In 2017 Remembrance Day for Lost Species will focus on pollinators, a broader theme than in some past years. This may be apt given reports that Earth may be on the brink of a full-spectrum ecological collapse unparalleled since the Dinosaur Age came crashing down. In the months leading up to Lost Species Day itself on 30 November, these regular “Lost Species of the Month” posts will commemorate a selection of extinct pollinators.
The notion of a lizard being a pollinator is rather strange. Unlike hummingbirds or bees, these creatures are hardly synonymous with dynamism or industry. An unfair characterisation of reptiles as sluggish, dull and abhorrent may have contributed to the role of certain lizards in pollination going largely overlooked.
Pollinator decline is rightly making headlines, but for some species the decline has already proven terminal. Two such creatures lived on the Indian Ocean island of Rodrigues. This isolated speck of land, along with the other Mascarenes, is often seen as a hotspot for recent island extinctions. However it might better be considered an unusually well-documented example, due to only having been settled during the seventeenth century.
The lost pollinators in question are the Rodrigues day gecko (Phelsuma edwardnewtoni) and the Rodrigues giant day gecko (Phelsuma gigas). Both common names are a little misleading. The Rodrigues day gecko was one of the largest members of its genus and the Rodrigues giant day gecko is thought to have been nocturnal!
Insects and nectar are believed to have comprised the bulk of these species’ diets. In the process of their nectar sipping, it is thought the geckos accumulated pollen on their faces and inadvertently spread it between flowers during their meals. This behaviour has recently been observed in other members of Phelsuma. Interestingly, one genus of Mascarene flowering plants produces coloured nectar, an extremely rare trait amongst plants. This nectar attracts Phelsuma geckos better than standard colourless nectar, suggesting coevolution between these plants and their reptilian pollinators.
Fig.1: Sculpted restoration of a Rodrigues giant day gecko. Image Wikimedia Commons by Abu Shawka
The Rodrigues giant day gecko (P. gigas) was the first of the two to become extinct. It was described in 1708 by François Legaut as being: “of greyish colour, and very ugly: they are as big and long as one’s arm.” In the opinion of this lizard enthusiast, Legaut was wrong to call this impressive-looking animal ugly, but was right to emphasise its size. The Rodrigues giant day gecko was the largest known gecko ever, potentially reaching over half a metre in length.
Like Mauritius and Réunion, Rodrigues was ravaged by European colonial activity. Its forests were burnt down to flush out its giant tortoises and clear land for livestock rearing. Along with habitat loss, Earth’s biggest gecko was dealt a sucker punch with the introduction of rats and cats, who feasted on the lizards and their eggs.
By 1840, Phelsuma gigas was confined to a few offshore islets. On the basis of five living geckos taken from one of these refugia, the species was formally described in 1842 by a French librarian named Liénard. One survived several months in captivity, refusing all food except sweetened water from a spoon. Liénard’s spoon-fed lizard was the last of its kind recorded alive. Nothing but a handful of assorted bones still remains.
Fig.2: Museum specimen of the Rodrigues day gecko. Image Wikimedia Commons by Jurriaan Schulman
The Rodrigues day gecko (Phelsuma edwardnewtoni) appears to have hung on a little longer than its larger relative. Legaut again provides the earliest record of these animals, who made quite a favourable impression on him and his companions:
“The palm trees and Latan palms are always laden with lizards about a foot long, the beauty of which is very extraordinary…the colour of each the most lively and bright of any of its kind…They are not mischievous, and so tame, that they often come and eat the melons on our tables, and in our presence, and even in our hands; they serve for prey to some birds. When we beat ‘em down from the trees with a pole, these birds would come and eat them from our hands, tho’ we did our utmost to hinder them; and when we offered to oppose them, they came on still after their prey”
Within two centuries of the publication of this curiously touching tale of island naivety, the Rodrigues day gecko had been eradicated from the main island. Habitat destruction and introduced predators were responsible. By the latter half of the nineteenth century rats were spreading across Rodrigues’ surrounding islets. Two last Phelsuma edwardnewtoni were collected in 1917 and sent to Paris, where they are preserved in alcohol for posterity. The species is thought to have succumbed to rats shortly thereafter. Today Rodrigues has no surviving endemic reptiles.
Elsewhere in the Mascarenes, geckos do continue to pollinate certain plants, particularly Trochetia flowers with their colourful nectar. The blue-tailed day gecko, a diminutive relative of Rodrigues’ lost lizards, still serves as a crucial pollinator of Mauritian Trochetia.
Recently it has been suggested that Gunther’s gecko, another large Mascarene day gecko species, could be introduced onto some of Rodrigues’ now rat-free islets. This rewilding project could serve two useful purposes. First, Gunther’s gecko is endangered, presently confined to a single area of less than two square kilometres. Establishing a second population of this animal could help ensure its survival. Second, Gunther’s gecko is considered an ecologically-comparable species to Rodrigues’ lost geckos. Potentially it could revive vanished interplays between plant and lizard. As with other rewilding proposals, only time will tell whether it will come to fruition.