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Skyfall#- an extreme case of male-male aggression in Tokay Geckos (Gekkonidae- Gekko gecko) on Ataúro Island, Timor-Leste

Tokay geckos (Fig. 1) are a noisy fixture in Southeast
Asian rainforests, issuing their onomatopoetic calls
from dusk to dawn (and sometimes even during the
day) from diverse perches throughout a wide range of
microhabitats, ranging from pristine to disturbed areas
(e.g., Manthey and Grossmann, 1997; Chan et al., 2006;
Grismer, 2011). Unfortunately, these geckos (especially
their tongues!) have become threatened in their native
habitats by international trade, and their conservation
is becoming an international priority (Bauer, 2009;
Subramanean and Reddy, 2012). Given how well this
species advertises itself in its habitats and how high of
an interest it commands in the field of herpetoculture
(e.g., McKeown and Zaworski, 1997; Toth, 2020)
and traditional medicine, it may be surprising that
very few studies, as opposed to faunal surveys, deal
directly with the ecology and behaviour of the species.
Outside of the many notes on G. gecko, in which single
dietary observations and aspects of natural history in
introduced populations are reported, we found exactly
two studies detailing the natural history of G. gecko
more broadly and in what is presumed to be its native
habitat, namely Stanner et al. (1998) and Aowphol et
al. (2006). Furthermore, even though there is ample
mention in the literature, as well as in online reports, of
the aggressive behaviour shown by the species towards
humans and other geckos (e.g., Grismer, 2011; Kaiser
et al., 2013) this behaviour appears to be a matter of
general knowledge, yet there are no formal studies or
scientific reports documenting this##. Our report fills
a gap in our understanding to show the extent of this
species’ aggressiveness.
Ataúro Island is a small (area 105 km2) Inner Banda
Arc island of volcanic origin and lies ca. 25 km off
the coast of Dili, the capital city of Timor-Leste. It
has a fairly diverse reptile fauna, of which G. gecko
is an audible, integral part (see Kaiser et al., 2013).
On 31 January 2010, during our first survey to assess
the island’s herpetofauna, we witnessed an unusual
behavioural episode involving G. gecko. While eight
of us were walking along the island’s main road in the
evening (19:30 h) from Tua Ko’in Lodge (8.2531°S,
125.6072°E) southwards to the town of Vila, we heard
G. gecko calls along the road. At one point, in a grove
of tall trees that formed a canopy over the road, we
heard a brief (< 1 min duration) noisy squabble above
us, which culminated when a tokay gecko landed on the
road right at our feet. This male individual displayed
Herpetology Notes, volume 13: 969-971 (2020) (published online on 26 November 2020)
: an extreme case of male-male aggression in
Tokay Geckos (Gekkonidae: Gekko gecko) on Ataúro
Island, Timor-Leste
Hinrich Kaiser1,* and Mark O’Shea2
1 Department of Biology, Victor Valley College, 18422
Bear Valley Road, Victorville, California 92395, USA;
and Department of Vertebrate Zoology, Zoologisches
Forschungsmuseum Alexander Koenig, Adenauerallee 160,
53113 Bonn, Germany.
2 Faculty of Science and Engineering, University of
Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY,
United Kingdom.
* Corresponding author. E-mail:
# Our title is a reference to the highly acclaimed 2012 James
Bond film with the same name. Bond films are filled with
male-male aggression, and in this case the topic of our paper
literally fell from the sky. The title of the film actually ref-
erences Skyfall, Commander Bond’s childhood home in the
Scottish Highlands.
## Of course, as a popular terrarium animal, there exist reports
about male-male aggression of G. gecko in captivity. For ex-
ample, Borg and Borg (1981) observed how three wild-caught
tokays from Bali fought and injured each other after having
been placed into a terrarium, which led Borg (2004) to issue
a “main rule” for keeping this species: do not keep males to-
Hinrich Kaiser & Mark O’Shea
no righting response or other movement and appeared
dead. Shining our flashlights immediately up into the
trees (approximate height 6 m above the road) allowed
us to see an especially large G. gecko retreating along
the length of a large overhanging branch. Closer
investigation of the deceased individual (deposited in
the collection of the United States National Museum,
Smithsonian Institution, accession number USNM
579056) revealed a definite set of bloody toothmarks
on both sides of its body and across its ribcage (more
visible on the lighter-coloured venter), a match to the
dimensions and dentition of G. gecko.
We reconstruct the episode as follows. Two adult male
geckos with territories in trees on either side of the road
forage along the edges of their respective territories and
encounter each other on a branch over the road, which
acts as a connector between established territories.
In the ensuing agonistic encounter, both individuals
vocalise and proceed to square off, including attempts to
bite. During this vicious engagement, one gecko gains
a firm hold on the other via a strong bite, inadvertently
killing it in the process. Facing no further resistance and
sensing no movement, the victor ends his struggle and
releases the loser, who unceremoniously drops down to
the road.
Our reconstruction of this tokay gecko aggression
event, which was heard but only partially observed,
is not merely based on assumptions but on solid
circumstantial evidence. During our walk that evening,
as on all night walks during survey periods, we looked
into the surrounding vegetation with flashlights. Based
on the absence of rats, snakes, or birds in general
during our walk and specifically along the branch and
trees where the observation took place (and absent any
rustling caused by other animals in the vicinity) and our
knowledge of the different vocalisations produced by G.
gecko (Yu et al., 2011), we discount the interpretation
that our auditory observation was related to something
other than intraspecific aggression. We had heard the
characteristic territorial calls of the species numerous
times from the bushes and trees lining the road and
beyond. The overheard squabble involved clear
intimidation „barks“ (sensu Brillet and Payette, 1991),
to the exclusion of other types of vocalisation (i.e., this is
inconsistent with a failed mating or predation attempt).
The bite force of G. gecko (Montuelle and Williams,
2015; Ross et al., 2018) is strong enough to break
through the carapaces of large insects and the bones
of small vertebrates, and it may well be forceful
enough to squeeze the ribcage of a conspecific to exert
sufficiently strong and sudden pressure on the heart and
internal organs to cause death. We do not believe that
the fall from the branch and the impact with the road
had any causation in the demise of the individual we
examined, given that tokays may jump some distance
and there was absolutely no post-fall movement. While
vocalisations are commonly used by these geckos in
territorial displays and agonistic encounters, the type of
intraspecific aggression we report here has never been
documented in detail. Doubtlessly, many people have
seen agonistic encounters, on account of G. gecko being
firmly established in disturbed areas and even cities
(Grismer, 2011), but only Chan et al. (2006) mentioned
any intraspecific aggression among males. One probable
reason for this is that most agonistic conflicts between
G. gecko males do not lead to the fairly spectacular
death of one of the combatants. We do not wish to imply
that fighting to the death is anything other than a very
rare and unintended consequence of regular territorial
conflicts between conspecifics that are ordinarily
relatively well-matched, but this encounter serves to
illustrate the extreme vigor with which male G. gecko
defend their territories from their rivals.
Acknowledgments. We thank our incredible fieldwork team,
including Venancio Lopes Carvalho, Laca Agivedo Varela, Zito
Afranio Soares, Luis Lemos de Araujo, Jester Ceballos, Scott
Heacox, Eric Leatham, Caitlin Sanchez, Dan Suzio, Marianna
Tucci, and “MJ” Weil for their eyes, ears, and nimble feet and
fingers to allow us an assessment of the Ataúro herpetofauna.
We very much appreciate the help of Aaron Bauer, who once
Figure 1. Aggressive pose of a male Gekko gecko from Ataúro
Island, Timor-Leste. While this is not one of the individuals
involved in the altercation we describe herein, the photo serves
to illustrate the fierce disposition and sharp dentition of these
sizable lizards. Photo by Mark O’Shea.
again came through with a key reference. We also gratefully
acknowledge the support and interest of Manuel Mendes, Director
of National Parks, who issued our research and export permits.
Our visits to Ataúro were supported by stipends to HK from a
Title V Grant to Victor Valley College and by financial assistance
to our U.S.-based students from the Associate Student Body at
Victor Valley College and the Victor Valley College Foundation.
This paper is Contribution No. 23 from the Tropical Research
Initiative at Victor Valley College.
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An extreme case of male-male aggression in Tokay Geckos, Timor-Leste 971
Accepted by Maximilian Dehling
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
Cranial kinesis refers to movements of skeletal sub-units relative to one another at mobile sutures within the skull. The presence and functional significance of cranial kinesis has been investigated in various vertebrates, with much of our understanding coming from comparative studies and manipulation of ligamentous specimens. Drawing on these studies, cranial kinesis in lizards has been modeled as a four-bar linkage system involving streptostyly (rotation of the quadrate), hypokinesis (dorsoventral flexion and extension of the palato-maxillary sub-unit), mesokinesis (dorsoventral flexion and extension of the snout at the fronto-parietal suture) and metakinesis (sliding movements between parietal and supraocciptal bones). In vivo studies, although limited, suggest that cranial kinesis serves an important role during routine behaviors such as feeding. Here, we use X-ray Reconstruction Of Moving Morphology to further quantify mesokinesis in vivo in Gekko gecko during three routine behaviors: gape display, biting and post-ingestion feeding. During gape display, the snout rotates dorsally above rest position, with mesokinesis accounting for a 10% increase in maximum gape over that achieved solely by the depression of the lower jaw. During defensive biting, the snout rotates ventrally below rest position to participate in gape closure. Finally, ventroflexion of the snout also occurs during post-ingestion feeding, accounting for 42% of gape closure during intra-oral transport, 86% during puncture-crushing, and 61% during pharyngeal packing. Mesokinesis thus appears to facilitate prey puncturing by allowing the snout to rotate ventrally so that the upper teeth pierce the prey item, thus limiting the need for large movements of the lower jaw. This is suggested to maintain a firm grip on the prey and reduce the possibility of prey escape. More generally, this study demonstrates that mesokinesis is a key component of defensive biting and gape display behaviors, as well as post-ingestion feeding, all of which are linked to organismal fitness.
Full-text available
Geographic variations in vocalizations and morphological characteristics of the tokay gecko (Gekko gecko L.) complex were identified using subjects recorded and/or collected in China and Southeast Asia. Populations in south China and northeast Vietnam (the black tokay) were compared with those in Thailand, Laos and south Vietnam (the red tokay). Red tokays possess gray- or dark green-colored skin with brick red spots interspersed on the dorsum, while black tokays possess dark-green skin with black spots or spots of other colors except brick red. Each group produces advertisement calls which consist of distinct acoustic phases. In both groups the first call phase consists of a series of pulses and the second phase consists of a series of two-note syllables. Only red tokays produce a third phase consisting of single notes. Frequency modulation patterns were profoundly different for call elements produced between the two groups. Calls of the black but not red tokay exhibit intricate frequency modulated elements with silent periods between pulses in the first phase and between syllables in the second phase. In the red tokay little or no frequency modulation was observed and no silent intervals were found between pulses or syllables. For both groups the acoustics of the pulses produced in the first phase varied among animals, suggesting it may function for individual identification while the second phase appears to identify the group (red vs black tokay). Thus the tokay complex has become differentiated geographically not only in terms of morphological characteristics but also in terms of call acoustics.
The tokay, Gekko gecko, is familiar as a pet and in the laboratory but is poorly studied in nature. We observed tokays in a village 50km N of Bangkok and during two nights recorded the foraging behavior of one individual. Although its activity varied between nights, the tokay clearly behaved as a ''sit and wait'' predator. Currently the tokay's worst enemy seems to be man, who hunts it for food and medicine, so that within Bangkok and in China the species is becoming rare.
In vivo bone strain data provide direct evidence of strain patterns in the cranium during biting. Compared with those in mammals, in vivo bone strains in lizard skulls are poorly documented. This paper presents strain data from the skulls of Anolis equestris, Gekko gecko, Iguana iguana and Salvator merianae during transducer biting. Analysis of variance was used to investigate effects of bite force, bite point, diet, cranial morphology and cranial kinesis on strain magnitude. Within individuals, the most consistent determinants of variance in bone strain magnitude were gauge location and bite point, with the importance of bite force varying between individuals. Intersite variance in strain magnitude – strain gradient – was present in all individuals and varied with bite point. Between individuals within species, variance in strain magnitude was driven primarily by variation in bite force, not gauge location or bite point, suggesting that inter-individual variation in patterns of strain magnitude is minimal. Between species, variation in strain magnitude was significantly impacted by bite force and species membership, as well as by interactions between gauge location, species and bite point. Independent of bite force, species differences in cranial strain magnitude may reflect selection for different cranial morphology in relation to feeding function, but what these performance criteria are is not clear. The relatively low strain magnitudes in Iguana and Uromastyx compared with those in other lizards may be related to their herbivorous diet. Cranial kinesis and the presence or absence of postorbital and supratemporal bars are not important determinants of inter-specific variation in strain magnitude.
Four types of vocalizations of the nocturnal lizard Gekko gecko (the ‘Tokay’) are described. A bark of intimidation, distress calls, a short not very intense call, apparently related to sexual inter-action, and a long, complex sequence. This ‘long sequence’ is considered to be a territorial proclamation which also functions as a mating-call. It has been analysed in detail with special emphasis on the intra-individual variations. The mean duration of this sequence is 22.3 s, the intensity is 70 dB at 1m and the maximum of energy is between 300 and 4000 Hz. This sequence is composed of three phases. The first one consists of several multipulse sounds called ‘rattles’, the second of bi-motifs which sound like a two syllable tok-kay, and the third, not always present, is a kind of ‘grumble’. The number of motifs and the occurrence of the third phase may vary but the duration of the motifs is relatively stable.
At least 14 species of geckos are utilized as ingredients in the pharmacopia of traditional medicine systems around the world. Chinese Traditional Medicine uses two types of geckos, large tokay geckos (Gekko gecko) and small geckos (Gekko spp., Hemidactylus spp.) to treat a diversity of ailments including asthma, tuberculosis, diabetes and cancer, and current research in China focuses on the identification of active ingredients in geckos and the verification of their efficacy. The actual number of species involved in the Chinese Traditional Medicine trade may be higher than currently realized due to the fraudulent sale of counterfeit geckos and accidental misidentification. The potential pool of species includes at least 37 species from throughout the broad area in which geckos and other wildlife are collected for use in China. Although powders and tablets pose difficulties for identification, the whole dried form in which geckos are often sold permits the identification of most species. A key is provided to the 12 species of geckos most likely to be encountered in the trade of Asian traditional medicine.
The foraging behavior of Gekko gecko was observed at the visitor complex of the Khao Khiao Open Zoo at the Khao Khiao-Khao Chomphu Wildlife Sanctuary in Chon Buri Province, Thailand. Foraging parameters of G. gecko (foraging period, time spent moving, foraging attempts, foraging success, prey size consumed, and foraging distance) did not vary significantly between males, females, and juveniles. Individuals foraged between 18:01 and 09:00 hrs. Peak emergence time was between 18:01 and 20:00 hrs. Peak retreat time was between 04:01 and 07:00 hrs. Major food items included insects of the orders Lepidoptera, Orthoptera, and Coleoptera. Prey sizes of males, females, and juveniles were not significantly different, indicating no prey size selection. This may have been due to low insect availability in the habitat. Gekko gecko tended to be a sit-and-wait forager spending most of the time waiting for active prey. However, it sometimes foraged more actively when insect abundance was relatively high. Foraging behavior of males tended to be more variable than females and juveniles. In addition, variation in foraging parameters among individuals was noted. Foraging strategies of G. gecko observed in this study are interpreted in the context of optimal foraging theory.
De tokkeh Gekko gecko: een eenvoudige handleiding
  • J Borg
  • Ter
Borg, J. ter (2004): De tokkeh Gekko gecko: een eenvoudige handleiding [a simple manual]. Lacerta 62(6): 256-260. [in Dutch]