Anolis oculatus

Anolis oculatus

Dominica anole, Dominican anole, Eyed anole, Zandoli

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SPECIES
Anolis oculatus

Anolis oculatus, the Dominica anole, Dominican anole, eyed anole or zandoli, is a species of anole lizard. It is endemic to the Caribbean island of Dominica, where it is found in most environments. The species is found in a diverse range of color forms, which one herpetologist once classified as four subspecies, which most other scientists did not recognise because the forms gradually inter-grade with one another. Two later researchers have instead promoted the "ecotypes" concept, hypothesizing the color forms are maintained by the ecological conditions of the surrounding environment, despite being genetically indistinguishable. The morphology of some traits is subject to clinal variation, gradually changing from one side of the island to the other, or from sea level to the hilltops. The ground color ranges from pale tan or yellow to deep green or brown. It also has patterned markings that range from light-colored speckling to complex marbled patterns, and some populations also have large black-ringed "eye" spots on their flanks.

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The Dominican anole spends much of the time in trees but mainly hunts on the ground. Small insects make up the bulk of its prey, with soft-bodied invertebrates and small vertebrates hunted less frequently. Long-living and late maturing for anoles, the Dominican anole can usually breed from around two to three months of age. Females lay eggs, and breeding can occur at any time of year. Clutches number one or rarely two eggs and are laid under rocks or leaves on the ground. Although presently widespread and common on Dominica, in 2007 some authors opined that it may face competition from A. cristatellus, an anole from Puerto Rico, which was introduced a few years earlier.

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Appearance

The Dominican anole is medium-sized for anoles, with a maximum snout-vent-length (SVL) in males of 61–98 mm (2.4–3.9 in) depending on the population (with larger sizes correlating with higher altitudes), and tails of at least equal length; females are smaller in all populations. Adult males have a tail crest and a prominent, extensible throat fan that is often a bright yellow or orange. The throat fan is only rudimentary in females, and less brightly colored. Some may have bright blue eyes. Dominican anoles are capable of slight color change, but not as much as some other anoles.

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Their ground color varies from pale tan or ash gray to deep brown or green. Markings also vary significantly. Adult males in all populations have some combination of white or light-colored spotting distributed over most of their bodies. This manifests in different populations as small, evenly distributed spots; scattered groups of white scales; or streaks that run together in a marbled appearance. Males in some populations additionally have larger lateral spots ringed by irregularly shaped black splotches. Markings on females and juveniles are significantly lighter or less distinct, and black spots are extremely uncommon. Females and juveniles may additionally have lateral streaks or mid-dorsal stripes.

The cause of the variability of the anole has been the subject of much study. Its morphological traits vary independently from each other, such that the presence of one trait does not predict the presence of another. Some traits vary altitudinally and others longitudinally, or may correlate with ecological factors such as rainfall and vegetation type. Populations in drier habitats tend to be paler in color with marbled or blotched markings, while those in wetter habitats are deeper green, hence the usage of the term "ecotype" by Malhotra et al.. The same patterns are also seen in the highly variable A. marmoratus on Guadeloupe, a neighboring island group that has a range of habitats comparable to Dominica.

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Distribution

Geography

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The Dominican anole is restricted to the island of Dominica, one of the few islands in the Lesser Antilles to have retained its original reptile and amphibian fauna over the last 200 years. It is one of two lizard species endemic to Dominica, the other being the Dominican ground lizard. It is the only native anole species on Dominica. It is present in all habitats and areas of the island up to around 900 m elevation and is generally abundant, though it is tending towards extirpation from the southwestern coastal region due to an invasive anole species (see Conservation ). The coastal woodlands of Dominica have been particularly noted as unusually favorable for reptiles, with a biomass among the highest recorded for terrestrial reptile populations; Dominican anoles have been estimated to occur in that environment at a mean density of 2148 per hectare.

Anolis oculatus habitat map
Anolis oculatus habitat map
Anolis oculatus

Habits and Lifestyle

Dominican anoles are semi-arboreal, and mainly forage on the ground for food. Its diet mainly consists of insects, but varies by habitat and season based on the available food, and with the size of the individual. It may also eat fruit and even small vertebrates. In xeric woodland habitats on Dominica's Caribbean coast, it mainly feeds on tiny ants, termites, springtails and barklice. Montane populations, which reach larger sizes, rely more on larger prey such as Oligochaeta (earthworms) and Orthoptera (crickets and grasshoppers), although smaller adults and juveniles in rainforest environments will also mainly feed on ants.

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The main predators of Dominican anoles are Alsophis antillensis, a species of "racer" snake, and birds including the mangrove cuckoo, thrashers, and kingbirds, all of which are mainly found in coastal regions.

Both males and females are territorial. Male territories are roughly twice the size of female territories, and males will typically mate with females with overlapping territory. Female territories may overlap in areas with high population densities. Research has shown gene flow within the species to be determined by male migration, which suggests that females do not have significant mate choice preferences. Migration probably occurs during the juvenile stage, as male and female adults are mostly sedentary.

During active periods, Dominican anoles typically perch on a tree or other vertical object, facing downwards to scan the ground for food or other lizards, though this perch makes them vulnerable to predators. From this perch, males will extend and retract their brightly colored throat fans, both to attract mates and to ward off competitors. Males will also bob their heads or perform what look like "push-ups" using their front legs. An invading male may cause a confrontation, during which they will circle at close quarters, inflating their bodies and gaping their mouths to appear larger and menacing. Physical contact during these confrontations is unusual and brief when it occurs, rarely resulting in physical injury. The invader will usually retreat after these confrontations even if it is larger than the defending male.

Activity patterns vary between populations, though the species as a whole is generally most active during the cooler hours of the day. In xeric woodland on Dominica's west coast, it is active throughout the day with peaks at dawn and dusk, while in rain forest populations, it is typically inactive during the middle of the day, remaining at high perches. At night, the Dominican anole climbs to the tips of branches and sleeps clinging to leaves, where heavier nocturnal predators cannot reach them.

Dominican anoles in some populations are very tolerant of humans, allowing them to approach closely before retreating. It will seek shelter under stones or other ground litter.

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Lifestyle

Diet and Nutrition

Mating Habits

Dominican anoles are relatively long-living and late maturing compared to mainland anole species. Males mature at a size of 35 mm SVL, and females mature at 40 mm SVL, which they are likely to attain at an age of two or three months old. They breed throughout the year, with a peak at the end of the dry season, particularly in areas such as the north Caribbean coast that have more seasonal rainfall variation. Females are oviparous, and lay multiple clutches of eggs each year, with a short period between clutches. Females in captivity have produced eggs every 14 days. Each clutch typically contains only one egg, though clutches of two can occur without apparent relationship to season, location, or size of the females. Egg production alternates ovaries and overlaps cycles, with one ovary ending its cycle after the opposite ovary has begun. Eggs are laid sheltered under ground litter such as rocks or leaves.

Population

Conservation

The Dominican anole is threatened by an introduced competitor, Anolis cristatellus, which established itself in Dominica between 1997 and 2002, and as of 2007 had begun to supplant it in the southwestern coastal area surrounding the capital, Roseau. Within this area the Dominican anole has become absent or rare. Because that is almost the entire range of the southern ecotype, some authors recommended a captive breeding program to preserve this color form. These authors furthermore fear that the Dominican anole may eventually face extirpation from much of Dominica, except for specific environments that A. cristatellus tends not to prefer, such as forests or mountainous areas.

References

1. Anolis oculatus Wikipedia article - https://en.wikipedia.org/wiki/Anolis_oculatus
2. Anolis oculatus on The IUCN Red List site - https://www.iucnredlist.org/species/178342/18967200

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