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Tim S Jessop - One of the best experts on this subject based on the ideXlab platform.
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Knee deep in trouble: rusa deer use an aquatic escape behaviour to delay attack by Komodo dragons
Australian Mammalogy, 2020Co-Authors: Achmad Ariefiandy, Deni Purwandana, Yunias Jackson Benu, Mike Letnic, Tim S JessopAbstract:We document six observations of an aquatic behaviour used by rusa deer (Rusa timorensis) to delay an imminent attack from Komodo dragons (Varanus komodoensis). This unusual behaviour arose after rusa deer fled into the nearby seawater following an attack from a solitary Komodo dragon. Once in the sea, rusa deer remained relatively stationary by standing in shallow water (
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Exploring mechanisms and origins of reduced dispersal in island Komodo dragons.
Proceedings. Biological sciences, 2018Co-Authors: Tim S Jessop, Jeri Imansyah, Deni Purwandana, Achmad Ariefiandy, Claudio Ciofi, David M. Forsyth, Yunias Jackson Benu, Damien A. Fordham, Raoul A. Mulder, Benjamin L. PhillipsAbstract:Loss of dispersal typifies island biotas, but the selective processes driving this phenomenon remain contentious. This is because selection via, both indirect (e.g. relaxed selection or island syndromes) and direct (e.g. natural selection or spatial sorting) processes may be involved, and no study has yet convincingly distinguished between these alternatives. Here, we combined observational and experimental analyses of an island lizard, the Komodo dragon (Varanus komodoensis, the world's largest lizard), to provide evidence for the actions of multiple processes that could contribute to island dispersal loss. In the Komodo dragon, concordant results from telemetry, simulations, experimental translocations, mark-recapture, and gene flow studies indicated that despite impressive physical and sensory capabilities for long-distance movement, Komodo dragons exhibited near complete dispersal restriction: individuals rarely moved beyond the valleys they were born/captured in. Importantly, lizard site-fidelity was insensitive to common agents of dispersal evolution (i.e. indices of risk for inbreeding, kin and intraspecific competition, and low habitat quality) that consequently reduced survival of resident individuals. We suggest that direct selection restricts movement capacity (e.g. via benefits of spatial philopatry and increased costs of dispersal) alongside use of dispersal-compensating traits (e.g. intraspecific niche partitioning) to constrain dispersal in island species.
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Assessment of environmental and host dependent factors correlated with tick abundance on Komodo dragons
The Australian zoologist, 2016Co-Authors: Tim S Jessop, Joanna Sumner, Jeri Imansyah, Deni Purwandana, Aganto Seno, Achmad Ariefiandy, Claudio CiofiAbstract:In this study we assessed interactions among Komodo dragon Varanus komodoensis populations, individual Komodo dragons and two tick parasites Amblyomma robinsoni and Aponomma komodoense to assess variation in host-parasite aggregations. Prevalence of ticks was uniformly high (> 98%) but median tick abundance varied 3.52 fold among 9 host lizard populations. There was no evidence to suggest that average tick abundances were correlated with genetic similarities (Rm = 0.133, P = 0.446) or geographic proximities (Rm = 0.175 P=0.303) among host populations. Temporal concordance in tick abundance was measured for host populations between two different years but not for the individual hosts within these populations. General linearized modelling indicated that ≈ 23% of host variation in tick abundance was positively correlated to a multivariate function incorporating lizard body size, body condition, their interactions, and habitat differences. The covariates of host population density and inbreeding coefficients,...
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Visual comparison of cranial and mandibular morphology between specimens.
2015Co-Authors: Matthew R. Mccurry, Tim S Jessop, Stephen Wroe, Phillip D Clausen, Michael Mahony, Michelle R. Quayle, Christopher W. Walmsley, Heather Richards, Colin R. MchenryAbstract:The morphology of each specimen is shown in dorsal and lateral view for both the cranium and mandible. Species are ordered by cranial PC1 values. Abbreviations: H.hor, Heloderma horridum; L.bor, Lanthanotus borneensis; V.aca, Varanus acanthurus; V.exa, Varanus exanthematicus; V.gou, Varanus gouldii; V.kom, Varanus komodoensis; V.pan h, Varanus panoptes horni; V.pan p, Varanus panoptes panoptes; V.pra, Varanus prasinus; V.sdi, Varanus salvadorii; V.slt, Varanus salvator; V.stor, Varanus storri; V.tri, Varanus tristis.
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First record of komodo dragon nesting activity and hatchling emergence from North Flores, Eastern Indonesia
2015Co-Authors: Achmad Ariefiandy, Deni Purwandana, Claudio Ciofi, Sanggar Abdil Nasu, Maman Surahman, Tim S JessopAbstract:For wild varanid populations, basic measures of reproductive ecology, such as distribution and selection of nest sites, are difficult to obtain. To date, nest distributions and nesting behavior for Komodo dragons (Varanus komodoensis) have only been reported from Komodo National Park. Here we report the first record of V. komodoensis nesting activity and hatchling emergence on Ontoloe Island, off the north coast of Flores. This is a significant finding for it suggests that this relatively small but well protected island supports a viable population of V. komodoensis
Claudio Ciofi - One of the best experts on this subject based on the ideXlab platform.
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Isolating Chromosomes of the Komodo Dragon: New Tools for Comparative Mapping and Sequence Assembly.
Cytogenetic and genome research, 2019Co-Authors: Alessio Iannucci, Claudio Ciofi, Marie Altmanová, Michail Rovatsos, Petr Velenský, Ivan Rehák, Malcolm A. Ferguson-smith, Jorge C. Pereira, Roscoe Stanyon, Lukáš KratochvílAbstract:We developed new tools to build a high-quality chromosomal map of the Komodo dragon (Varanus komodoensis) available for cross-species phylogenomic analyses. First, we isolated chromosomes by flow sorting and determined the chromosome content of each flow karyotype peak by FISH. We then isolated additional Komodo dragon chromosomes by microdissection and amplified chromosome-specific DNA pools. The chromosome-specific DNA pools can be sequenced, assembled, and mapped by next-generation sequencing technology. The chromosome-specific paint probes can be used to investigate karyotype evolution through cross-species chromosome painting. Overall, the set of chromosome-specific DNA pools of V. komodoensis provides new tools for detailed phylogenomic analyses of Varanidae and squamates in general.
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Exploring mechanisms and origins of reduced dispersal in island Komodo dragons.
Proceedings. Biological sciences, 2018Co-Authors: Tim S Jessop, Jeri Imansyah, Deni Purwandana, Achmad Ariefiandy, Claudio Ciofi, David M. Forsyth, Yunias Jackson Benu, Damien A. Fordham, Raoul A. Mulder, Benjamin L. PhillipsAbstract:Loss of dispersal typifies island biotas, but the selective processes driving this phenomenon remain contentious. This is because selection via, both indirect (e.g. relaxed selection or island syndromes) and direct (e.g. natural selection or spatial sorting) processes may be involved, and no study has yet convincingly distinguished between these alternatives. Here, we combined observational and experimental analyses of an island lizard, the Komodo dragon (Varanus komodoensis, the world's largest lizard), to provide evidence for the actions of multiple processes that could contribute to island dispersal loss. In the Komodo dragon, concordant results from telemetry, simulations, experimental translocations, mark-recapture, and gene flow studies indicated that despite impressive physical and sensory capabilities for long-distance movement, Komodo dragons exhibited near complete dispersal restriction: individuals rarely moved beyond the valleys they were born/captured in. Importantly, lizard site-fidelity was insensitive to common agents of dispersal evolution (i.e. indices of risk for inbreeding, kin and intraspecific competition, and low habitat quality) that consequently reduced survival of resident individuals. We suggest that direct selection restricts movement capacity (e.g. via benefits of spatial philopatry and increased costs of dispersal) alongside use of dispersal-compensating traits (e.g. intraspecific niche partitioning) to constrain dispersal in island species.
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Assessment of environmental and host dependent factors correlated with tick abundance on Komodo dragons
The Australian zoologist, 2016Co-Authors: Tim S Jessop, Joanna Sumner, Jeri Imansyah, Deni Purwandana, Aganto Seno, Achmad Ariefiandy, Claudio CiofiAbstract:In this study we assessed interactions among Komodo dragon Varanus komodoensis populations, individual Komodo dragons and two tick parasites Amblyomma robinsoni and Aponomma komodoense to assess variation in host-parasite aggregations. Prevalence of ticks was uniformly high (> 98%) but median tick abundance varied 3.52 fold among 9 host lizard populations. There was no evidence to suggest that average tick abundances were correlated with genetic similarities (Rm = 0.133, P = 0.446) or geographic proximities (Rm = 0.175 P=0.303) among host populations. Temporal concordance in tick abundance was measured for host populations between two different years but not for the individual hosts within these populations. General linearized modelling indicated that ≈ 23% of host variation in tick abundance was positively correlated to a multivariate function incorporating lizard body size, body condition, their interactions, and habitat differences. The covariates of host population density and inbreeding coefficients,...
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First record of komodo dragon nesting activity and hatchling emergence from North Flores, Eastern Indonesia
2015Co-Authors: Achmad Ariefiandy, Deni Purwandana, Claudio Ciofi, Sanggar Abdil Nasu, Maman Surahman, Tim S JessopAbstract:For wild varanid populations, basic measures of reproductive ecology, such as distribution and selection of nest sites, are difficult to obtain. To date, nest distributions and nesting behavior for Komodo dragons (Varanus komodoensis) have only been reported from Komodo National Park. Here we report the first record of V. komodoensis nesting activity and hatchling emergence on Ontoloe Island, off the north coast of Flores. This is a significant finding for it suggests that this relatively small but well protected island supports a viable population of V. komodoensis
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Conservation of Komodo dragons Varanus komodoensis in the Wae Wuul nature reserve, Flores, Indonesia: a multidisciplinary approach
International Zoo Yearbook, 2014Co-Authors: Achmad Ariefiandy, Deni Purwandana, Tim S Jessop, Chiara Natali, M. J. Imansyah, M. Surahman, Claudio CiofiAbstract:Multidisciplinary conservation initiatives are increasingly advocated as best practice for recovering endangered species. The Komodo dragon Varanus komodoensis is the world's largest lizard, of prominent conservation value as an umbrella species for protection of south-east Indonesian ecosystems. Komodo dragons have faced multiple human-related threat processes in the past 30 years and are listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and considered Vulnerable according to the International Union for Conservation of Nature Red List. We report on a protection programme conducted from 2005 to 2012 in the Wae Wuul nature reserve, on the island of Flores, Indonesia. The Wae Wuul ranger post was completely rebuilt, and community awareness and involvement of local people in habitat-protection schemes were regularly and successfully implemented. Local rangers were trained in wildlife-monitoring techniques. Monitoring results indicated that Komodo dragon densities were lower in Wae Wuul than in the adjacent Komodo National Park; however, a relatively high level of genetic diversity was recorded for this population. Ungulate prey showed a relatively stable prey population density. Community-based initiatives and regular wildlife monitoring are crucial to ensure the persistence of Komodo dragons on Flores. The Wae Wuul protection programme is providing several sustainability indicators by which informed management plans can be designed for long-term conservation of Komodo dragons.
Robert J Blumenschine - One of the best experts on this subject based on the ideXlab platform.
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Using striated tooth marks on bone to predict body size in theropod dinosaurs: a model based on feeding observations of Varanus komodoensis, the Komodo monitor
Paleobiology, 2012Co-Authors: Domenic C. D'amore, Robert J BlumenschineAbstract:Mesozoic tooth marks on bone surfaces directly link consumers to fossil assemblage formation. Striated tooth marks are believed to form by theropod denticle contact, and attempts have been made to identify theropod consumers by comparing these striations with denticle widths of contemporaneous taxa. The purpose of this study is to test whether ziphodont theropod consumer characteristics can be accurately identified from striated tooth marks on fossil surfaces. We had three major objectives (1) to experimentally produce striated tooth marks and explain how they form; (2) to determine whether body size characteristics are reflected in denticle widths; and (3) to determine whether denticle characters are accurately transcribed onto bone surfaces in the form of striated tooth marks. We conducted controlled feeding trials with the dental analogue Varanus komodoensis (the Komodo monitor). Goat (Capra hircus) carcasses were introduced to captive, isolated individuals. Striated tooth marks were then identified, and striation width, number, and degree of convergence were recorded for each. Denticle widths and tooth/body size characters were taken from photographs and published accounts of both theropod and V. komodoensis skeletal material, and regressions were compared among and between the two groups. Striated marks tend to be regularly striated with a variable degree of branching, and may co-occur with scores. Striation morphology directly reflects contact between the mesial carina and bone surfaces during the rostral reorientation when defleshing. Denticle width is influenced primarily by tooth size, and correlates well with body size, displaying negative allometry in both groups regardless of taxon or position. When compared, striation widths fall within or below the range of denticle widths extrapolated for similar-sized V. komodoensis individuals. Striation width is directly influenced by the orientation of the carina during feeding, and may underestimate but cannot overestimate denticle width. Although body size can theoretically be estimated solely by a striated tooth mark under ideal circumstances, many caveats should be considered. These include the influence of negative allometry across taxa and throughout ontogeny, the existence of theropods with extreme denticle widths, and the potential for striations to underestimate denticle widths. This method may be useful under specific circumstances, especially for establishing a lower limit body size for potential consumers.
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komodo monitor Varanus komodoensis feeding behavior and dental function reflected through tooth marks on bone surfaces and the application to ziphodont paleobiology
Paleobiology, 2009Co-Authors: Domenic C Damore, Robert J BlumenschineAbstract:Abstract Most functional interpretations of ziphodont dentition are based on limited morphometric, behavioral, and taphonomic studies, but few are based on controlled observations of a modern ziphodont consumer. The purpose of this study is to determine through controlled feeding observations if the behaviors indicative of a ziphodont consumer are reflected by tooth marks left on bone surfaces by Varanus komodoensis, the Komodo monitor. We document feeding behavior, expand upon dental function, and correlate these aspects with tooth mark production. We also discuss the significance and limits of applying these data to fossil assemblages. Goat carcasses were fed to 11 captive individuals. V. komodoensis modifies bone surfaces extensively. Individuals exhibit a “medial-caudal arc” when defleshing, followed by inertial swallowing. Bone crushing was not observed. The vast majority of tooth marks are scores, with pits being significantly less common. Tooth furrows and punctures are rare. “Edge marks” are produ...
Lukáš Kratochvíl - One of the best experts on this subject based on the ideXlab platform.
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Shared Ancient Sex Chromosomes in Varanids, Beaded Lizards, and Alligator Lizards
Molecular Biology and Evolution, 2019Co-Authors: Michail Rovatsos, Petr Velenský, Ivan Rehák, Lukáš KratochvílAbstract:: Sex determination in varanids, Gila monsters, beaded lizards, and other anguimorphan lizards is still poorly understood. Sex chromosomes were reported only in a few species based solely on cytogenetics, which precluded assessment of their homology. We uncovered Z-chromosome-specific genes in varanids from their transcriptomes. Comparison of differences in gene copy numbers between sexes across anguimorphan lizards and outgroups revealed that homologous differentiated ZZ/ZW sex chromosomes are present in Gila monsters, beaded lizards, alligator lizards, and a wide phylogenetic spectrum of varanids. However, these sex chromosomes are not homologous to those known in other amniotes. We conclude that differentiated sex chromosomes were already present in the common ancestor of Anguimorpha living in the early Cretaceous or even in the Jurassic Period, 115-180 Ma, placing anguimorphan sex chromosomes among the oldest known in vertebrates. The analysis of transcriptomes of Komodo dragon (Varanus komodoensis) showed that the expression levels of genes linked to anguimorphan sex chromosomes are not balanced between sexes. Besides expanding our knowledge on vertebrate sex chromosome evolution, our study has important practical relevance for breeding and ecological studies. We introduce the first, widely applicable technique of molecular sexing in varanids, Gila monsters, and beaded lizards, where reliable determination of sex based on external morphology is dubious even in adults.
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Isolating Chromosomes of the Komodo Dragon: New Tools for Comparative Mapping and Sequence Assembly.
Cytogenetic and genome research, 2019Co-Authors: Alessio Iannucci, Claudio Ciofi, Marie Altmanová, Michail Rovatsos, Petr Velenský, Ivan Rehák, Malcolm A. Ferguson-smith, Jorge C. Pereira, Roscoe Stanyon, Lukáš KratochvílAbstract:We developed new tools to build a high-quality chromosomal map of the Komodo dragon (Varanus komodoensis) available for cross-species phylogenomic analyses. First, we isolated chromosomes by flow sorting and determined the chromosome content of each flow karyotype peak by FISH. We then isolated additional Komodo dragon chromosomes by microdissection and amplified chromosome-specific DNA pools. The chromosome-specific DNA pools can be sequenced, assembled, and mapped by next-generation sequencing technology. The chromosome-specific paint probes can be used to investigate karyotype evolution through cross-species chromosome painting. Overall, the set of chromosome-specific DNA pools of V. komodoensis provides new tools for detailed phylogenomic analyses of Varanidae and squamates in general.
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First Description of the Karyotype and Sex Chromosomes in the Komodo Dragon (Varanus komodoensis)
Cytogenetic and genome research, 2016Co-Authors: Martina Johnson Pokorná, Marie Altmanová, Michail Rovatsos, Petr Velenský, Roman Vodicka, Ivan Rehák, Lukáš KratochvílAbstract:The Komodo dragon (Varanus komodoensis) is the largest lizard in the world. Surprisingly, it has not yet been cytogenetically examined. Here, we present the very first description of its karyotype and sex chromosomes. The karyotype consists of 2n = 40 chromosomes, 16 macrochromosomes and 24 microchromosomes. Although the chromosome number is constant for all species of monitor lizards (family Varanidae) with the currently reported karyotype, variability in the morphology of the macrochromosomes has been previously documented within the group. We uncovered highly differentiated ZZ/ZW sex microchromosomes with a heterochromatic W chromosome in the Komodo dragon. Sex chromosomes have so far only been described in a few species of varanids including V. varius, the sister species to Komodo dragon, whose W chromosome is notably larger than that of the Komodo dragon. Accumulations of several microsatellite sequences in the W chromosome have recently been detected in 3 species of monitor lizards; however, these accumulations are absent from the W chromosome of the Komodo dragon. In conclusion, although varanids are rather conservative in karyotypes, their W chromosomes exhibit substantial variability at the sequence level, adding further evidence that degenerated sex chromosomes may represent the most dynamic genome part.
Deni Purwandana - One of the best experts on this subject based on the ideXlab platform.
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Knee deep in trouble: rusa deer use an aquatic escape behaviour to delay attack by Komodo dragons
Australian Mammalogy, 2020Co-Authors: Achmad Ariefiandy, Deni Purwandana, Yunias Jackson Benu, Mike Letnic, Tim S JessopAbstract:We document six observations of an aquatic behaviour used by rusa deer (Rusa timorensis) to delay an imminent attack from Komodo dragons (Varanus komodoensis). This unusual behaviour arose after rusa deer fled into the nearby seawater following an attack from a solitary Komodo dragon. Once in the sea, rusa deer remained relatively stationary by standing in shallow water (
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Exploring mechanisms and origins of reduced dispersal in island Komodo dragons.
Proceedings. Biological sciences, 2018Co-Authors: Tim S Jessop, Jeri Imansyah, Deni Purwandana, Achmad Ariefiandy, Claudio Ciofi, David M. Forsyth, Yunias Jackson Benu, Damien A. Fordham, Raoul A. Mulder, Benjamin L. PhillipsAbstract:Loss of dispersal typifies island biotas, but the selective processes driving this phenomenon remain contentious. This is because selection via, both indirect (e.g. relaxed selection or island syndromes) and direct (e.g. natural selection or spatial sorting) processes may be involved, and no study has yet convincingly distinguished between these alternatives. Here, we combined observational and experimental analyses of an island lizard, the Komodo dragon (Varanus komodoensis, the world's largest lizard), to provide evidence for the actions of multiple processes that could contribute to island dispersal loss. In the Komodo dragon, concordant results from telemetry, simulations, experimental translocations, mark-recapture, and gene flow studies indicated that despite impressive physical and sensory capabilities for long-distance movement, Komodo dragons exhibited near complete dispersal restriction: individuals rarely moved beyond the valleys they were born/captured in. Importantly, lizard site-fidelity was insensitive to common agents of dispersal evolution (i.e. indices of risk for inbreeding, kin and intraspecific competition, and low habitat quality) that consequently reduced survival of resident individuals. We suggest that direct selection restricts movement capacity (e.g. via benefits of spatial philopatry and increased costs of dispersal) alongside use of dispersal-compensating traits (e.g. intraspecific niche partitioning) to constrain dispersal in island species.
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Assessment of environmental and host dependent factors correlated with tick abundance on Komodo dragons
The Australian zoologist, 2016Co-Authors: Tim S Jessop, Joanna Sumner, Jeri Imansyah, Deni Purwandana, Aganto Seno, Achmad Ariefiandy, Claudio CiofiAbstract:In this study we assessed interactions among Komodo dragon Varanus komodoensis populations, individual Komodo dragons and two tick parasites Amblyomma robinsoni and Aponomma komodoense to assess variation in host-parasite aggregations. Prevalence of ticks was uniformly high (> 98%) but median tick abundance varied 3.52 fold among 9 host lizard populations. There was no evidence to suggest that average tick abundances were correlated with genetic similarities (Rm = 0.133, P = 0.446) or geographic proximities (Rm = 0.175 P=0.303) among host populations. Temporal concordance in tick abundance was measured for host populations between two different years but not for the individual hosts within these populations. General linearized modelling indicated that ≈ 23% of host variation in tick abundance was positively correlated to a multivariate function incorporating lizard body size, body condition, their interactions, and habitat differences. The covariates of host population density and inbreeding coefficients,...
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First record of komodo dragon nesting activity and hatchling emergence from North Flores, Eastern Indonesia
2015Co-Authors: Achmad Ariefiandy, Deni Purwandana, Claudio Ciofi, Sanggar Abdil Nasu, Maman Surahman, Tim S JessopAbstract:For wild varanid populations, basic measures of reproductive ecology, such as distribution and selection of nest sites, are difficult to obtain. To date, nest distributions and nesting behavior for Komodo dragons (Varanus komodoensis) have only been reported from Komodo National Park. Here we report the first record of V. komodoensis nesting activity and hatchling emergence on Ontoloe Island, off the north coast of Flores. This is a significant finding for it suggests that this relatively small but well protected island supports a viable population of V. komodoensis
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Conservation of Komodo dragons Varanus komodoensis in the Wae Wuul nature reserve, Flores, Indonesia: a multidisciplinary approach
International Zoo Yearbook, 2014Co-Authors: Achmad Ariefiandy, Deni Purwandana, Tim S Jessop, Chiara Natali, M. J. Imansyah, M. Surahman, Claudio CiofiAbstract:Multidisciplinary conservation initiatives are increasingly advocated as best practice for recovering endangered species. The Komodo dragon Varanus komodoensis is the world's largest lizard, of prominent conservation value as an umbrella species for protection of south-east Indonesian ecosystems. Komodo dragons have faced multiple human-related threat processes in the past 30 years and are listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and considered Vulnerable according to the International Union for Conservation of Nature Red List. We report on a protection programme conducted from 2005 to 2012 in the Wae Wuul nature reserve, on the island of Flores, Indonesia. The Wae Wuul ranger post was completely rebuilt, and community awareness and involvement of local people in habitat-protection schemes were regularly and successfully implemented. Local rangers were trained in wildlife-monitoring techniques. Monitoring results indicated that Komodo dragon densities were lower in Wae Wuul than in the adjacent Komodo National Park; however, a relatively high level of genetic diversity was recorded for this population. Ungulate prey showed a relatively stable prey population density. Community-based initiatives and regular wildlife monitoring are crucial to ensure the persistence of Komodo dragons on Flores. The Wae Wuul protection programme is providing several sustainability indicators by which informed management plans can be designed for long-term conservation of Komodo dragons.
