Ameiva ameiva

Submitted by rludwick 10 Feb
Scientific name:  Ameiva ameiva
Common names
Common names:  Giant Ameiva [en]
Overview: 

Ameiva ameiva is a relatively large teiid lizard that may reach nearly 20 cm in snout-vent length and 64 cm in total length. Its snout is characteristically pointed, and its tail is very long, comprising up to 70% of its total length. Coloration in this species is distinctive and is described in detail in “Morphology.” In brief, adult males have greenish to orange spots over a green or brown background, while juveniles and adult females have approximately 4-5 longitudinal stripes on their backs and spots on their flanks. This species is very active, and it is most commonly found foraging for food on or near the ground between midmorning and early afternoon. It occupies a wide range of habitats, from rainforests to dry, open areas, and it seems to tolerate some human habitat disturbance, thriving in certain types of plantations and clearings.

Associations
Associations: 

As one of the larger lizards in its geographic range, Ameiva ameiva can eat a wide variety of smaller animals. Its diet consists primarily of arthropods and may contain high proportions of grasshoppers, crickets, roaches, beetles, spiders, insect larvae, or termites. However, it may also eat smaller lizards, as well as “aquatic insects, crawfish, frogs, and snails” (Vitt and Colli 1994). Like other Ameiva species, the primary predators of A. ameiva are probably snakes (Hirth 1963).

Behaviour
Behaviour: 

Ameiva ameiva is active primarily during the late morning and early afternoon. Like most teiid lizards, it is a highly active forager, and may dig into the soil or leaf litter to reach food that would be inaccessible to a purely visually oriented predator. This species is ectothermic, using behavioral means to maintain an average body temperature of 37.9 ± 0.09 °C that remains relatively constant throughout the day and over its broad geographic range (Vitt and Colli 1994).

Conservation status
Conservation Status: 

As of January 1, 2011, the conservation status of Ameiva ameiva has not been assessed by the IUCN Red List (IUCN 2010).

Diagnostic description
Diagnostic Description: 

The large size and distinctive dorsal coloration of Ameiva ameiva are usually sufficient to identify this species. Adult males have “numerous greenish yellow to orange spots on a blue green to brown ground color” (Savage 2002) dorsally. Young males and all females have “two narrow creamy white lateral and two ventrolateral stripes and a broader dull gray green to brown vertebral stripe” (Savage 2002); adult females may have light spots between these stripes. Additionally, A. ameiva is the only Central American macroteiid to have “five large shields in the parietal row combined with a longitudinal ventral count of 10 to 12” (Savage 2002).

Distribution
Distribution: 

Ameiva ameiva has a very wide distribution, extending from southwestern Costa Rica and the southern Lesser Antilles through most of northern South America to northern Argentina, Paraguay, and southeastern Brazil. Its native range includes Panama, Colombia, Venezuela, Brazil, Paraguay, northern Argentina, Surinam, French Guiana, Guyana, Bolivia, Ecuador, Peru, Trinidad and Tobago, Swan Island, Islas San Andrés, Providencia, Margarita, St. Vincent, the Grenadines, and Grenada (Savage 2002; Tway 2003). This species has also been introduced to Florida (Savage 2002), apparently through the pet trade.

Evolution
Evolution: 

In a phylogenetic study using partial mitochondrial 12S and 16S rRNA sequences, Hower and Hedges (2003) found Ameiva ameiva to be the most basal member of its genus. Interestingly, of the remaining fifteen species examined in this study, two other mainland species (A. festiva and A. undulata) were sister to the remaining thirteen species, which came from the West Indies. This pattern suggests that the Ameiva species in the West Indies are derived from lizards that colonized the islands from the Central and South American mainland (Hower and Hedges 2003).

Habitat
Habitat: 

Ameiva ameiva occurs over a broad geographic range and in a wide variety of habitats; in Brazil, these include caatinga, cerrado, Amazonian rain forest, and Amazonian savanna ecosystems. It appears to be most common in open areas, including in recently disturbed habitats such as forest edges and agricultural plantations (Vitt and Colli 1994, Savage 2002). In fact, its apparent preference for open habitats over woodlands has led Vitt and Colli (1994) to suggest that human habitat alterations such as deforestation and agricultural development may actually allow populations of this species to expand more than they might otherwise.

Life cycle
Life cycle: 

Ameiva ameiva is thought to reach sexual maturity within a year after hatching. Its total lifespan may exceed three years, although predation prevents many individuals from reaching this age (Vitt and Colli 1994).

Look alikes
Look alikes: 

The size and coloration of adult Ameiva ameiva, especially males, are relatively distinctive. However, juvenile A. ameiva may superficially resemble the juveniles of some other teiid species. Juvenile A. ameiva can be distinguished from juvenile Cnemidophorus by the number of light dorsal stripes: Ameiva ameiva has four such stripes while Cnemidophorus has nine or ten. Cnemidophorus also has “greatly enlarged gular collar scales” (Savage 2002) which are less pronounced in A. ameiva. The juveniles of A. ameiva may also resemble those of A. quadrilineata. However, the dorsum and flanks of A. ameiva may have light spots which are absent in A. quadrilineata, and A. ameiva has five enlarged parietal shields while A. quadrilineata has only three (Savage 2002).

Morphology
Morphology: 

Ameiva ameiva is a medium- to large-sized lizard with a large head and fat belly relative to the rest of its body. The border between the head and the neck is often difficult to recognize, except in larger males which have a jowl-like feature due to hypertrophied jaw muscles. In terms of scalation, the head plates are smooth and the nostril is located in the nasal suture. The postnasal scales touch one prefrontal, and there is only one frontal plate. There are four supraoculars, and the supraorbital semicircles do not exceed the posterior margin of the frontal. The inner parietal scales are “in broad contact” (Savage 2002) with the interparietal and frontoparietals, and the parietal row contains five large plates. The anterior gular scales are much larger than the posterior gular scales, and the scales of the midgular patch are irregular and barely enlarged. The posterior gular fold contains two rows of collar scales, which are smaller or equal in size to the posterior gular scales. The scales in the center of the posterior surface of the forearm are slightly enlarged. The ventral scales occur in 10-12 longitudinal rows, there are 25-41 femoral pores, and there are 26-36 lamellae under the fourth toe (Savage 2002).

Juveniles have two narrow, cream- to yellow-colored lateral and ventrolateral stripes, often in addition to a wider brown vertebral stripe. Small, light spots are present between the lateral and vertebral stripes and below the lateroventral stripes, and the tail is brown. Adult females have a more pronounced spotted pattern on their flanks, as well as an irregular pattern of incomplete dark bars in the middorsal area. Adult males are not striped but instead have an extensive pattern of greenish to orange spots; the upper surface of the thighs of adult males is spotted, as opposed to mottled in juveniles and females. All members of this species have a generally greenish ground color, a lighter (white or light blue) venter, and a light brown iris (Savage 2002).

In addition to coloration, A. ameiva is also sexually dimorphic in size. Males generally grow larger than females, and while members of this species have large heads in general, the heads of males are larger relative to body size than those of females. The heads of juveniles are even larger relative to body size, and they decrease in relative size as the lizards mature. It has been hypothesized that the large heads of juveniles evolved from competing for prey with sympatric teiid lizards, while the large heads of adult males may instead be due to sexual selection, but these ideas have yet to be rigorously tested (Vitt and Colli 1994).

Physical description
Size: 

Ameiva ameiva can reach 640 mm in total length, with a long tail accounting for approximately 70% of this length. In terms of snout-vent length, adult males range from 90-197 mm and females are slightly shorter, ranging from 80-157 mm (Savage 2002).

Reproduction and life history
Reproduction: 

Ameiva ameiva becomes sexually mature by the age of one year, and likely reproduces multiple times during its lifetime. This species appears to prefer to nest in “well-drained sandy soils” (Vitt and Colli 1994). Clutch sizes average between 3-6 eggs, but extremes of 1 and 11 eggs have been documented. This species reproduces most readily when rainfall is abundant, thus, the seasonality of its reproductive behavior varies substantially among the different climates it inhabits. In areas such as the Amazon rain forest where rainfall is abundant throughout the year, or in Brazilian caatinga habitats where rainfall is scarce and unpredictable, A. ameiva reproduces year-round. However, in habitats with more pronounced seasonality such as Brazilian cerrado or Amazon savanna, reproduction is concentrated during the wet season, although it may continue to occur at reduced levels during the dry season. Significant differences in egg size and clutch size have been observed between different populations of A. ameiva in different habitats, but these trends appear complex and remain poorly understood (Vitt and Colli 1994).

Trends and threats
Trends: 

Unlike most species, deforestation and land clearing may actually increase the amount of suitable habitat available to Ameiva ameiva because of its tolerance for dry and open landscapes. Thus, it may have colonized Panama and Costa Rica only relatively recently, following the development of large banana farms (Savage 2002).

Uses
Uses: 

Like many lizards, Ameiva ameiva may be sought after by hobbyists and collectors. This species is often raised in captivity.

References
References: 
Hirth, H.F. 1963. The ecology of two lizards on a tropical beach. Ecological Monographs 33(2): 83-112.
Hower, L.M. and S.B. Hedges. 2003. Molecular phylogeny and biogeography of West Indian teiid lizards of the genus Ameiva. Caribbean Journal of Science 39(3): 298-306.
IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. . Downloaded on 1 January 2011.
Savage, J.M. 2002. The Amphibians and Reptiles of Costa Rica: A Herpetofauna between Two Continents, between Two Seas. Chicago, IL: The University of Chicago Press, pp. 508-510.
Tway, M. 2003. Ameiva ameiva: Giant Ameiva. Institute for Tropical Ecology and Conservation. Last updated 20 February, 2003.
Vitt, L.J. and G.R. Colli. 1994. Geographical ecology of a Neotropical lizard: Ameiva ameiva (Teiidae) in Brazil. Can. J. Zool. 72: 1986-2008.
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Attribution
Rights holder:  Rachelle Ludwick and Lee Dietterich
Author(s):  Rachelle Ludwick
Author(s):  Lee Dietterich
Editor(s):  Luke Mahler

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