Author: Gerrut Norval Page 1 of 2

A familiar face – a brown anole male from my study site in southwestern Taiwan.

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.

Me with a green iguana (Iguana iguana) that was removed by firefighters from someone’s garden in Chiayi City.

A sun skink (Eutropis multifasciata) from Tainan City, southwestern Taiwan.

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.

Hemidactylus frenatus is a very common species in southern Taiwan, where they are often seen near external lights on the walls of buildings.

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:

Anolis sagrei

Eutropis multifasciata

Hemidactylus frenatus

Iguana iguana

Lepidactylus lugubris

Physignathus cocincinus

A dorsal view of the brown anole male that I collected on the 19th of July 2002.

On the 19th of July, 2002, I collected a brown anole (Anolis sagrei) male from the edge of a rice paddy next to a tarred road in Santzepu, Sheishan District, Chiayi County, Taiwan, as part of a diet and reproductive cycle study. As I removed it from the fine-meshed fishing scoop net, which I used for capturing it, I found that it had two tails. I later found that even though the lizard had no abdominal fat bodies the animal was still in a reproductive state, indicating that it was not only able to regenerate a tail twice, but it could also still meet the energetic demands for reproduction.

This finding prompted our study to attempt to address the question of whether there are differences in the abdominal fat body weights and liver weights of A. sagrei specimens that had suffered tail autonomy and conspecifics that had not.

We were surprised when we found no statistically significant variations in the monthly mean abdominal fat-body weight indices or monthly mean liver weight indexes of lizards that had not experienced caudal autotomy and those that had. We hypothesize that A. sagrei specimens that experienced tail autotomy most likely met the energetic demands for regenerating the lost portion of their tail by foraging more.

Editor’s Note: for more on two-tailed anoles, such as the photo below, type “tail” or “tailed” into the search bar on the right.

The uninformed often view parasites with disdain, disgust, and/or condemnation. These views however ignore the various ecological roles that parasites play. My colleagues and I are some of the lucky few who look at these organisms through ecological lenses and marvel at what we find.

An Anolis sagrei male from Chiayi County, southwestern Taiwan.

As part of the ongoing research on the exotic invasive brown anole (Anolis sagrei) populations in Taiwan, we collected and examined some specimens for parasites. In addition to the brown anoles, we also examined specimens of Eutropis longicaudata, Eutropis multifasciata, Japalura polygonata xanthostoma, Japalura swinhonis, Plestiodon elegans, and Sphenomorphus indicus, that were collected opportunistically from Taiwan.

We recently reported on the parasites we recorded in 52 of the 91 lizards examined, and the infected individuals harbored one to three species of parasites. We identified the parasites as Cyrtosomum penneri, Kiricephalus pattoni, Mesocoelium sociale, Meteterakis govindi, Oochoristica chinensis, Oswaldocruzia japalurae, Parapharyngodon maplestonei, Pseudabbreviata yambarensis, Pseudoacanthocephalus bufonis, or Strongyluris calotis. We also recorded an unidentifiable acanthocephalan infective juvenile (cystacanth) and an unidentifiable larva of a cestode (sparganum).

Based on the relatively few parasite species recorded from A. sagrei in Taiwan, compared to the large number of parasites reported from A. sagrei throughout its native and introduced range, it is clear that these lizards have been liberated from many of their parasites.

The nematode, Cyrtosomum penneri, which was introduced into Taiwan along with A. sagrei, was a common parasite in the A. sagrei we examined. None were recorded in any of the other lizard species examined. This is most likely because these nematodes are transmitted from one host to another during copulation and appears to have a fair degree of host specificity, so the spread of C. penneri to native lizard species in Taiwan is suggested to be very unlikely. An interesting conclusion that can be drawn from the presence of C. penneri in specimens from both the southwestern and eastern populations of A. sagrei in Taiwan is that sexually mature lizards were introduced into these localities and that they most likely have a common founder population.

Our study did also confirm that the digenean, Mesocoelium sociale, and the pentastome, Kiricephalus pattoni are acquired parasite of A. sagrei in Taiwan. Unfortunately, although their infections can be expected to be detrimental to the A. sagrei host, their infection frequencies are relatively low in the A. sagrei populations in Taiwan, and thus have no observed significant impact on the population sizes.

Another interesting finding of our study was that even though the nematodes, Pseudabbreviata yambarensis and Strongyluris calotis, are very common in Japalura swinhonis, a species that is very often sympatric with A. sagrei in Taiwan and which also has a very similar diet as A. sagrei, they have not been found in any of the A. sagrei examined to date. This could be a result of an absence of transmission routes that could be specific to J. swinhonis and thus protect introduced species from the native parasites, or the host-specific limitations of the parasites prevent them from adapting to a new hosts, i.e., A. sagrei.

I would like to encourage everyone involved with research to include parasitological studies in their herpetological works to expand our understanding of host-parasite ecology.