Geckos: The Animal Answer Guide

10. Human Problems (from a gecko’s viewpoint)

108 Chapter 10 Human Problems (from a gecko’s viewpoint) Are any geckos endangered? Yes, a number of geckos are considered endangered. The IUCN (International Union for Conservation of Nature) maintains a Red List of threatened species, which in 2011 included 55 geckos, or less than 4 percent of recognized species, in the endangered or critically endangered categories (Table 10.1). The majority of these include species on islands like Madagascar (19 species) and New Caledonia (14 species), including many species of Day Geckos (Phelsuma) and Nimble Geckos (Dierogekko), respectively. However, this does not give an accurate view of all the geckos that are really endangered, as fewer than one-third of all geckos have been assessed by the IUCN and in some cases assessments are out of date. In addition, so little information is known about many geckos that their conservation status cannot be meaningfully assessed. Many countries have their own Red Lists, and these list many more species as endangered. As an example, the Salt Marsh Gecko (Cryptactites peringueyi), considered critically endangered in its South African homeland, has yet to be assessed by the IUCN. Other species may be doing well in parts of their range but not in others. For instance, Tokay Geckos have been considered endangered in China since 1998 but are not listed as threatened by other countries in which they occur. What is the rarest gecko? Many geckos are so poorly known that their rarity is hard to determine. Some species, such as the Indian Bent-toed Gecko, Cyrtodactylus malcolm- 109 Human Problems smithi, are known only from one or two specimens collected more than a century ago. While scientists’ failure to find these geckos again may mean that they are extinct, it more likely reflects our lack of knowledge about the distribution and biology of the species. This can be seen in the case of the New Caledonian Crested Gecko, Correlophus ciliatus. This distinctive species was first described in 1866 and was reported to be common for about a decade after its discovery. Then it was not seen again for more than 100 years, despite many searches, and was considered likely to be extinct. In 1992, it was rediscovered and since then has been found to be locally abundant . It has since become one of the most widely bred and kept of gecko species. Another New Caledonian giant gecko, Rhacodactylus trachycephalus, however, really does appear to be one of the rarest of all geckos. It has a very small distributional range, occurring only on one or two very small (less than 0.4 square miles or 1 square kilometer) offshore islands and has a low reproductive rate, giving live birth to at most one set of twins per year. These factors are coupled with major threats: the islands where they live have introduced populations of rats, which are known to prey on geckos, and the geckos are in high demand in the pet trade and are easily accessed by smugglers. Have any geckos become extinct because of humans? The giant Hoplodactylus delcourti of New Zealand is probably extinct. Its demise was probably the result of a combination of natural causes (the decrease in the range of giant kauri trees due to climate change over the The restricted ranges of many geckos place them at risk for extinction . The Néhoué Nimble Gecko (Dierogekko nehoueensis) lives in a small area of northern New Caledonia . All members of this genus are threatened or endangered, chiefly due to threats from habitat destruction through mining and other human uses. Table 10.1. IUCN (International Union for the Conservation of Nature) list of geckos in the three threatened status categories. Two other geckos (Hoplodactylus delcourti and Phelsuma gigas) are listed as extinct by the IUCN. Species occurring on islands are indicated by an asterisk (*). Recent changes in taxonomy have resulted in the movement of Rhacodactylus ciliatus and R. sarasinorum to the genus Correlophus, R. chahoua to Mniarogekko, and Cyrtopodion amictophole to Mediodactylus. Family VU (vulnerable) EN (endangered) CR (critically endangered) Carphodactylidae Nephrurus deleani Phyllurus gulbaru Diplodactylidae Correlophus ciliatus* Bavayia exsuccida* Dierogekko inexpectatus* Mniarogekko chahoua* Bavayia goroensis* Dierogekko kaalaensis* Toropuku stephensi* Bavayia ornata* Dierogekko koniambo* Correlophus sarasinorum* Dierogekko nehoueensis* Dierogekko validiclavis* Dierogekko poumensis* Eurydactylodes symmetricus* Dierogekko thomaswhitei* Rhacodactylus trachyrhynchus* Eurydactylodes occidentalis* Oedodera marmorata* Pygopodidae Aprasia rostrata Aprasia aurita Delma impar Delma labialis Delma torquata Ophidiocephalus taeniatus Paradelma orientalis Eublepharidae Goniurosaurus kuroiwae* Gekkonidae Ailuronyx trachygaster* Ebenavia...