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Prey preference of the Common House Geckos Hemidactylus frenatus and Hemidactylus platyurus


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House geckos (Hemidactylus frenatus and H. platyurus) are very common in residential areas throughout Southeast Asia. Geckos are fierce insect feeders and their role in in-home pest control is worth considering. Here a study is presented that aims to elucidate the prey choice behaviour of both gecko species. We observed wall dwelling house geckos that foraged near artificial lights in Thailand. The invested effort for each attack sequence was compared to the estimated prey size and the prey type. We found that the house geckos fed most on Diptera. However, they showed a strong preference for Lepidoptera and a slight preference for Culicidae. These results are further discussed in the context of the optimal foraging theory.
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House geckos are common throughout the tropics,
with some species being very well adapted to living
in urban environments (Vanderduys and Kutt, 2012).
The common house gecko, Hemidactylus frenatus
Schlegel 1836, is a species that is native to Southeast
Asia, but nowadays can be found in many other regions
of the world as an invasive species (Hoskin, 2011).
Hemidactylus frenatus is often found inside buildings
feeding on insects that are considered to be pests
(Tyler, 1961; Newbery and Jones, 2007). The foraging
behaviour of H. frenatus has previously been studied
under experimental conditions by Canyon et al. (1997).
These authors studied the predation rate of H. frenatus
and the gecko Gehyra dubia (Macleay, 1877) feeding
on mosquitoes. Predation rates were relatively high (63
to 109 mosquitoes per day depending on prey density)
in comparison to other in-home wall-dwelling mosquito
predators such as daddy long leg spiders (Crosspriza
lyoni) (Strickman et al., 1997) or jumping spiders
(Salticidae) (Weterings et al., 2014). Dietary analyses
based on stomach contents have shown that the diet of
H. frenatus is very diverse (Tyler, 1961; Diaz Perez et al.,
2012). Based on these results H. frenatus is considered
to be an opportunistic generalist predator. However,
dietary content by itself does not give any information
with regard to prey preference.
House geckos might be considered as a pest
themselves. Their faeces are often considered to be
a nuisance and can even cause salmonella infection
when ingested (Bockemuhl and Moldenhauer, 1970;
Callaway et al., 2011). Nevertheless, the role of geckos
in pest control might still be considered to be very
benecial (Canyon and Hii, 1997). Mosquitoes seem to
constitute a major part of the diet of this very common
species (Tyler, 1961; Newbery and Jones, 2007). From
a biocontrol perspective it is thus of great interest to
understand the feeding behaviour of common house
geckos in more detail. In order to assess whether house
geckos are suitable for biological control, it is important
to understand its diet, in particular the preference for
certain prey (Berryman, 1999). Here we present an
observational study of prey preference in H. frenatus
and Hemidactylus Platyurus (Schneider, 1792), two
common house geckos that can be found throughout
Southeast Asia.
Herpetology Notes, volume 7: 483-488 (2014) (published online on 25 August 2014)
Prey preference of the Common House Geckos
Hemidactylus frenatus and Hemidactylus platyurus
Gwendola K. Tkaczenko
, Adeline C. Fischer
and Robbie Weterings
Department of Animal Management, VHL University of
Applied Science, Agora 1, 8934 CJ Leeuwarden, The
Cat Drop Foundation, Boorn 45, 9204 AZ, Drachten, the
Faculty of Agriculture Natural Resources and Environment,
Naresuan University, 99 Moo 9 Phitsanulok-Nakhonsawan
Road Tambon Tapho, Muang Phitsanulok, 65000 Thailand.
* Corresponding author; email:
Abstract. House geckos (Hemidactylus frenatus and H. platyurus) are very common in residential areas throughout Southeast
Asia. Geckos are erce insect feeders and their role in in-home pest control is worth considering. Here a study is presented that
aims to elucidate the prey choice behaviour of both gecko species. We observed wall dwelling house geckos that foraged near
articial lights in Thailand. The invested effort for each attack sequence was compared to the estimated prey size and the prey
type. We found that the house geckos fed most on Diptera. However, they showed a strong preference for Lepidoptera and a
slight preference for Culicidae. These results are further discussed in the context of the optimal foraging theory.
Key Words: Hemidactylus frenatus; Hemidactylus platyurus; Diet; Food preference; Prey choice.
Gwendola K. Tkaczenko et al.
Materials and Methods
Behavioural observations
During a period of three months (November 2013
to January 2014) we observed geckos on buildings
in Muang Kamphaeng Phet, Thailand. Geckos were
studied from approximately 19:00 to 21:00 for a total
of 34 nights. Observations were made on walls and
ceilings of inhabited buildings that were provided
with articial lights. We used binoculars to observe the
geckos in order to increase the distance and reduce the
interference with their natural hunting behaviour. Each
night we observed multiple geckos on a single wall. We
noted the gecko species (H. frenatus or H. platyurus),
the order (and the dipteran family Culicidae) to which a
prey insect belonged, the approximate size of the prey,
and the approximate distance that a gecko moved to
catch a prey. Prey insects that could not be identied
were noted as unknown. Size of prey insects could not be
measured directly because this would interfere with the
attack sequence. Therefore we estimated the size of prey
by assigning it to one of the following six categories:
0-4 mm, 5-9 mm, 10-19 mm, 20-29 mm, 30-39 mm and
greater than 39 mm. The attack distance, the distance
moved into the direction of a certain prey, could also
not be measured directly. Distance was categorized into
4 different categories. The rst category contained the
shortest distance and thus the least effort which consisted
of only a slight movement of the head and/or tongue.
The second category consisted of an attack sequence
in which the gecko performed a small jump towards its
prey; this category did not involve any walking. In the
third and fourth category the geckos stalked their prey
and walked either a distance of less than 25 cm or more
than 25 cm.
Insect sampling
To assess the presence of insects we placed one sticky
trap in front of the wall at each sampling location.
The sticky traps were placed 20 minutes prior to
the behavioural observations and removed after we
nished observing the geckos. The single-sided surface
(15cm by 30cm) of the sticky traps was covered with
a layer of weather proof glue, consisting of a rubber
based adhesive mixed with an organic solvent. After
collecting the insects the sticky traps were sprayed with
permethrin, a pesticide, to kill all insects. The sticky
trap was then placed into a plastic box to protect the
insects from external inuences during transportation.
All insects apart from mosquitoes were identied to the
order level; mosquitoes were identied to the family
We used a Chi squared test of independence to test
for differences between the observed number of prey
in certain orders, and the number of insects that were
present on the sticky traps. We assessed the adjusted
residuals to see if there was a difference in the ratio of
prey consumed from certain orders in comparison to the
insects that were present. We considered an absolute
adjusted residual (a.r.) value of two or higher to be
different (Agresti, 2007). For this analysis we only used
the data for the samples for which the insect community
was considered similar according to another Chi squared
test (nine nights). We also used the Chi squared test of
independence to assess differences in prey preference
among the two focal species and to assess the size
classes for each insect order.
The effect of gecko species, insect order and insect size
on hunting effort was assessed using a Cumulative Link
Mixed Model (CLMM). This type of model allowed us to
use an ordinal response variable in a regressional fashion
(Christensen, 2012). We used the movement distance as
our ordinal response variable and the insect order, insect
size and gecko species as independent variables. Data
violated the assumption of independence: data were
clustered on different sites (34). To account for the
clustering of the data we added location as a random
effect to the models. We used the model inference
approach described by Anderson (2008) to select the
best model. Following this approach we developed a
priori hypotheses that were all represented in different
models. Subsequently these models were compared
using the AICc score (Anderson, 2008). We calculated
model weights in order to develop an averaged model
based on all a priori hypothesized models. All analyses
were conducted in RStudio (RStudio, 2012) built on R
3.0.0 (R Development Core Team, 2013). The ‘ordinal’
package (Christensen, 2012) was used to conduct the
CLMM analysis.
A total of 1034 attacks were observed, 523 for H.
frenatus and 511 for H. platyurus. Most preyed insects
belonged to the orders Diptera (36.3%) and Homoptera
Prey preference of Hemidactylus frenatus and Hemidactylus platyurus
Table 1. Number of insects preyed by H. frenatus and H. platyurus as frequency and percentage. The
numbers of insects on the sticky traps and the total availability of insects (preyed plus sticky traps) are
also included.
Prey type H. frenatus H. platyurus Sticky trap Total availability
3.8 %
0.9 %
30.4 %
6.0 %
35.4 %
5.4 %
0.1 %
0.2 %
0.1 %
2.6 %
2.2 %
32.8 %
3.5 %
31.7 %
5.7 %
0.1 %
3.1 %
0.4 %
17.9 %
Table 1. Number of insects preyed by H. frenatus and H. platyurus as frequency and percentage. The numbers of insects on the
sticky traps and the total availability of insects (preyed plus sticky traps) are also included.
Table 2. Comparison of models that looked at hunting effort. The 'order' resembles the taxonomic
insect orders, 'size' is the size category of a prey and 'gecko species' is the focal species. d.f are the
degrees of freedom, AICc is the corrected Aikake's Information Criterion, ǻ is the difference in AIC
score in comparison with the best model and W
is the model weight (selection probability).
Parameters d.f. AIC
ǻ W
order + size
order + size + gecko species
order + gecko species
size + gecko species
gecko species
Table 2. Comparison of models that looked at hunting effort. The ‘order’ resembles the taxonomic insect orders, size is the
size category of a prey and ‘gecko species’ is the focal species. d.f are the degrees of freedom, AICc is the corrected Aikake’s
Information Criterion, Δ is the difference in AIC
score in comparison with the best model and W
is the model weight (selection
Figure 1. The hunting effort is displayed as the percentage in each class per insect order. For insect orders on the right of the
graph the effort to catch a prey is lowest for insect orders on the left the effort is highest. N is the number of observed attacks of
prey within each order.
(26.4%) (Table 1). The insects (n=1492) caught on the
sticky traps belonged to eight orders of which six also
occurred in the diets of H. frenatus and H. platyurus. The
Chi squared test did not show any signicant differences
in diets between the two gecko species (X
= 13.65, d.f.
= 7, p-value = 0.06). The Chi squared test that compared
diet versus the insects that were available showed that
there was a signicant difference (X
= 96.25, d.f. =
7, p-value < 0.001). Both species appeared to prefer
Lepidoptera (a.r = 5.3), Diptera (a.r = 3.4), Culicidae
(a.r = 2.8), Neuroptera (a.r = 2.6), Hymenoptera (a.r =
2.2) and avoided Heteroptera (a.r = -4.6) and Coleoptera
(a.r = -3.4). All other insect orders did not differ in the
ratio in which they appeared in the diet versus the sticky
The CLMMs showed that insect order and insect
size were important factors in the effort that was put
into an attack sequence (Table 2). For larger prey the
attack distance was highest (Figure 1) as well as for
Lepidoptera, Hymenoptera and Culicidae respectively
(Figure 2, Table 3). Insects of the order Lepidoptera and
Hymenoptera were generally larger than expected, while
Culicidae were generally smaller but did not differ from
the expected values (X
= 982.55 , d.f. = 35, p-value <
0.001, see Table 4 for the adjusted residuals).
Table 3. Parameter estimates for the best model. The categories Coleoptera (insect order) and 0-4mm
(prey size) are included in the threshold coefficients. In the threshold coefficients 0 represents the
category with the lowest hunting effort and 3 the category with the highest effort.
Coefficients Estimate (SE)
Threshold coefficients
insect orders
40mm or greater
0.09 (0.70)
2.31 (0.70)
3.83 (0.71)
-0.02 (0.68)
-0.06 (0.69)
0.09 (0.69)
0.23 (1.02)
0.75 (0.73)
1.30 (0.76)
3.25 (0.78)
0.99 (0.18)
1.21 (0.36)
0.74 (0.55)
3.17 (1.24)
4.20 (1.18)
Figure 2. The hunting effort is displayed as the percentage in each class per insect size. For small insects on the right of the graph
the effort to catch a prey is lowest for large insects on the left the effort is highest. N is the number of attacks in each size class.
Table 3. Parameter estimates for the best model. The categories
Coleoptera (insect order) and 0-4mm (prey size) are included
in the threshold coefcients. In the threshold coefcients 0
represents the category with the lowest hunting effort and 3
the category with the highest effort.
Gwendola K. Tkaczenko et al.
Our results clearly displayed that both focal species
do not randomly select their prey. Prey items were
generally larger than expected from a random selection.
Lepidoptera tended to be preferred by H. frenatus
and H. platyurus. There appeared to be a disfavour
for Heteroptera and Coleoptera. Both gecko species
showed a slight preference towards Culicidae which
was reected in both the prey choice and attack distance.
Lepidoptera and Culicidae are generally much softer than
Heteroptera and Coleoptera (Hackman, 1974; Evans and
Sanson, 2005). Softer insects are easier to digest and
apart from size this might have inuenced a preference
towards these insects, especially considering the fact
that Culicidae are not specically large in comparison
to the other insects that were encountered. The optimal
foraging theory suggests that an individual of any
species aims to retrieve most energy while investing the
least energy (Stephens and Krebs, 1986). Some basic
predictions based on this theory are that an individual
would put more energy in hunting a large prey in
comparison to a small prey (Stephens and Krebs, 1986).
In addition an individual would prefer an easy digestible
prey over a hard to digest prey because this will cost less
energy (Stephens and Krebs, 1986). Many insectivorous
vertebrate species are known to choose their prey based
on cuticle thickness or ‘hardness (Fisher and Dickman,
1993; Weterings and Umponstira, 2014). Our results
suggest that H. frenatus and H. platyurus both forage
Previous studies regarding the diet of H. frenatus
showed varying results. Tyler (1961) reported that the
diet of the latter was mainly comprised of Diptera,
Lepidoptera and Coleoptera while Diaz-Perez et al.
(2012) reported a diet that comprised of Hemiptera,
Hymenoptera and Coleoptera. These large differences
in diets might be explained by the availability of prey
which can show strong spatial and temporal variation.
Also in our study area we can see large temporal
variation in insect abundance. For example during the
onset of the rainy season, termite alates (Isoptera) and
ant alates (Hymenoptera: Formicidae) swarm in large
numbers when the rst rain has fallen after a long period
of drought (Lepage and Darlington, 2000). House
geckos can then be observed feeding ferociously on
the alates (personal observations). This opportunistic
feeding on alates has also been observed for other
lizards in Thailand (Schaedla, 2004).
Previous studies have suggested that mosquito
predation by H. frenatus is of considerable importance
(Tyler, 1961; Canyon and Hii, 1997; Newbery and Jones,
2007). Based on our observations we can conclude that
house geckos show potential as a mosquito control
measure. Nevertheless, this is very dependent on the
composition of the overall in-home prey community.
Acknowledgements. We would like to thank Asst. Prof. Dr.
Chanin Umponstira and his staff from the Faculty of Agriculture
Natural Resources and Environment, Naresuan University, for
supplying some of the materials. We also would like to thank
Berend van Wijk, Hans Bezuijen, Henry Kuipers and Martijn
van der Ende (VHL University of Applied Science) for feedback,
materials and other forms of support during the process of this
project. Our gratitude goes out to Julie Dobson for proof reading
an early version of the manuscript and to ‘Skills for Change’ for
providing micro-volunteers.
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Prey preference of Hemidactylus frenatus and Hemidactylus platyurus
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Accepted by Zoltán Nagy;
Managing Editor: Wouter Beukema
Gwendola K. Tkaczenko et al.
... Hemidactylus frenatus and Gehyra mutilata) are often found in and around houses. These, so-called 'house' geckos, are very well adapted to urban life and are often observed feeding opportunistically on insects attracted to artificial lights at night (Tkaczenko et al., 2014). This provides them an easily accessible food source in locations generally lacking predators. ...
... There have been several dietary studies of house geckos including H. frenatus, H. mabouia, H. platyurus, G mutilata and H. turcicus (Tyler, 1961;Saenz, 1996;Ramires & Fraguas, 2004;Rocha & Anjos, 2007;Diaz Perez et al., 2012;Tkaczenko ...
... Feeding behaviours by house-dwelling geckos et al., 2014;Barragán-Ramírez et al., 2015). In most of these studies, only insects were found in the diet although a few mention the presence of vegetal items within the stomach content (Iturriaga & Marrero 2013;Barragán-Ramírez et al., 2015). ...
Various species of ‘house’ gecko are found in and around buildings, where they can be observed feeding opportunistically on the insects attracted to artificial lights. Most of the species are considered strict insectivores. Nevertheless, there have been several recently published observations of ‘house’ geckos feeding on non-insect food. In order to assess how common this behaviour is among geckos worldwide, we offered an online questionnaire to ecologists and herpetologists. Of the 74 observations received, most reported Hemidactylus frenatus, H. platyurus and Gehyra mutilata feeding on rice, bread, fruits, vegetables, dog food or chocolate cream, taken from tables, plates, and garbage bins. This opportunistic feeding behaviour is much more common than previously thought and is perpetrated by species considered to be highly invasive, possibly contributing to their success as invaders.
... Breeding data were noted as egg number, incubation period, precloacal pores and female size. We also collected information on habits, habitats and life history patterns of Hemidactylus which includes direct observation, morphometric studies, gut analysis and sampling (Zug et al. 2007, Naher et al. 2013, Tkaczenko et al. 2014, Hasan et al. 2014. The data were analyzed employing statistical package R-3.5.1 and Pearson correlation coefficient of different parameters was calculated. ...
... Hasan et al. (2014) suggest that all are commensalistic and nocturnal in habit. Tyler 1961, Zug et al. 2007, Chakma 2009, Hoskin 2011, Naher et al. 2013, Hasan et al. 2014Zug et al. 2007, Chakma 2009, Hasan et al. 2014, IUCN BD 2015Zug et al. 2007, Chakma 2009, Hasan et al. 2014, Tkaczenko et al. 2014, IUCN BD 2015 Notes: A= Araneae, C= Coleoptera, D= Diptera, H= Homoptera, He= Hemiptera, Hy= Hymenoptera, I= Isoptera, L= Lepidoptera, O= Orthoptera, Z= Zygoptera ...
... H. frenatus used to eat dipterans (Tyler 1961) and coleopterans (Naher et al. 2013) mostly as their food. The feeding ecology and habitat of H. platyurus and H. frenatus was studied by Tkaczenko et al. (2014) through behavioral observation and insect sampling revealing preference of insects of the order of Araneae, Coleoptera, Diptera, Homoptera, Hymenoptera, Lepidoptera, and Orthoptera. It reflects similarity with the behavior of H. brookii and H. flaviviridis studied by Chakma 2009 (Table 2). ...
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Hemidactylus is a taxonomically complex genus and little is known about its feeding and breeding behavior in Bangladesh. Most of the species of this genus have a preference to live within human habitations, and play an important role in ecosystem, controlling insect pest population. Their breeding strategy is almost similar with each other and associated with their body structure. Review of literature found that there is a relationship between life history pattern and their reproductive biology. They lay two eggs per clutch usually and the highest egg number (12) has been recorded for H. frenatus. Strong significant positive correlation (r = 0.91) was found for preclaocal-femoral pores and egg number. Besides, significant negative correlation was found for average female body size and egg number (r = 0.96). Previous work and observation records showed that feeding habit is almost similar among all species of Hemidactylus and dipteran insects were the mostly consumed food item. J. Biodivers. Conserv. Bioresour. Manag. 2019, 5(1): 77-84
... Among the reptile species, wild geckos are widely distributing in residential areas in Southeast Asian countries (Tkaczenko et al., 2014), and they can excrete their faeces in the environment. ...
... In other reports, S. Weltevreden was also the most predominant Bovismorficans and Newport serovars isolated from wild geckos in the Mekong Delta were also isolated from human diarrhoea patients in this region (Ly et al., 2010). In Southeast Asian countries, wild geckos have been prevalent widely and close contact with human (Tkaczenko et al., 2014); moreover, wild geckos can excrete a high number of Salmonella, which can survive for 6 weeks in their faeces (Nguyen et al., 2018). Those geckos can drop faeces and cause contaminated Salmonella in foods, water, etc., which people use or consume it. ...
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A total of 1,318 wild geckos were collected in Cambodia, Thailand and Vietnam (Hue and the Mekong Delta) from 2012 to 2015 to determine the prevalence of Salmonella Weltevreden. Those geckos belong to three species: common house gecko (Hemidactylus frenatus), flat‐tailed house gecko (Hemidactylus platyurus) and four‐clawed gecko (Gehyra mutilata). Of 1,318 gecko samples, 293 (22.2%) samples were positive for Salmonella in this study. The prevalence of Salmonella in geckos was 46.0% in Thailand, 17.3% in Cambodia and 16.3% in Vietnam. Among the Salmonella isolates, S. Weltevreden was the most predominant serovar (32.1%) isolated from wild geckos in these countries. There was no significant difference in the prevalence of Salmonella among gecko species. All S. Weltevreden isolates (100%) were susceptible to the nine antibiotics examined in this study. The PFGE assay by XbaI enzyme identified 19 different patterns from 75 S. Weltevreden isolates. These isolates showed high genetic heterogenicity, and there were specific types prevalent in each region. Furthermore, S. Weltevreden has been prevalent since the ancient times in this region. The results indicate that wild gecko seems to be an important natural reservoir for S. Weltevreden as well as a source of Salmonella infections in humans in Southeast Asian countries.
... Predators with high predation rates on mosquito larvae and pupae include fish 10,11 , odonate young instars 12 , other mosquito species 13 , amphibians 14 , and copepods 15 . Although attention was mainly given to mosquito pre-imago stage predation, recent studies demonstrated that predators of adult mosquitoes, such as spiders and geckos, have a high potential to reduce mosquito populations [16][17][18][19][20] . Adult mosquito predators also include bats 21 , dragon flies 22 , frogs 23 , birds 24 . ...
... In general, the food web of geckos and mantises includes various species of insects including mosquitoes. Many studies carried out on house gecko feeding behavior, Hemidactylus frenatus and H. platyurus, showed that they feed mostly on Diptera with a preference for Lepidoptera and Culicidae 18,58,59 . However, literature research about the day geckos P. standingi and P. laticauda predation on mosquitoes was not found. ...
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The sterile insect technique is a promising environmentally friendly method for mosquito control. This technique involves releasing laboratory-produced sterile males into a target field site, and its effectiveness may be affected by the extent of adult mosquito predation. Sterile males undergo several treatments. Therefore, it is vital to understand which treatments are essential in minimizing risks to predation once released. The present study investigates the predation propensity of four mantis species (Phyllocrania paradoxa, Hymenopus coronatus, Blepharopsis mendica, Deroplatys desiccata) and two gecko species (Phelsuma standingi, P. laticauda) on adult Aedes aegypti, Ae. albopictus and Anopheles arabiensis mosquitoes in a laboratory setting. First, any inherent predation preferences regarding mosquito species and sex were evaluated. Subsequently, the effects of chilling, marking, and irradiation, on predation rates were assessed. The selected predators effectively preyed on all mosquito species regardless of the treatment. Predation propensity varied over days for the same individuals and between predator individuals. Overall, there was no impact of laboratory treatments of sterile males on the relative risk of predation by the test predators, unless purposely exposed to double the required sterilizing irradiation dose. Further investigations on standardized predation trials may lead to additional quality control tools for irradiated mosquitoes.
... This species has a wide range of distribution including India, Southeast Asia, to Australia. The successful distribution of this species is due to human intervention, as well as the high adaptability of this species both from a physiological perspective such as food dynamics, reproduction time, and camouflage that allows this species to adapt to its environment and avoid predators (Carranza and Arnold, 2006;Tkaczenko et al., 2014;Bansal and Karanth, 2010). ...
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Common house gecko (Cosymbotus platyurus) is the most abundant house gecko species in Indonesia. The geckos live in home yard, garden, and in homes. It is part of food chain in its habitat, as its preys include cockroaches, flies, and termites. Previous studies found that this gecko are not found in mountainous area in West Java. In this study, the researchers observe population density of common house geckos in various types of habitats (houses and parks) with their home territory. The methods used were direct survey methods followed by literature study. The study is conducted in Java island (Jakarta, Tangerang, Bandung, Bogor, Sleman). Preliminary result of this study is house geckos are very active at night, because of the effect of light produced by lights that attract the attention of insects, gecko food.
... Philippine gekkonids are mostly arboreal, ground, and rock dwellers, with a few species demonstrating extraordinary commensal behavior living in close association with humans (Parves and Alam 2015). Mostly nocturnal, they feed on insects and small arthropods and play a vital role in pest control (Newbery and Jones 2007;Tkaczenko et al. 2014;Meiri 2019). They inhabit a range of environments from builtup areas, mixed agricultural plantations, and lowland forests (Siler et al. 2012;Sanguila et al. 2016;Supsup et al. 2016Supsup et al. , 2020. ...
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This study highlights the ecology, natural history, and a new distribution record by providing a unique habitat occurrence record in karst ecosystem and describes a tail anomaly of the endemic Mamanwa Bent-toed Gecko Cyrtodactylus mamanwa in the province of Dinagat. The detection of a new population on Unib Island in the southwestern Dinagat extends the previously known distribution of this gekkonid by approximately 100 km south from its known distribution.
... Interestingly, we found very low or no representation of lepidopterans and dipterans that are generally attracted to artificial light. Dietary studies on geckos inhabiting urban areas have found high frequencies of lepidopterans and dipterans, thought to be due to artificial lighting (Powell et al. 1990;Saenz 1996;Tkaczenko et al. 2014;Barragán-Ramírez et al. 2015;Akintunde et al. 2020). Geckos found away from artificial lighting, however, have been found to have higher proportions of non-flying insects (Iturriaga and Marrero 2013). ...
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Human-induced alterations have had a profound impact on the environment affecting several species. Many lizards, however, especially members of the gecko genus Hemidactylus, are cosmopolitan and are found living on buildings in urban areas. Nevertheless, how some reptiles colonize and thrive in human-altered habitats remain relatively less explored, partly due to the lack of adequate natural history on different species. Here, we study the natural history of Prashad's Gecko (Hemidactylus prashadi), a poorly studied, large-bodied gecko, which is believed to have recently colonized houses in the study region. We report new populations of this species extending the range further south to Kerala, India. We also studied the demographic structure, spatial partitioning, diet, and reproduction of the lizard in a residential building in Kozhikode district, Kerala. We found the population in the building was dominated by adult females and juveniles, while adult males and sub-adults were few. Perch height and non-lethal injuries of individuals on the building suggest intense intraspecific competition and spatial partitioning between juveniles and adults. Diet was mostly arthropods but showed low frequency of light-attracted insects. Reproduction extended from November to May with a clutch size of two eggs, but we also observed an instance of possible communal nesting. Overall, our study provides detailed natural history of a population of H. prashadi, which has recently started occupying human-altered habitats.
... data) and therefore may encounter the food item before the native. Hemidactylus frenatus are efficient foragers of arthropods (Canyon & Hii 1997;Tkaczenko et al. 2014), often actively searching for prey, as opposed to many Australian native geckos, which are predominantly sit-and-wait ambush predators (Cogger 2014). In addition to arthropod prey, H. frenatus will prey upon juvenile lizards of native species (Fig. 1c) and cannibalise other invasive geckos (both H. frenatus and Mourning geckos, Lepidodactylus lugubris; Bolger & Case 1992;E.J. Nordberg, pers. ...
The introduction of the Asian house gecko, Hemidactylus frenatus, to mainland Australia has sparked considerable debate in regard to its potential impacts on native lizard species. Their historically patchy distribution across Australia has gained attention as populations have spread into peri‐urban and native bushland. Hemidactylus frenatus potentially pose a threat to native species through competition and predation. I documented some activity of H. frenatus during the day, including foraging, which may broaden the potential impacts to diurnal species. Here, I highlight (i) the potential impact of predation by H. frenatus on native lizards and (ii) the need for empirical studies directly quantifying competitive encounters, with special interest in intraguild predation.
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The risks of Aedes aegypti and Aedes albopictus nuisance and vector‐borne diseases are rising and the adverse effects of broad‐spectrum insecticide application has promoted species‐specific techniques, such as sterile insect technique (SIT) and other genetic strategies, as contenders in their control operations. When specific vector suppression is proposed, potential effects on predators and wider ecosystem are some of the first stakeholder questions. These are not the only Aedes vectors of human diseases, but are those for which SIT and genetic strategies are of most interest. They vary ecologically and in habitat origin, but both have behaviourally human‐adapted forms with expanding ranges. The aquatic life stages are where predation is strongest due to greater resource predictability and limited escape opportunity. These vectors' anthropic forms usually use ephemeral water bodies and man‐made containers as larval habitats; predators that occur in these are mobile, opportunistic and generalist. No literature indicates that any predator depends on larvae of either species. As adults, foraging theory predicts these mosquitoes are of low profitability to predators. Energy expended hunting and consuming will mostly outweigh their energetic benefit. Moreover, as adult biomass is mobile and largely disaggregated, any predator is likely to be a generalist and opportunist. This work, which summarises much of the literature currently available on the predators of Ae. aegypti and Ae. albopictus, indicates it is highly unlikely that any predator species depends on them. Species‐specific vector control to reduce nuisance and disease is thus likely to be of negligible or limited impact on non‐target predators.
We examined differences in the physiology and life history between dimorphs of the common pistachio psyllid, Agonoscena pistaciae (Burckhardt and Lauterer) (Hemiptera: Aphalaridae), and how they differ in elicitating host plant production of key metabolites and volatile compounds involved in the recruitment of herbivores and natural enemies. Summer morphs had higher activities of glutathione S-transferase, carboxylesterase, acetylcholinesterase, and cytochrome P450 monooxygenase, superoxide dismutase, catalase, peroxidase, phenoloxidase, and a higher total protein content compared to winter morphs, whereas the latter had higher amounts of lipid, carbohydrate, and glycogen. Winter morphs were heavier, with a higher chitin content and longer preoviposition period, but greater fecundity and longevity than summer morphs. A lower LC50 to thiamethoxam for winter morphs resulted in higher mortality following exposure to the recommended rate of this insecticide in a greenhouse trial. Feeding by winter morphs elicited more strongly the release of volatile compounds known to be attractive to other herbivores, whereas feeding by summer morphs elicited more strongly the release of volatiles implicated in the attraction of natural enemies. Feeding by psyllids increased the concentrations of nitrogenous compounds, carbohydrates, vitamins, and amino acids in plants, the winter morph eliciting larger changes and more improved host plant quality. We conclude that winter morphs are more vulnerable targets for chemical control in early spring, whereas management of summer morphs could rely more on conservation biological control.
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Invasive animals can have a wide range of impacts in natural systems. The introduced Asian house gecko Hemidactylus frenatus has invaded widely in Australia, but is largely restricted to human-altered landscapes. Hoskin (2011) has argued that H. frenatus has the potential to negatively impact Australian ecosystems by invading natural habitats. We examine this contention by reviewing an extensive standardised fauna survey dataset collected in northern and central Queensland during the key period of H. frenatus expansion from the 1990s to 2012. In light of these data we also re-examine data from other areas that suggest H. frenatus is a benign threat and is unlikely to become an environmental pest within Australia. On current evidence, we conclude that H. frenatus is unlikely to spread much beyond areas of human influence.
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The feeding habits of insectivorous bats are of great interest to people, because they are considered to be important in the control of insect pests. Here we present a study showing the relationship of bat morphology to differences in prey selection by various bat species. We compared dietary data from 10,884 faecal pellets, bodyweight, cranial length, forearm length and echolocation calls from published peer-reviewed studies for 92 bat species. We demonstrated that insectivorous bats tend to prefer certain insect orders which we have grouped as soft bodied insects, hard bodied insects and Lepidoptera. Wing characteristics which we measured by bodyweight-forearm ratio showed the strongest relationship with hard insects followed by longest cranial length. The content of soft insects in bat diets was negatively related to bodyweight, forearm length and longest cranial length. Lepidoptera content was positively related to the echolocation frequency with the maximum intensity (FMAXE), bats with high FMAXE fed on more Lepidoptera than those with low frequencies. We propose that a combination of dietary analysis and morphological analysis is needed to make strong inference about prey preference rather than comparing the dietary analysis with the insect abundance at the location were the bat or faecal pellets were collected.
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We investigated the predation rates of three common jumping spiders (Salticidae) on mosquitoes (Culicidae) in Southeast Asia. We released mosquitoes from the genus Armigeres in a terrarium together with single predatory spiders for a period of approximately 24 hours. Predation rates differed among spider species and among sexes: mean predation rates (± SE) for Plexippus petersi were 6.0 (±0.8) mosquitoes per day for male spiders and 9.2 (±0.85) for female spiders. Male spiders of the species Plexippus paykulli consumed 4.3 (±1.2) mosquitoes per day and female spiders fed on 10.8 (±1.6) mosquitoes per day. For Menemerus bivittatus the predation rates were 2.7 (±1.3) and 4.7 (±2.3) mosquitoes per day for male and female spiders respectively. For all species, female spiders fed on significantly more mosquitoes than male spiders. Mosquito density positively affected predation rates, but this effect was small. The observed predation rates are high relative to estimates for other mosquito predators, leading to the conclusion that salticids, particularly Plexippus spp, have the potential to be valuable biological control agents for mosquitoes.
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The aim of this work was to study the diet of Hemidactylus frenatus in an urban area of Colombian Caribbean region. Twenty five specimens were captured on human edifications at the Sincelejo municipality (Sucre). After dissection and analysis of the stomach content, we identify 12 prey groups being Hemiptera the item with the highest importance value index (IVI = 152.7). The data shows a generalist and opportunistic feeding pattern, feeding mainly on arthropods.
The pholcid spider. Crossopriza lyoni (Blackwall 1867) is a common inhabitant of homes in a rural village in Chachoengsao Province, Thailand. Studies on the spider were initiated because its microhabitat closely coincided with with of adult Aedes aegypti (Linnaeus 1762), mosquito vectors of dengue virus. Laboratory observations showed that females deposited eggs 4-6 days after copulation. Females held the egg sac in their mouthparts for 11-13 days, until all spiderlings (mean = 34) had left the sac. Spiderlings did not feed until they had molted, but as soon as feeding commenced they were capable of overpowering a mosquito many times their own size. Sometimes spiderlings would share a single mosquito or eat a mosquito wrapped by the mother spider. Spiderlings separated from their mother grew more rapidly than those left with the mother and reached maturity in as little as 74 days. The spiders' principal means of capturing prey was to throw silk with the aid of the hind legs. Spiders used this method to immobilize mosquitoes which were entangled in the standing web or to catch flying mosquitoes. The mosquito was not bitten until the time of feeding, up to six days after capture. Feeding occurred on only 34-48% of the days, and spiders ate about one mosquito per day. Cannibalism was a significant mortality factor, accounting for 67-84% mortality in a cage of spiderlings. An enzyme-linked immunosorbent assay (ELISA) was adapted to test spider tissue for presence of dengue virus. The ELISA was used to show that spiders did not become infected when fed dengue-infected mosquitoes. The results of the study suggested that C. lyoni could form an important component of integrated control of Aedes aegypti mosquitoes in foci of dengue transmission.
The population dynamics of termites can be described according to the life history strategies evolved by the species in the different phases of colony life, though few studies have involved the search for patterns in termite life history, linked with the evolution of colony fitness. Dispersal is important for the successful establishment of the new colony, as well as reproductive isolation between species. Possible dispersion by budding is recently recognized The colony founding stage appears a very critical step for the future success, especially the balance of energy income with energy losses and the constraints faced by the first brood of workers. During the different phases of the colony growth, trade-offs are operating within the nest population. With colony sizes and caste dynamics, it is difficult to identify general patterns, due to variable reliability of data. Different methods have been adopted, from direct total sampling of the nest population to indirect estimates, including the mark-release-recapture method. The strategies of resource use within and between colonies are one of the major factors regulating nest density. Functional group assemblages and the territoriality of termite nests could explain their spatial patterns. Intraspecific competition, together with predation are major constraints in the population dynamics of termites.
Science is about discovering new things, about better understanding processes and systems, and generally furthering our knowledge. Deep in science philosophy is the notion of hypotheses and mathematical models to represent these hypotheses. It is partially the quantification of hypotheses that provides the illusive concept of rigor in science. Science is partially an adversarial process; hypotheses battle for primacy aided by observations, data, and models. Science is one of the few human endeavors that is truly progressive. Progress in science is defined as approaching an increased understanding of truth – science evolves in a sense.
It is shown by example how a cumulative link mixed model is fitted with the clmm2 function in package ordinal. Model interpretation and inference is briefly discussed. A tutorial for the more recent clmm function is work in progress. We will consider the data on the bitterness of wine from Randall (1989) presented in Table 1 and available as the object wine in package ordinal. The data were also analyzed with mixed effects models by Tutz and Hennevogl (1996). The following gives an impression of the wine data object:> data(wine)> head(wine) response rating temp contact bottle judge 1 36 2 cold no 1 1 2 48 3 cold no 2 1 3 47 3 cold yes 3 1 4 67 4 cold yes 4 1 5 77 4 warm no 5 1 6 60 4 warm no 6 1> str(wine) ✬data.frame✬: 72 obs. of 6 variables:
The concept of ' hardness' has long been used to describe the biomechanical properties of the diet of many animals. However, due to the lack of a consistent definition, and the multitude of uses to which the term has been put, the use of the term ' intractability' has been advocated here to represent the extent to which the structural strength, stiffness and toughness are increased in a foodstuff. The thickness of the cuticle of an insect was a good measure of the intractability of cuticle. The tremendous advantage of the use of cuticle thickness as a measure of the biomechanical properties of invertebrates means that the dietary properties of a living insectivore can be directly quantified according to the thickness of the cuticle in its faeces. The quantitative measurement of intractability obtained through this technique can be used in correlations with adaptations of the masticatory apparatus, including tooth and skull morphology, as well as more general considerations of ecology. This is a major advance on previous measures of the biomechanical properties of insectivore diets, and may represent the best technique of any dietary group in assessing the properties of its diet.