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.
HABITAT AND DISTRIBUTION
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.
FEEDING AND DIET
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
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.