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The spectacled caiman (Caiman crocodilus) is one of five caiman species in the Amazon River drainage system. This species has a typically crocodilian appearance, but its maximum size is rather smaller than the black caiman and other members of its family. The largest males reach about 8 feet (2.5 m) but average about 6 feet (2.1 m). Females are about two thirds the size of males.

The name "spectacled" comes from a bridge between the orbits of the eyes that looks rather like a pair of spectacles. The upper eyelids bear bony ridges, conferring a dinosaur-like appearance.

Adult spectacled caimans are uniformly olive-green whereas juveniles are khaki green with yellow and black bands along the stomach and base of the tail. As with other crocodilians, this camouflage becomes less distinct in the adult.

Of particular note is this species' chameleon-like ability to change color. Although the effect is subtle, other crocodilians show this ability, which arises from migration of black pigment in skin cells. Caiman crocodilus is classified into several different subspecies which vary in size and skull morphology, as well as skin color.

The spectacled caiman is the most widely distributed crocodilian in the Americas. It is found throughout the Amazon River basin from southern Brazil up through Central America to southern Mexico. The far west of its range is limited by the Andes mountain range in Peru, but more northerly, in Ecuador and Colombia it is found to the Pacific coast.

This species prefers quiet riversides and swampy areas where it lurks among floating vegetation, although it might be found in any wetland habitat.

The spectacled caiman is an opportunistic predator, taking advantage of whatever prey is most abundant. Its main diet comprises fish, although adults are known to take large mammals such as capybara and peccary.

As juveniles grow in size, they graduate up to approriately sized prey. They begin with tiny aquatic invertebrates (insects, crustaceans, molluscs). Larger juveniles prey on various vertebrates such as fish, amphibians, reptiles and water birds, that make an increasing proportion of the diet. Only mature caiman are able to tackle large mammals.

Caimans adapt to prevailing environmental conditions and during the dry season, decrease predatory activity. In dire situations they may resort to cannibalism.

As top predator caimans play a pivotal role in the balance of the ecosystem. In the absence of a top predator, prey species' populations can veer out of control and cycle wildly. Dominant species tend to take over. Where caimans are heavily hunted, some researchers have reported that piranha numbers tend to be higher. Caimans also serve as a conduit for cycling nitrogen through the ecosystem, as their waste serves to fertilize aquatic plants. (Nitrogen is an essential nutrient for plant growth.)

Caiman reproduction is closely matched to the Amazon's annual cycle of wet and dry seasons. Eggs (of females) and testes (of males) grow larger as the rainy season draws near around May. From May to August, caiman courtship and mating behavior peaks. Egg-laying follows, taking place mostly between July and August. Close by the river's edge, Females dig a shallow pit in sandy soil with their front legs and lay 15 to 50 eggs. Clutch size averages 25. This is then covered with a mound of dead leaves, reeds and grasses.

Heat from the nest's decaying vegetation helps maintain the nest at a constant temperature. Unlike most animals, the sex of baby crocodiles (and some other reptiles) depends on the temperature in the nest, temperature-dependent sex determination (TSD). A warm nest will result in more males, whereas a cooler nest skews the ratio toward females. The location of the nest can therefore influence the numbers of males and females that hatch. A nest under cover will have more females than a nest in the open. The phenomenon may prove useful in reptile conservation since the developing eggs can be treated with sex hormones to result in a majority of females.

Females sometimes nest in groups, even sharing nests. This spreads the risk for females since a nest predator will be less likely to take all the eggs of a particular female. Eggs may be eaten by lizards such as the tegu (Tupinambis spp.) which often destroys the entire nest and may damage four fifths of nests in its range. To reduce damage caused by predators the female caiman lurks close by and will chase off a potential marauder.

Due to the seasonal timing, young caiman have abundant prey upon hatching, about 90 days after laying. Females provide a degree of parental care as the juveniles stay in here vicinity until they are large enough to fend for themselves. Groups of females that shared nest sites may also share in caring for young.

Female caiman breed between 5 to 10 years of age, once they have reached 3 or 4 feet in length. Males reach sexual maturity at a larger size but as they grow faster, are capable of breeding at the same age. The social rank of the individual determines breeding success since lower rank animals feed less and grow more slowly, hence take longer to reach breeding age.

With a wild population estimate in excess of 1,000,000, the spectacled caiman is the commonest of all crocodilian species, but is locally threatened in many parts of its range.

It's not hard to hunt caiman. A hunter patrols a river bank at night, shining his flashlight among the reeds, looking for a lurking caiman's tell-tale eye, shining red like a hot coal. He just shoots in the right direction, waits for the thrashing to stop and motors over to hitch the dead animal into his boat.

For tourists hunting caiman, the procedure is a bit more complicated. The tricky part is to approach cautiously, while all the time keeping the flashlight on the bright red spot. This apparently mesmerizes the beast. If all goes according to plan, the caiman will remain paralyzed by the light while the boat approaches. The guide will then lean over the boat, hanging on to whatever is to hand, to grab the hapless creature. After a round of picture taking and brief overview of caiman natural history, the captive is released to no apparent ill-effect. Ecotour operators hope this victimless hunting will pay off as the close encounters help educate and inform about these beautiful creatures.

Excessive hunting of other caiman species (such as the black caiman) has helped the spectacled caiman, which has moved into its competitors' habitat. Most of the spectacled caiman's hide is too rough to make good leather. Only the sides are suitable, so they were not as intensively hunted as other species. This changed as those species became rarer, so to supply the trade, more spectacled caimans were hunted. Today this species provides most of the crocodilian leather used in the United States. Illegal hunting fuelled by rising demand in Asia is the main threat. However, the species' adaptability, high reproductive rate, and the increase in habitat resulting from human activities (e.g., dams), have dampened the effect of excessive hunting.

Conservation of caimans is complicated by taxonomy (classification) which has yet to be fully resolved. Morphological studies have led to the recognition of several sub-species, some of which are not accepted by experts, others are. Because conservation decisions often depend on a desire to preserve particular species, such information is essential in creating reserves and parks that will do the intended job.
Populations in the Brazilian Pantanal, Colombia and Venezuela seem relatively healthy, although Central American populations seem severely depleted. Wildlife managers question the long-term prospects for farming and ranching of caiman populations, although such programs have succeeded in Africa with the Nile crocodile. The limited utility of the spectacled caiman's hide means a lot of animals are needed to meet demand. The best approach to long-term conservation of caimans may be the creation of sustainable use preserves that permit regular culling of local populations. This may provide an income for local people as well as incentive to conserve natural habitat.


Florida Museum of Natural History: Caiman crocodilus
Reptile Conservation International
Gulf States Marine Fisheries Commission: Caiman crocodilus (Linnaeus)
Wikipedia: Spectacled caiman
Digimorph: Caiman crocodilus (spectacled caiman): skull
Wikipedia: Alligatoridae
FAO: 3.3.1 Caiman crocodilus (spectacled caiman) Crocodiles of the World - Caiman
ITIS Report: Caiman crocodilus crocodilus (Linnaeus, 1758)
Institute for Tropical Ecology and Conservation: Caiman crocodilus Narrow-snouted Spectacled Caiman
The Taxonomicon: Caiman crocodilus taxonomy
CITES: Colombia - Export of Skins of Caiman crocodilus
Zoofarm de Colombia: The Spectacled Caiman
Geological Society of America: Triche, Nina E., Osteological and Ontogenetic Variation in Caiman crocodilus
The Herpetologists' League 2001: Stephen D. Busack and Sima Pandyab. Geographic Variation in Caiman crocodilus and Caiman yacare (Crocodylia: Alligatoridae): Systematic and Legal Implications. Herpetologica 57(3): 294-312
Calderon M.L., De Perez G.R., Ramirez Pinilla M.P. (2004) Morphology of the ovary of Caiman crocodilus (Crocodylia: Alligatoridae). Ann Anat. 186(1):13-24.
Ebbesson S.O., Goodman D.C. (2001) Organization of ascending spinal projections in Caiman crocodilus. Cell Tissue Res. 215(2):383-95.

Mainly photos
Animal Diversity Web: Caiman crocodilus (spectacled caiman) Common Caiman
Photovault: Caiman (Caiman Crocodilus) Paleosuchus Caiman crocodilus (Linnaeus, 1758) South America Wildlife Photo Gallery, Jacaré - Caiman crocodilus
Michael Rothhaar, Ag Krokodile

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