For the past few years the authorities of Chiayi County, southwestern Taiwan, have paid bounties to citizens for brown anoles they collect. Every year the bounty per lizard has decreased and yet they spend their budget and the brown anole persists. This year is the same – a lower bounty – but with a slight difference; the green iguana is now also on the list. In theory, it would be ideal if the invasive lizards can be exterminated, but in reality, I am convinced, they will fail. The brown anole exists in southwestern and eastern Taiwan, and simply targeting them in one location will simply retard their dispersal to new localities (and even with the bounty in place, their distribution is extending). We recently published the results of a study in which we compared brown anole specimens from southern and eastern Taiwan, and we found that there are some variations, most likely due to adaptations to the local habitats (no surprise there!). What this means is that in Taiwan, if brown anoles can reach (either by natural dispersal or with the help of people) open disturbed habitats, with structures that can be used as perches, they will most likely adapt and establish new populations.
And then I wonder why is the brown anole singled out for extermination. Eutropis multifasciata, a relatively large invasive skink, also exists in Chiayi County. Due to its size, it has greater abilities than the brown anole to compete with and prey upon native lizards and arthropods, and yet, they are not on the list. People regard Hemidactylus frenatus, a very common gecko species in urban areas in central and southern Taiwan, as a native species, not realizing that it too is an invasive species.
My honest opinion is they have to accept that just like Hemidactylus frenatus, Anolis sagrei will spread in Taiwan and become a common sight in areas disturbed by humans. They will become (and in many ways already are) part of local ecosystems as competitors, predators and prey. Conservation efforts should thus rather be directed at the re-establishment and conservation of large areas of secondary forests in disturbed lowland areas of Taiwan. This would not only contribute to the conservation of native forest species, but such areas will also function as reservoirs for species like Japalura swinhonis that can compete with Anolis sagrei, as well as being barriers for its spread. People should also be encouraged to be more tolerant towards snakes, in particular non-venomous species such as Lycodon (Dinodon) rufozonatum rufozonatum, Lycodon ruhstrati ruhstrati, and Sibynophis chinensis chinensis, which can prey upon brown anoles. And, finally, an important part in the conservation efforts of native urban wildlife is to develop a better appreciation among the general public of native birds and lizards in urban gardens and parks, and to reduce the impact on these animals by their pets, especially domestic cats (Felis catus), which may prey on them.
Just for interest sake, here is a current list of exotic invasive lizards in Taiwan: