Cuviers dwarf caiman

Appearance

Cuvier's dwarf caiman is the smallest living New World crocodilian. Males grow to a maximum length of about 1.6 metres while females do not usually exceed 1.2 metres in length. The largest specimen on record measured 1.72 m in length. This may be an underestimate of the animal's maximum size as nearly all large adults have lost the tips of their tails and the largest specimen measured in the Pantanal region had a snout-to-vent length of 1.125 m with an intact tail). An adult will typically weigh around 6 to 7 kg, around the same weight as a 6–12-month-old specimen of several larger species of crocodilians. The Cuvier's dwarf caiman has strong body armour on both the dorsal and ventral sides which may compensate for its small body size in reducing predation. The dermal scales that provide this protection have a bony base and are known as osteoderms.

The head has an unusual shape for a crocodilian with a dome-shaped skull and a short smooth, concave snout with an upturned tip, the shape rather resembling the head of a dog. The upper jaw extends markedly further forward than the lower jaw. There are four pre-maxillary and fourteen to fifteen maxillary teeth on either side of the upper jaw and twenty-one or twenty-two teeth on each side of the lower jaw giving a total of about eighty teeth. The neck is relatively slender and the dorsal scutes are less prominent than in the smooth-fronted caiman. The double row of scutes on the tail are small and project vertically. Adults are dark brownish-black with a dark brown head while juveniles are brown with black bands. The iris of the eye is chestnut brown at all ages and the pupil is a vertical slit.

The scutellation helps to distinguish Cuvier's dwarf caiman from Schneider's dwarf caiman
⤷ Post occipitals - Usually 2 rows
⤷ Nuchals - Usually 4 to 5 rows
⤷ Dorsals - 18 longitudinal rows and 6 to 10 transverse rows, neatly arranged, with 4 rows between hind legs
⤷ Ventrals - 21 to 22 longitudinal rows and 16 transverse
⤷ Tail - Single crest, usually 19 to 21 scales
⤷ Tail - Double crest, usually 9 or 10 rows
⤷ Tail - Lateral, small scales disrupt 2 or 3 rows

Naming

Common names include the musky caiman, the dwarf caiman, Cuvier's caiman and the smooth-fronted caiman, although the last of these is also used to refer to the closely related "Paleosuchus trigonatus". In the pet trade it is sometimes referred to as the wedge head caiman.

Distribution

Cuvier's dwarf caiman is native to tropical northern and central South America. It is present in the drainages of the Orinoco River, the São Francisco River and the Amazon River, and the upper reaches of the Paraná River and the Paraguay River. The countries in which it is found include Peru, Ecuador, Colombia, Venezuela, Guyana, Surinam, French Guiana, Brazil, Bolivia and Paraguay. The range of this species is rather larger than that of the sympatric smooth-fronted caiman as it extends into Paraguay and includes a larger area of Brazil.

Habitat

Cuvier's dwarf caiman is a freshwater species and is found in forested riverine habitats and areas of flooded forest around lakes. It seems to prefer rivers and streams with fast-flowing water but is also found in quiet, nutrient-poor waters in Venezuela and southeastern Brazil.

Reproduction

Adult Cuvier's dwarf caiman are usually found singly or in pairs. The breeding of this species has been little studied but it does not appear to be seasonal in nature. The female builds a mound nest out of vegetation and mud somewhere in a concealed location and lays a clutch of from ten to twenty-five eggs, hiding them under further vegetation. The incubation period is around ninety days and the sex of the hatchlings depends on the temperature of the nest during that time. When the eggs begin to hatch, the female opens the nest in response to the calls made by the young. Newly emerged juveniles have a coating of mucus and may delay entering the water for a few days until this has dried. Its continuing presence on their skin is believed to reduce algal growth. The female stays with the young for a few weeks after which time the hatchlings disperse. The young grow at the rate of about 8 to 10 cm per year and reach sexual maturity at around eight years.

Cuvier's dwarf caiman is considered to be a keystone species whose presence in the ecosystem maintains a healthy balance of organisms. In its absence, fish such as piranhas might dominate the environment. The eggs and newly hatched young of Cuvier's dwarf caiman are most at risk and are preyed on by birds, snakes, rats, raccoons and other mammals. Adult caimans are protected by the bony osteoderms under the scales and their main predators are jaguars, green anacondas and large boa constrictors.

Food

Cuvier's dwarf caiman is mainly nocturnal, and adults feed on fish, amphibians, small mammals, birds, crabs, shrimps, molluscs and other invertebrates which they catch in the water or on land. Juveniles eat fewer fish but also consume crustaceans, tadpoles, frogs and snails as well as land invertebrates such as beetles. The prey is mostly swallowed whole and is ground up by stones in the gizzard. In the Pantanal, Cuvier's dwarf caiman aestivates in burrows during the dry season and is able to maintain its temperature at around 22 °C for days at a time.