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Incidence of Fish Hook Ingestion by Komodo dragons June 30, 2008

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Incidence of Fish Hook Ingestion by Komodo dragons

Tim Jessop1, Jeri Imansyah2, Deni Purwandana2, Achmad Arifiandy2 and Devi S. Opat3

1Department of Wildlife Conservation and Research, Zoos Victoria, PO Box 74 Parkville VIC 3052, Australia

2 Komodo Dragon Species Survival Program Indonesia, Denpasar, Bali, Indonesia.

3 Taman National Komodo, Labuan Bajo, Flores, NTT, Indonesia.

Correspondence to Tim Jessop

(e-mail: tjessop@ zoo.org.au).

The Komodo dragon (Varanus Komodoensis), a large robust monitor lizard, persists on the 5 islands in Eastern Indonesia (Ciofi and deBoer 2004). The waters surrounding these islands are intensively utilized for marine resources and in particular line and net fishing are prolific. For other reptiles, particularly freshwater and marine turtles, incidental injury and mortality through ingestion of fishing hooks during routine foraging activities are not uncommon (Polovina et al. 2000). However, similar incidents of reptile by-catch in terrestrial species is poorly documented even though, many large lizards such as monitors, are semi-aquatic or cohabit and forage within coastal areas in which intense fishing activities persist. Here we report two incidents of ingestion of fishing gear by Komodo dragon during routine monitoring of island populations between 2002- 2006.

Annual mark recapture studies were conducted at 10 sites across 4 islands within Komodo National Park during both 2002 and 2005 and resulted in 827 dragons captures(> post-hatchling size). From this sample, 2 cases of fishhook ingestion were reported. The first case, comprised a small monitor (Animal ID: 00063A9978, 69.35 cm SVL, 7 kg) captured at Loh Buaya (8:39:21.7 S, 119:43:06.2 N) on Rinca Island and appeared to occurred recently as the line protruding from its mouth was still relatively long and the nylon in good condition. Based on the line weight it is suspected that the hook ingested by this lizard was relatively small. This lizard was recaptured in 2005, without any evidence of the protruding fishing line (however if the hook was remaining is unknown) and it had grown 8.75 cm in SVL and increased its mass by 1.45 kg. The second lizard, an adult male (Animal ID: 000643A7EC, 127.75 cm SVL, 41.8 kg) was captured on the 19th June 2004 also from Rinca Island at Loh Tongker (8:45:31.1 S, 119:42:57.3 E) a small coastal valley on the south east coast. In this incident the hook ingested was likely to have been considerably larger and typical of those used for capturing large pelagic species on long line. This hook was shackled with 2 strands of heavy trace wire (Fig 1). In this instance it is believed the hook was ingested several weeks to months earlier as indicated by the lesion induced by abrasion from the trace wire. In 2005, this adult male was recaptured, there was no evidence of the protruding trace, however it was not known if the hook still resided within the animal. The weight of this male had decreased by 8.8 kg from 2004 and 20 kg from its first capture in 2003 despite growing relatively little in length (4 cm in SVL).

Consumptions of fishing hooks by Komodo dragons, albeit rare, is a likely consequence of these lizard’s prodigious scavenging capacity coinciding with discarded fishing gear that finds it way into the intertidal areas exposed on the low tide. As yet we do not know what effects hook ingestion might incur for the specific individuals dragons, however, given that mortality occurs readily in other reptiles, it is possible that at least in the case of the second animal there may be negative consequences.


Ciofi, C. & de Boer, M.E. 2004. Distribution and conservation of the Komodo Monitor (Varanus komodoensis). Herpetological Journal 14: 99-107.

Polovina, J.J., Kobayashi, D.R., Ellis, D.M., Seki, M.P., & Balazs, G.H., 2000. Turtles on the edge: Movement of loggerhead turtles (Caretta caretta) along oceanic fronts in the central North Pacific, 1997-1998. Fisheries Oceanography 9(1):71-82.

Ticks on emerged hatchlings of Komodo Dragon June 27, 2008

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Ticks on emerged hatchlings of Komodo Dragon (Varanus komodoensis) on Komodo island, Indonesia


Komodo Survival Program, Jl Pulau Moyo, Komplek Karantia Blok 2 no 4, Denpasar, Bali 80222, Indonesia



Zoos Victoria, PO Box 74, Parkville, Melbourne, VIC 3052, Australia


The ticks (Acarina) that parasitise varanid lizards (Sauridae) are mainly from two Genera; Amblyomma and Aponomma (King & Green, 1999). Ticks as ectoparasites consume host blood, cause disease and can function as important vectors for microparasites, which can negatively influence the fitness of reptiles (Main and Bull 2000). The Komodo dragon (Varanus komodoensis), a large monitor lizard, from South Eastern Indonesia has been documented to possess three species of tick including Amblyomma helvolum a generalist, and two host specific species- A. robinsoni and Aponomma komodoense (Auffenberg, 1981). In Zoos, Komodo also reported loaded by A. komodoense that were infested from wild specimens (Burridge et al., 2004). However as yet little is known about the ecology, or the fitness implications, of this host-parasite dynamic. One aspect of this host-parasite dynamic that remains unknown is the possibility that ticks have evolved strategies to parasitise hatchling dragons on emergence from their nests. From a parasites perspective, host environments of juvenile animals, are those that provide the east resistance with respect to immunological (i.e. lack of acquired immunity) or physical (eg skin thickness) barriers could provide greater benefit (reference). Herein we report on the capacity of ticks to parasitise recently emerged hatchling Komodo dragons from three nests on Komodo Island.

In January of each year (2003-2006) a sample of known active nests of V. Komodoensis were caged to enable capture of hatchlings as part of routine annual monitoring of the ecology and life-history of this species in Komodo National Park (Jessop et al., 2004). Prior to emergence in March/April (late wet season), nest cages were monitored twice daily (morning and afternoon coinciding with emergence of hatchlings from the ground) to enable measurement and marking of individual hatchlings prior to release. In 2004, we also examined for the presence of ectoparasites of hatchlings on Komodo Island, one of four extant populations within Komodo National Park.

From the three nests monitored on Komodo Island in 2004 (referred to as LSB1, LL64 and LSB3), 47 hatchling Komodo were captured in March (estimated within 4 hours post-emergence). Together these hatchlings has a mean- weight of 95.53 ± 2.20 gr and SVL 18.78 ± 0.14 cm. Hatchlings from two of the three nests, were found to be carrying nymphal ticks of one species, Aponomma komodoense. Two of the 18 hatchlings (11.11%) from nest LSB1 had ticks, one had 1 tick, the other had 3 (Table 1). Clutch LL64 had 16 individuals, of which 9 (8.333%) carried ticks. The number of ticks ranged from 1 to 20, with an average number of ticks per hatchling of 7.44 ± 2.46. Hatchlings (n =12) from nest LSB2 were not observed to carry ticks.

Table 1. Tick infestation of emerged hatchlings from two of three nests of Komodo dragon Varanus komodoensis on Komodo island.





Number of Ticks

Frequency with ticks











11 %








83 %








0 %

Our results indicate that alongside larger Komodo dragons, hatchlings can act as hosts for ticks. By parasitizing hatchlings on emergence, ticks could greatly increase their capacity to find new and potentially more importantly immunologically naïve hosts (i.e. no acquired resistance). Female dragons, which act as hosts for ticks, spend considerable periods of time around the nest both prior to and after oviposition and thus could enable ticks to deposit eggs (that remain quiescent) around the nest site until hatchlings emerge. Seasonal cues, including the conspicuous transition from an extended dry season through to the short summer wet season coinciding with the monsoon represent an important cue for many organisms breeding in the wet-dry tropics of Eastern Indonesia (Kerr and Bull, 2006; Monk et al., 1997). This seasonal cue could provide necessary environmental information enabling nymphal ticks to synchronise their own hatching and questing activity with the emergence of hatchling Komodo dragons (reference). At present we do not know of the specific fitness consequences that ticks impart on their hatchling hosts. While ticks can illicit fitness costs by reducing growth, condition and the locomotor capacity in other lizards, similar consequences for hatchling Komodo dragons remain to be determined (Hanson et al., 2007; Main and Bull, 2000).


We thank Ibrahim Payung, Heru Rudiharto, and Zamzam for their assistance during field work. Financial support was provided by a Millennium Post Doctoral Fellowship from the Zoological Society of San Diego (ZSSD) to TSJ. Approval for the research was granted under a MOU between ZSSD and The Nature Conservancy (Indonesia Program) and by the Indonesian Department of Forest Protection and Nature Conservation (PHKA).


Auffenberg, W. 1981. The Behavioral ecology of the Komodo dragon. Gainesville, University Florida Press.

Burridge, M.J., Leight-Anne Simmons, T.Condie. 2004. Control of an exotic tick Aponoma komodoense) infestatation in a Komodo dragon (Varanus komodoensis) exhibit at a zoo in Florida. Journal of Wildlife Medicine. 35(2): 248-249.

Hanson, B.A., P.A.Frank, J.W.Mertins, J.L.Corn. 2007. Tick paralysis of a snake caused by Amblyoma rotundatum (Acari: Ixodidae). Journal of Medical Entomology. 44(1): 155-157.

Jessop, T.J., Sumner, J., Rudiharto, H. Purwandana, D., Imansyah, M.J. & Philips, J.A. 2004. Study on nest distribution, utilization, and selection by Komodo dragon, Varanus komodoensis: implication for conservation and management. Biological Conservation. 117: 463-470.

Kerr, G. D., C.M. Bull,. 2006. Interaction between climate, host refuge use, and tick population dynamics. Parasitology Research. 99: 214-222.

King, D.R. & Green, B. 1999. Goannas: the biology of Varanid lizards. Sydney, New South Wales Press Ltd.

Main, A.R., Bull, C.M. 2000. The impact of tick parasites on the behaviour of the lizard Tiliqua rugosa. Oecologia 122: 574-581.


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Ruteng, 19 May 2008

M Jeri Imansyah, Deni Purwandana


To increase capacity of staff of KSDA NTT and to give introduction on Mark Recapture methodology and population analysis based on mark recapture data that prepared for Komodo dragon population estimation on Flores, a short training on Introduction of Mark recapture methodology and use of Ecological Methodology (Krebs, 2002) computer program to estimate animal population was carried out in the KSDA NTT Office in Ruteng.


Training was carried out during two sessions. The first session included lectures on basic of population study in animal, mark recapture, and application of “Ecological Methodology (Krebs, 2002)” computer program given by the instructor, followed by a discussion where trainees were asking questions and additional information on specific procedures. During the second session, an open discussion went through research methodology applied to animal population size estimates.


The training course was attended by 22 members of staff from Bidang II KSDA NTT. Open discussion mostly dealt with implementation of mark-recapture methods for estimating animal population size on Flores. Species of interest was the Komodo monitor Varanus komodoensis. However, since none of KSDA staff had been involved in previous field work involving mark-recapture, nor they were acquainted with data analysis, the training mostly focused on basic concepts and logistics for the implementation of methods in the field.

Conclusions and Recommendations

  1. The training material was perhaps too advance for KSDA NTT staff, since no one of them has been involved in mark-recapture studies before.
  2. Time available to explain the theory of mark-recapture methods was insufficient and further training sessions should be scheduled along with practical sessions involving KSDA staff in mark-recapture field techniques, for instance in Komodo National Park. Training sessions involving both KSDA NTT and KNP staff are therefore recommended.
  3. Further training sessions to consider the basics of mark-recapture methodology for the Komodo monitor in more details should be carried out, along with training on alternative census methodologies for population size estimates of other wildlife in Komodo National Park and Flores.


We thank Luhut Sihombing, the Head of Balai Besar KSDA NTT, and Suprihatna, head of Bidang II KSDA NTT, for organizing the training sessions. The course was part of an MoU between Komodo Survival Program and Balai Besar KSDA NTT. Funds were provided by the European Aquaria and Zoos Association.