Saturday, 18 April 2015

Lizards 8: Standings Day Gecko

In Madagascar and nearby islands of the Indian Ocean some of the most visible reptiles are the various species of Phelsuma geckos. Usually referred to as day geckos (although at least one species on Mauritius is nocturnal) they are mostly small lizards, living in trees and bushes. There are numerous species, many with ranges limited to a single island or patch of forest, and consequently many are classed as threatened or worse by the IUCN. At least 2 species are extinct, one of which was the largest known species, the Rodrigues Giant Day gecko, which reached at least 40cm. .
At Bristol, 2 species are on display, the tiny Yellow-Headed Day Gecko P.klemmeri and Standing’s Day Gecko P.standingi.

Standings Day Gecko is one of the largest living Phelsuma species, reaching a length of 28cm. They originate from spiny forest in south west Madagascar. This unique habitat is home to numerous endemic species, notably Verraux’s sifaka. As with the rest of Madagascar, the forests are under severe pressure from the human population, especially charcoal burning, logging for construction and conversion to cattle pasture. As a result, P.standingi is currently on the IUCN Red List as Vulnerable.

In the wild, Standings’ Day Geckos live among the spines on the highest branches, often exposed to bright sunlight. Perhaps because the trees are leafless for a large part of the year and food resources are consequently limited for a large lizard, both sexes are territorial, males driving off males and females driving off competing females. As a group, day geckos are often brightly coloured, with markings in various combinations of green, blue, and yellow, but adult P.standingi are mostly a dull grey-green. Hatchlings and juveniles are more brightly coloured, and this difference may perhaps help to reduce aggression between adults and their offspring. It seems likely that young hatch during the wet season, when there is more food around, but I do not know of any specific research on this. Males and females are easily distinguished, as females have prominent endolymphatic chalk sacs in the neck, which store calcium for their hard-shelled eggs.

Phelsuma species have a rather specialised diet analogous to many tropical birds. Age component of their diet is nectar from flowers, and probably aphid honeydew, which they eagerly consume. As a result some species, such as those on Mauritius and probably elsewhere, are important pollinators of such flowers as hibiscus. This diet is low in protein, and they supplement the nectar with fruit and especially small insects. Given their habitat, Standings' Day Geckos probably have a higher proportion of insects in their diet as for much of the year nectar would be hard to come by.

As with most geckos, Standings’ lay two eggs at a time, under loose bark or in tree holes. Incubation takes around 70 days, and the young reach maturity at one year in captivity. AS with many animals with a fairly low reproductive rate they are long lived, and can live over 20 years in captivity.

(images are mine)

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