat internally and relying on external sources to raise their body temperatures. The sun's heat is the main means of warming for any crocodilian, while immersion in water may either raise its temperature by conduction, or cool the animal in hot weather. The main method for regulating its temperature is behavioural. For example, an alligator in temperate regions may start the day by basking in the sun on land. A bulky animal, it warms up slowly, but at some time later in the day it moves into the water, still exposing its dorsal surface to the sun. At night it remains submerged, and its temperature slowly falls. The basking period is extended in winter and reduced in summer. For crocodiles in the tropics, avoiding overheating is generally the main problem. They may bask briefly in the morning but then move into the shade, remaining there for the rest of the day, or submerge themselves in water to keep cool. Gaping with the mouth can provide cooling by evaporation from the mouth lining.[66] By these means, the temperature range of crocodilians is usually maintained between 25 and 35 °C (77 and 95 °F), and mainly stays in the range 30 to 33 °C (86 to 91 °F).[67]

Captive Indian gharial basking and gaping

The ranges of the American and Chinese alligator extend into regions that sometimes experience periods of frost in winter. Being ectothermic, the internal body temperature of crocodilians falls as the temperature drops, and they become sluggish. They may become more active on warm days, but do not usually feed at all during the winter. In cold weather, they remain submerged with their tails in deeper, less cold water and their nostrils just projecting through the surface. If ice forms on the water, they maintain ice-free breathing holes, and there have been occasions when their snouts have become frozen into the ice. Temperature sensing probes implanted in wild American alligators have found that their core body temperatures can descend to around 5 °C (41 °F), but as long as they remain able to breathe they show no ill effects when the weather warms up.[66]

Osmoregulation :

No living species of crocodilian can be considered truly marine; although the saltwater crocodile and the American crocodile are able to swim out to sea, their normal habitats are river mouths, estuaries, mangrove swamps, and hypersaline lakes, though several extinct species have had marine habitats, including the recently extinct "Gavialis" papuensis, which occurred in a fully marine habitat in the Solomon Islands coastlines.[68] All crocodilians need to maintain the concentration of salt in body fluids at suitable levels. Osmoregulation is related to the quantity of salts and water exchanged with the environment. Intake of water and salts takes place across the lining of the mouth, when water is drunk, incidentally while feeding, and when present in foods.[69] Water is lost from the body during breathing, and both salts and water are lost in the urine and faeces, through the skin, and via salt-excreting glands on the tongue, though these are only present in crocodiles and gharials.[70][71] The skin is a largely effective barrier to both water and ions. Gaping causes water loss by evaporation from the lining of the mouth, and on land, water is also lost through the skin.[70] Large animals are better able to maintain homeostasis at times of osmotic stress than smaller ones.[72] Newly hatched crocodilians are much less tolerant of exposure to salt water than are older juveniles, presumably because they have a higher surface-area-to-volume ratio.[70]

The kidneys and excretory system are much the same as in other reptiles, but crocodilians do not have a bladder. In fresh water, the osmolality (the concentration of solutes that contribute to a solution's osmotic pressure) in the plasma is much higher than it is in the surrounding water. The animals are well-hydrated, and the urine in the cloaca is abundant and dilute, nitrogen being excreted as ammonium bicarbonate.[72] Sodium loss is low and mainly takes place through the skin in freshwater conditions. In seawater, the opposite is true. The osmolality in the plasma is lower than the surrounding water, which is dehydrating for the animal. The cloacal urine is much more concentrated, white, and opaque, with the nitrogenous waste being mostly excreted as insoluble uric acid.[70][72]

Saltwater crocodile resting on beach

Distribution and habitat :

Crocodilians are amphibious reptiles, spending part of their time in water and part on land. The last surviving fully terrestrial genus, Mekosuchus, became extinct about 3000 years ago after humans had arrived on its Pacific islands, making the extinction possibly anthropogenic.[73] Typically they are creatures of the tropics; the main exceptions are the American and Chinese alligators, whose ranges extend as far north as the south-eastern United States and the Yangtze River, respectively. Florida, in the United States, is the only place that crocodiles and alligators live side by side.[74] Most crocodilians live in the lowlands, and few are found above 1,000 metres (3,300 ft), where the temperatures are typically about 5 °C (9 °F) lower than at the coast. None of them permanently reside in the sea, though some can venture into it, and several species can tolerate the brackish water of estuaries, mangrove swamps, and the extreme salinity of hypersaline lakes.[75] The saltwater crocodile has the widest distribution of any crocodilian, with a range extending from eastern India to New Guinea and northern Australia. Much of its success is due to its ability to swim out to sea and colonise new locations, but it is not restricted to the marine environment and spends much time in estuaries, rivers, and large lakes.[76]

Spectacled caiman immersed in vegetation covered water

Various types of aquatic habitats are used by different crocodilians. Some species are relatively more terrestrial and prefer swamps, ponds, and the edges of lakes, where they can bask in the sun and there is plenty of plant life supporting a diverse fauna. Others spend more time in the water and inhabit the lower stretches of rivers, mangrove swamps, and estuaries. These habitats also have a rich flora and provide plenty of food. The Asian gharials find the fish on which they feed in the pools and backwaters of swift rivers. South American dwarf caimans inhabit cool, fast-flowing streams, often near waterfalls, and other caimans live in warmer, turbid lakes and slow-moving rivers. The crocodiles are mainly river dwellers, and the Chinese alligator is found in slow-moving, turbid rivers flowing across China's floodplains. The American alligator is an adaptable species and inhabits swamps, rivers, or lakes with clear or turbid water.[75] Climatic factors also affect crocodilians' distribution locally. During the dry season, caimans can be restricted to deep pools in rivers for several months; in the rainy season, much of the savannah in the Venezuelan llanos is flooded, and they disperse widely across the plain.[77] Desert crocodiles in Mauritania have adapted to their arid environment by staying in caves or burrows in a state of aestivation during the driest periods. When it rains, the reptiles gather at gueltas.[78]

American crocodiles basking

Dry land is also important as it provides opportunities for basking, nesting, and escaping from temperature extremes. Gaping allows evaporation of moisture from the mouth lining and has a cooling effect, and several species make use of shallow burrows on land to keep cool. Wallowing in mud can also help prevent them from overheating.[79] Four species of crocodilians climb trees to bask in areas lacking a shoreline.[80] The type of vegetation bordering the rivers and lakes inhabited by crocodilians is mostly humid tropical forest, with mangrove swamps in estuarine areas. These forests are of great importance to the crocodilians, creating suitable microhabitats where they can flourish. The roots of the trees absorb water when it rains, releasing it back slowly into the environment. When the forests are cleared to make way for agriculture, rivers tend to silt up, the water runs off rapidly, the water courses can dry up in the dry season and flooding can occur in the wet season. Destruction of forest habitat is probably a greater threat to crocodilians than is hunting.[81]

Spacing :

Adult crocodilians are typically territorial and solitary. Individuals may defend basking spots, nesting sites, feeding areas, nurseries, and overwintering sites. Male saltwater crocodiles establish year-round territories that encompass several female nesting sites. Some species are occasionally gregarious, particularly during droughts, when several individuals gather at remaining water sites. Individuals of some species may share basking sites at certain times of the day.[19]

Feeding

Nile crocodile ambushing migratingwildebeest crossing the Mara River

Crocodilians are largely carnivorous, and the diets of different species can vary with snout shape and tooth sharpness. Species with sharp teeth and long slender snouts, like the Indian gharial and Australian freshwater crocodile, are specialised for feeding on fish, insects, and crustaceans, while extremely broad-snouted species with blunt teeth, like the Chinese alligator and broad-snouted caiman, specialise in eating hard-shelled molluscs. Species whose snouts and teeth are intermediate between these two forms, such as the saltwater crocodile and American alligator, have generalised diets and opportunistically feed on invertebrates, fish, amphibians, other reptiles, birds, and mammals.[11][82] Though mostly carnivorous, several species of crocodilian have been observed to consume fruit, and this may play a role in seed dispersal.[83]

In general, crocodilians are stalk-and-ambush predators,[11] though hunting strategies vary depending on the individual species and the prey being hunted.[19] Terrestrial prey is stalked from the water's edge and then grabbed and drowned.[19][84] Gharials and other fish-eating species sweep their jaws sideways to snap up prey, and these animals can leap out of the water to catch birds, bats, and leaping fish.[82] Small animals can be killed by whiplash as the predator shakes its head.[84] Caimans use their tails and bodies to herd fish into shallow water.[19] They may also dig for bottom-dwelling invertebrates,[13] and the smooth-fronted caiman will even hunt on land.[11]Some crocodilian species have been observed to use sticks and branches to lure nest-building birds.[85] Nile crocodiles are known to hunt cooperatively,[19] and several individuals may feed on the same carcass. Most species will eat anything suitable that comes within reach and are also opportunistic scavengers.[13]

A gharial eating a fish

Crocodilians are unable to chew and need to swallow food whole, so prey that is too large to swallow is torn into pieces. They may be unable to deal with a large animal with a thick hide, and may wait until it becomes putrid and comes apart more easily.[82] To tear a chunk of tissue from a large carcass, a crocodilian spins its body continuously while holding on with its jaws, a manoeuvre known as the "death roll".[86] During cooperative feeding, some individuals may hold on to the prey, while others perform the roll. The animals do not fight, and each retires with a piece of flesh and awaits its next feeding turn.[87] Food is typically consumed by crocodilians with their heads above water. The food is held with the tips of the jaws, tossed towards the back of the mouth by an upward jerk of the head and then gulped down.[84]Nile crocodiles may store carcasses underwater for later consumption.[13]

Reproduction and parenting

Crocodilians are generally polygynous, and individual males try to mate with as many females as they can.[88] Monogamous pairings have been recorded in American alligators.[89] Dominant male crocodilians patrol and defend territories which contain several females. Males of some species, like the American alligator, try to attract females with elaborate courtship displays. During courtship, crocodilian males and females may rub against each other, circle around, and perform swimming displays. Copulation typically occurs in the water. When a female is ready to mate, she arches her back while her head and tail submerge. The male rubs across the female's neck and then grasps her with his hindlimbs, placing his tail underneath hers so their cloacas align and his penis can be inserted. Mating can last up to 15 minutes, during which time the pair continuously submerge and surface.[88] While dominant males usually monopolise reproductive females, multiple paternity is known to exist in American alligators, where as many as three different males may sire offspring in a single clutch. Within a month of mating, the female crocodilian begins to make a nest.[19]

Mother American alligator with nest and young

Depending on the species, female crocodilians may construct either holes or mounds as nests,[19] the latter made from vegetation, litter, sand, or soil.[72] Nests are typically found near dens or caves. Those made by different females are sometimes close to each other, particularly in hole-nesting species. The number of eggs laid in a single clutch ranges from ten to fifty. Crocodilian eggs are protected by hard shells made of calcium carbonate. The incubation period is two to three months.[19] The temperature at which the eggs incubate determines the sex of the hatchlings. Constant nest temperatures above 32 °C (90 °F) produce more males, while those below 31 °C (88 °F) produce more females. However, sex in crocodilians may be determined in a short interval, and nests are subject to changes in temperature. Most natural nests produce hatchlings of both sexes, though single-sex clutches do occur.[72]

Nile crocodile eggs

The young may all hatch in a single night.[90] Crocodilians are unusual among reptiles in the amount of parental care provided after the young hatch.[19] The mother helps excavate hatchlings from the nest and carries them to water in her mouth. Newly hatched crocodilians gather together and stay close to their mother.[91] For spectacled caimans in the Venezuelan llanos, individual mothers are known to leave their young in the same nurseries, or crèches, and one of the mothers guards them.[92] Hatchlings of many species tend to bask in a group during the day and disperse at nightfall to feed.[90] The time it takes young crocodilians to reach independence can vary. For American alligators, groups of young associate with adults for one to two years, while juvenile saltwater and Nile crocodiles become independent in a few months.[19]

Growth and mortality :

Mortality is high for eggs and hatchlings, and nests face threats from floods, overheating, and predators.[19] Flooding is a major cause of failure of crocodilians to breed successfully, as nests are submerged, developing embryos are deprived of oxygen, and juveniles get washed away.[81] Numerous predators, both mammalian and reptilian, may raid nests and eat crocodilian eggs.[95][96] Despite the maternal care they receive, hatchlings commonly fall to predation.[97] While the female is transporting some to the nursery area, others are picked off by predators that lurk near the nest. In addition to terrestrial predators, the hatchlings are also subject to aquatic attacks by fish. Birds of prey take their toll, and in any clutch there may be malformed individuals that are unlikely to survive.[95] In northern Australia, the survival rate for saltwater crocodile hatchlings is only twenty-five percent, but with each succeeding year of life this improves, reaching sixty percent by year five.[97]

Young saltwater crocodiles in captivity

Mortality rates are fairly low among subadults and adults, though they are occasionally preyed on by large cats and snakes.[97] The jaguar[98] and the giant otter[99] may prey on caimans in South America. In other parts of the world, elephants and hippopotamuses may kill crocodiles defensively.[19] Authorities differ as to whether much cannibalism takes place among crocodilians. Adults do not normally eat their own offspring, but there is some evidence of subadults feeding on juveniles and of adults attacking subadults. In Nile crocodiles, rival males sometimes kill each other during the breeding season.[95]

Growth in hatchlings and young crocodilians depends on the food supply, and sexual maturity is linked with length rather than age. Female saltwater crocodiles reach maturity at 2.2–2.5 m (7–8 ft), while males mature at 3 m (10 ft). Australian freshwater crocodiles take ten years to reach maturity at 1.4 m (4 ft 7 in). The spectacled caiman matures earlier, reaching its mature length of 1.2 m (4 ft) in four to seven years.[88] Crocodilians continue to grow throughout their lives. Males in particular continue to gain in weight as they get older, but this is mostly in the form of extra girth rather than length.[100] Crocodilians can live 35–75 years,[42] and their age can be determined by growth rings in their bones.[88][100]

Ecological roles :

Being highly efficient predators, crocodilians tend to be top of the food chain in their watery environments.[82] The nest mounds built by some species of crocodilian are used by other animals for their own purposes. American alligator mounds are used by turtles and snakes, both for basking and for laying their own eggs. The Florida red-bellied turtle specialises in this, and alligator mounds may have several clutches of turtle eggs developing alongside the owner's eggs.[101] Alligators modify some wetland habitats in flat areas such as the Everglades by constructing small ponds known as "alligator holes". These create wetter or drier habitats for other organisms, such as plants, fish, invertebrates, amphibians, reptiles, and mammals. In the limestone depressions of cypress swamps, alligator holes tend to be large and deep. Those in marl prairies and rocky glades are usually small and shallow, while those in peat depressions of ridge and slough wetlands are more variable. Man-made holes do not appear to have as large an effect.[102]

Gharial camouflaged with floating weed

In the Amazon basin, when caimans became scarce as a result of overhunting in the mid-20th century, the number of local fish, such as the important arapaima(Arapaima gigas), also decreased. These are nutrient-poor waters, and the urine and faeces of the caimans may have increased primary production by contributing plant nutrients. Thus the presence of the reptiles could have benefited the fish stock;[103] the number of crocodilians in a stretch of water appears to be correlated with the fish population.[104]

As pets :

Several species of crocodilian are traded as exotic pets. They are appealing when young, and pet-store owners can easily sell them, but crocodilians do not make good pets; they grow large and are both dangerous and expensive to keep. As they grow older, pet crocodilians are often abandoned by their owners, and feral populations of spectacled caimans exist in the United States and Cuba. Most countries have strict regulations for keeping these reptiles.[123]

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