Do invasive house geckos exacerbate dengue fever epidemics?

Dengue fever is a mosquito-borne disease that has undergone a marked rise in incidence since the 1950s, throughout the world’s tropical regions. Here, we present a hypothesis that this rise in incidence may have been exacerbated by the invasion of house geckos, due to their role in the mosquito vector food web. Previous research has shown that in the absence of a top predator, house geckos reach high densities, directly affecting spider densities and indirectly resulting in higher Aedes-mosquito densities. Hence, we expect that in areas where house geckos are invasive and an effective top predator is lacking, Aedes densities will be higher, resulting in a higher dengue fever incidence rate. We perform a preliminary test of this hypothesis by looking for patterns in secondary country-level data to estimate the global range of invasive house gecko species over time. We related these estimated ranges to variation in the number of per capita dengue cases in 80 different countries. The incidence of dengue was significantly higher in countries where house geckos were introduced, when compared with countries where it was either native or absent. In addition, in countries where house geckos were introduced earlier and had time to become naturalized, dengue fever incidence rates were higher than for countries where house geckos were introduced more recently. These results suggest that house geckos could indeed have played a role in the rise of dengue in tropical countries. Here, we present a framework for the required experimental research to test the mechanism underlying these observations.

The complete study can be found under the following link:

Dengue vector food webs: geckos, spiders and mosquitoes

Effective management of mosquito-borne diseases, such as dengue fever, requires that we understand how human modifications of the landscape affect mosquito populations. Increased mosquito populations may result from changes in predator community composition caused by habitat modification. We tested for this effect at a regional scale by investigating how landscape context affects both terrestrial and aquatic mosquito food-webs in 70 sites across northwestern Thailand. Landscape context strongly affected mosquito-predator communities in both the aquatic and terrestrial environment via cascading food-web interactions. Several components of these food-webs that could be manipulated for conservation biocontrol, such as house-dwelling spiders and geckos, were strongly affected by landscape context and played an important role in regulating the mosquito population. In the terrestrial food-web, the habitat-sensitive tokay gecko was critical in structuring mosquito predator communities showing that a conservation approach to vector control could be a useful addition to existing control efforts.

The complete study can be found under the following link:


Figure on top: The large tokay gecko was found to feed on smaller house geckos (Hemidactylus spp.), which caused an increase in spiders due to reduced predation. Subsequently this resulted in less Aedes mosquitoes. In forest habitats Tokay geckos were more common in comparison to urban habitats. Tokay absence contributed to increased mosquito densities in urban areas.

How the landscape affects aquatic mosquito predators

Various studies have shown that the prevalence of mosquito borne diseases such as malaria and dengue fever is correlated to deforestation and urbanization. Some factors that can explain such a correlation are, for example, changes in micro-climatic conditions that come with such changes in the landscape but also the availability of breeding habitats for mosquitoes. We wondered if effects on the landscape scale would also affect predator prey interactions. Different species may be affected by landscapes in different ways and it is therefore likely that a correlation between such changes and the abundance of vector mosquitoes could result from changes in predator-prey interactions.

Hence, we conducted a field experiment in which we placed water-filled containers in trees along a gradient of forest and urban habitats and monitored the dengue vectors and predators that colonized these containers. We found that aquatic predators more quickly colonized containers in landscapes that contained more green spaces (think of forests but also urban parks). In addition, the distance to large aquatic habitats also had a major effect on the colonization rate of predators. In containers that were colonized with predators the mosquito densities were much lower.

We can conclude that in urban areas mosquitoes prevail due to a decreased colonization rate of predators, which may be another underlaying factor that helps explaining the relationship between deforestation, urbanization and dengue fever.

You can read more about this study here.

Invasive mosquito predators: the distribution of house geckos

House gecko are common predators of dengue vectors that can be found in many houses in the tropics. Several species occur in Thai homes of which the most common species are the Asian house gecko (Hemidactylus frenatus) and the flat-tailed house gecko (H. platyurus). Hemidactylus species can be found in many parts of the world. During the last few centuries global trade has facilitated their spread, and now they have invaded many parts of the world where they are considered invasive species. In these new regions they often have negative  effects on the local herpetofauna through competition and the spread of parasites and diseases.

In context of mosquito control it may be very useful to understand the distribution of these species and the regions to which they can potentially expand their range. Therefore, we collected secondary species occurrence data from various sources and mapped the current and potential range of five of the most common invasive Hemidactylus species. We found that the Asian house gecko is very common outside its native range, especially in Central America and Australia. The Brook’s house gecko is even more commonly found outside its native range and is very likely to even further expand its range in the future. How this will affect ‘natural’ mosquito control remains unclear. Therefore, investigating the role of these invasive species in the control of mosquitoes will be an important aspect of our future work.

Please follow this link, if you would like to read the complete study.

Are geckos the new mice?

In some species of geckos that live in buildings or other human-modified locations, it has been observed that they opportunistically feed on insects that are attracted by artificial lights. Such observations have also been reported for G. gecko and G. monarchus. To date only two unpublished studies have focused on foraging behaviour and diet of G. monarchus. The first study focused on spatial partitioning around artificial lights and found no inter-specific differences among four gecko species. While the other study showed that the diet of G. monarchus consists mostly of termites (Isoptera), wasps and sawflies (Hymenoptera), true flies (Diptera) and spiders (Arachnidaea). Based on the scarce information available for this species, G. monarchus was to date considered a strict insectivore. We recently observed G. monarchus feeding on non-insect food items. On 7 July 2017 between 20:30 PM and 21:00 PM, in Tanjung Selor, North Kalimantan, Indonesia (2.8366°N, 117.3724°E), we observed two individuals feeding on white bread on a table in a kitchen… more

The full report can be found here.

Opportunistic feeding in flat-tailed house geckos

House geckos (Hemidactylus spp.) are voracious insectivorous that feed on large numbers of insects daily. Several species of this genus live inside buildings in close proximity to people where they forage near artificial lights, feeding on those insects that are attracted to light. This makes these species excellent subjects for behavioral studies and dietary analysis. Indeed, many studies have investigated the diets of geckos belonging to the genus Hemidactylus and found that diets of these species mainly consist of insects such as Lepidoptera, Diptera but often also contain other arthropods such as Arachinidae. Most of these studies suggest that house geckos are strict insectivores, which is not any different for the flat-tailed house gecko (Hemidactylus platyurus).

During the period between March 2013 to December 2016, I often observed house geckos (both Hemidactylus frenatus and H. platyurus) foraging in garbage-bins and on diner-tables in Kamphaeng Phet and Minburi, Thailand and Malinau, Indonesia… more

To full report is freely accessible and can be found here.

The diets of bats – What about mosquitoes?

Bats are voracious insectivores and may potentially play a role in the control of vector mosquitoes. We analyzed the diets of five bat species in central Thailand and found considerable amounts of mosquitoes in the feces of bats from an urban colony of Taphozous longimanus. Previous studies have shown that bats can have a substantial impact on the abundance of mosquitoes (Reiskind and Wund 2009). However, our field data (unpublished) showed also that there was no correlation between bat feeding activity and Aedes mosquito prevalence. A lack of this correlation could possible be explained by the diurnal character of Aedes mosquitoes. Hence, bats may possibly be more important for the control of nocturnal mosquito species such as Anopheles species which can transmit malaria and Culex species which can transmit the West Nile virus.

You can read more about the diets of bats from central Thailand here.


Reiskind MH & Wund MA (2009) Experimental assessment of the impacts of northern long-eared bats on ovipositing Culex (Diptera: Culicidae) Mosquitoes. Journal of Medical Entomology, 46: 1037–1044.

Tadpoles: Do they really eat mosquito larvae?

Tadpoles are often considered to be important predators of mosquito larvae. Hence, we experimentally investigated the predation potential of three different frog species that are common in central Thailand. Unlike generally assumed the tadpoles in our study did not feed on mosquito larvae at all. In fact tadpoles of most frog species do not feed on mosquito larvae, only few species do. But this does not mean that tadpoles do not play a role in the control of mosquitoes at all. Some of the species we studied have been shown to feed on mosquito eggs (Bowatte et al. 2013) and tadpoles are also known to compete for food with mosquito larvae (Mokany and Shine 2003). Such negative effects were also observed in central Thailand (unpublished), where we observed a strong negative correlation between tadpole abundance and mosquito larvae presence.

You can find the complete results of our tadpole-mosquito predation experiment here.


Bowatte, G., P. Perera, G. Senevirathne, S. Meegaskumbura, and M. Meegaskumbura. 2013. Tadpoles as dengue mosquito (Aedes aegypti) egg predators. Biol. Contr. 67: 469-474.

Mokany, A. and R. Shine. 2003. Competition between tadpoles and mosquito larvae. Oecologia 135: 615–620.

Dragons and damsels; mosquitoes in distress

Aquatic predators can have a profound impact on the abundance of mosquito larvae. Such predators can include fish such as guppies but also aquatic insects such as backswimmers (Notonectidae) and dragonfly naiads (larvae). We conducted several experiments focusing on various aspects of the predatory behaviour of aquatic insects. One group of insects that we looked at were dragonfly and damselfly naiads (Odonata). We assessed predation rates as an effect of mosquito larvae densities, predator densities and predator size.

We found that predator density had a negative effect on the rates at which individual predators consumed mosquito larvae, but with increasing numbers of predators the total amount of mosquito consumed did increase. However, after a certain threshold of predator densities the total number of mosquitoes consumed decreased. As densities increase the naiads likely experienced a higher threat from conspecifics, because they do like to eat each other as well. While hiding for their neighboring naiads the mosquitoes larvae had a better chance of surviving.

Dragonfly and damselfly naiads appear to be effective predators of mosquito larvae. Although naiads occur in different aquatic habitats than Aedes larvae, they do often co-occur in nature with other vector mosquito species such as Anopheles (Malaria) and Culex (West Nile Virus).

You can find more about this study here.

What do geckos like for diner?

One predator of mosquitoes that is often found inside houses in the tropics are the house geckos. House geckos can be found in all colors and sizes and you can see them often feeding on insects that are attracted to lights. During the day they often hide in dark places, where mosquitoes often hide as well. To find out what impact house geckos have on mosquitoes inside these houses it is important to better understand their feeding behavior.

Together with two students from the University of Applied Sciences Van Hall Larenstein we investigated the feeding behavior of two common house geckos in central Thailand: the Asian house gecko (Hemidactylus frenatus) and the flat-tailed house gecko (H. platyurus). We observed house geckos while feeding and counted the attack rate on various prey and estimated the effort for each attack as the total distance walked towards a prey. The results showed that house geckos prefer moths (Lepidoptera) over any other kind of insect. In addition, house gecko invested slightly more energy in attacks on mosquitoes than on insects from different orders. This slight preference for mosquitoes can possibly be explained by the fact that mosquitoes are soft bodied and are easily digested in contrast to for example beetles which have a hard exoskeleton.

Previous experimental studies have also shown that house geckos can feed on very high number of mosquitoes (Canyon and Hii 1997). However, what the effect of house geckos is on the natural control of mosquitoes in and around our houses remains unclear, but we are working hard to figure that out

You can find the results from the complete study here.


Canyon, D.V., Hii, J.L.K. (1997): The gecko: an environmentally friendly biological agent for mosquito control. Medical and Veterinary Entomology 11: 319–323.