Range extension and new ecoregion records of the Crocodile Monitor Varanus salvadorii (Peters & Doria, 1878) (Reptilia: Varanidae) in Papua New Guinea

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Borja Reh
Jim Thomas


The Crocodile Monitor Varanus salvadorii is one of the longest lizards and an apex predator in New Guinea. Limited information is available on its ecology and distribution, mainly due to its arboreal lifestyle and preference for inaccessible primary forest habitats. Here we provide the first published record, using camera trapping technology in the Torricelli Mountain Range, of V. salvadorii living at a higher elevation than previously recorded in montane rainforest habitat. This range extension implies the occupation of a distinctive ecoregion for the species: the Northern New Guinea Montane Forest, a substantially cooler region from the formerly known distribution area. We present trail camera images of an active animal at an elevation of 1,500 m & at 18oC temperature and we discuss the implications of this finding for understanding the behaviour & conservation of the Crocodile Monitor.

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Adams, C. (1995). Taxon management account: Crocodile or Papuan monitor Varanus salvadorii, pp. 85-90. In: Hartdegen, R. (eds.). Asian Forest Monitor North American Regional Studbook. 3rd edition. Dallas Zoo, USA, 144pp.

Allison, A. (1996). Zoogeography of amphibians and reptiles of New Guinea and the Pacific region. pp. 407-436 In: Keast, A. & S. E. Miller (eds.). The Origin and Evolution of Pacific Island Biotas, New Guinea to Eastern Polynesia: Patterns and Processes. SPB Academic Publishing, Amsterdam, The Netherlands, 531pp.

Allison, A. (2006). Reptiles and amphibians of the Trans-Fly region, New Guinea. Pacific Biological Survey, 50 pp.

Amindoni, A. & R. Henschke (2020). The burning scar: Inside the destruction of Asia’s last rainforests. BBC News. https://www.bbc.com/news/world-asia-54798452

Ariefiandy, A., D. Purwandana, A. Seno, C. Ciofi & T.S. Jessop (2013). Can Camera Traps Monitor Komodo Dragons a Large Ectothermic Predator? PLoS ONE 8(3): e58800. https://doi.org/10.1371/journal.pone.0058800

Beehler, B.M. & D.M. Prawiradilaga (2010). New taxa and new records of birds from the north coastal ranges of New Guinea. Bulletin of the British Ornithologists’ Club 130: 277–285.

Bryan, J. E., P. Shearman & University of Papua New Guinea (2015). The state of the forests of Papua New Guinea 2014: Measuring change over the period 2002–2014.

Curtis, P.G., C.M. Slay, N.L. Harris, A. Tyukavina & M.C. Hansen (2018). Classifying drivers of global forest loss. Science 361(6407): 1108–1111. https://doi.org/10.1126/science.aau3445

Bryan, J.E. & P. L. Shearman (2008). Papua New Guinea Resource Information System Handbook (3rd edition). University of Papua New Guinea. https://png-data.sprep.org/dataset/resource-mapping

Camina, Á., N. Salinas & J. Cuevas (2013). Husbandry and breeding of the crocodile monitor Varanus salvadorii Peters & Doria, 1878 in captivity. Biawak 7(2): 56–62.

Dalsgaard, S., & M. Pedersen (2015). The portable sawmill and other challenges to REDD+ in Papua New Guinea: REDD+ in Papua New Guinea. Asia Pacific Viewpoint 56(1): 128–139. https://doi.org/10.1111/apv.12086

Diamond, J. M. (1985). New Distributional Records and Taxa from the Outlying Mountain Ranges of New Guinea. Emu - Austral Ornithology 85(2): 65–91. https://doi.org/10.1071/MU9850065

Dinerstein, E., D. Olson, A. Joshi, C. Vynne, N. D. Burgess, E. Wikramanayake, N. Hahn, S. Palminteri, P. Hedao, R. Noss, M. Hansen, H. Locke, E. C. Ellis, B. Jones, C.V. Barber, R. Hayes, C. Kormos, V. Martin, E. Crist, W. Sechrest, L. Price, J.E.M. Baillie, D. Weeden, K. Suckling, C. Davis, N. Sizer, R. Moore, D. Thau, T. Birch, P. Potapov, S. Turubanova, A. Tyukavina, N. de Souza, L. Pintea, J.C. Brito, O.A. Llewellyn, A.G. Miller, A. Patzelt, S.A. Ghazanfar, J. Timberlake, H. Klöser, Y. Shennan-Farpón, R. Kindt, J-P. Barnekow Lillesø, P. van Breugel, L. Graudal, M. Voge, K.F. Al-Shammari & M. Saleem (2017). An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm. BioScience 67(6): 534–545. https://doi.org/10.1093/biosci/bix014

Flannery, T. F. (1995). Mammals of New Guinea (Rev. and updated ed). Comstock/Cornell.

Gregory, T., F. Carrasco-Rueda, J. Deichmann, J. Kolowski, & A. Alonso (2014). Arboreal camera trapping: Taking a proven method to new heights. Methods in Ecology and Evolution 5(5): 443–451. https://doi.org/10.1111/2041-210X.12177

Heads, M. (2002). Regional Patterns of Biodiversity in New Guinea Animals. Journal of Biogeography 29(2): 285–294.

Heinsohn, T. & G. Hope (2006). The Torresian connections: Zoogeography of New Guinea, pp. 71–93. In: Evolution and Biogeography of Australian Vertebrates. Australian Scientific Publishing.

Horn, H.G. (2004). Varanus salvadorii, pp. 234–244. In Pianka, E.R., D.R. King & R.A. King (eds.). Varanoid Lizards of the World. Indiana University Press, 608 pp. https://doi.org/10.2307/j.ctt2005wjp.11

Horn, H.G., S.S. Sweet & K.M. Philipp (2007). On the distribution of the Papuan Monitor (Varanus salvadorii Peters & Doria, 1878) in New Guinea. Advances in Monitor Research 3(16): 25–43.

Schwartz, K.R., O. Byers, P. Miller, J. Blessington & B. Smith (2021). The Role of Zoos in Tree Kangaroo Conservation: Connecting Ex Situ and In Situ Conservation Action. En Tree Kangaroos. Elsevier, pp. 329-361 pp. https://doi.org/10.1016/B978-0-12-814675-0.00026-9

Shea, G., A. Allison, F. Parker, M. O’Shea & O. Tallowin (2016). Varanus salvadorii: The IUCN Red List of Threatened Species 2016: e.T42485775A42485784 [Data set]. International Union for Conservation of Nature. https://doi.org/10.2305/IUCN.UK.2016-1.RLTS.T42485775A42485784.en

Jessop, T. S., M. R. Kearney, J. L. Moore, T. Lockwood & M. Johnston (2013). Evaluating and predicting risk to a large reptile (Varanus varius) from feral cat baiting protocols. Biological Invasions 15(8): 1653–1663. https://doi.org/10.1007/s10530-012-0398-3

Kraus, F. (2010). More range extensions for Papuan reptiles and amphibians. Herpetological Review 41: 246–248.

Kraus, F., & A. Allison (2006). Range extensions for reptiles and amphibians along the northern versant of Papua New Guinea. Herpetological Review 37: 364–368.

Letsoin, S.M.A., D. Herak, F. Rahmawan & R.C. Purwestri (2020). Land Cover Changes from 1990 to 2019 in Papua, Indonesia: Results of the Remote Sensing Imagery. Sustainability 12(16): 6623.

Mays, S. (2007). Husbandry and captive propagation of the crocodile monitor, Varanus salvadorii, at the Houston Zoo. Advances in Monitor Research III. Mertensiella 16: 422–429.

Miettinen, J., C. Shi & S. C. Liew (2011). Deforestation rates in insular Southeast Asia between 2000 and 2010. Global Change Biology, 17(7): 2261–2270.

Mittermeier, R. A., C. G. Mittermeier, T. M. Brooks, J. D. Pilgrim, W. R. Konstant, G. A. Da Fonseca & C. Kormos (2003). Wilderness and biodiversity conservation. Proceedings of the National Academy of Sciences 100(18): 10309–10313.

Mittermeier, R. A., W. R. Turner, F. W. Larsen, T. M. Brooks & C. Gascon (2011). Global Biodiversity Conservation: The Critical Role of Hotspots, pp. 3–22. In Zachos, F.E. & J.C. Habel (eds.). Biodiversity Hotspots: Distribution and Protection of Conservation Priority Areas. Springer, https://doi.org/10.1007/978-3-642-20992-5_1

Moore, J. F., K. Soanes, D. Balbuena, C. Beirne, M. Bowler, F. Carrasco‐Rueda, S. M. Cheyne, O. Coutant, P. Forget, J. K. Haysom, P. R. Houlihan, E. R. Olson, S. Lindshield, J. Martin, M. Tobler, A. Whitworth & T. Gregory (2021). The potential and practice of arboreal camera trapping. Methods in Ecology and Evolution 12(10): 1768–1779. https://doi.org/10.1111/2041-210X.13666

Pattiselanno, F. (2007). Varanus Species at The Arfak Strict Nature Reserve. Biodiversitas, Journal of Biological Diversity 8: 114–117. https://doi.org/10.13057/biodiv/d080208

Philipp, K.M. and D.P. Philipp (2007). The monitor lizards of Papua, pp. 617–636. In: Marshall, A.J. & B.M. Beehler (eds.). The Ecology of Papua-Part One. Periplus Editions (HK), Singapore, 784 pp.

PNG Data Portal (2021). Forest Cover in PNG | Papua New Guinea Environment Data Portal. https://png-data.sprep.org/resource/forest-cover-png

Ray, J.C. (2005). Large carnivorous animals as tools for conserving biodiversity: assumptions and uncertainties, pp. 34–56. In: Ray, J.C., K.H. Redford, R.S. Steneck & J. Berger (eds.). Large Carnivores and the Conservation of Biodiversity. Island Press, Washington, D.C.

Reh, B., J. Recuero, Y. Heng, C. R. Shepherd, A. Reeves, R. Haines, T. Trout, S. Mays, M. Wenninger & S. S. Sweet (2021). EAZA Best Practice Guidelines for the Crocodile Monitor (Varanus salvadorii). European Association of Zoos and Aquariums, Amsterdam, The Netherlands.

Richards, S.J. (2007). A Rapid Biodiversity Assessment of the Kaijende Highlands, Enga Province, Papua New Guinea. Conservation International Chicago Distribution Center http://www.bioone.org/doi/book/10.1896/978-1-934151-08-2

Sergio, F., T. Caro, D. Brown, B. Clucas, J. Hunter, J. Ketchum, K. McHugh & F. Hiraldo (2008). Top predators as conservation tools: Ecological rationale, assumptions, and efficacy. Annual Review of Ecology, Evolution, and Systematics 39: 1–19.

Simberloff, D. (1998). Flagships, umbrellas, and keystones: Is single-species management passé in the landscape era? Biological Conservation 83(3): 247–257.

Thomas, J. (2014). Fauna survey by camera trapping in the Torricelli Mountain Range, Papua New Guinea. Camera Trapping: Wildlife Management and Research. CSIRO Publishing, Melbourne, Australia, 69–76.

Trout, T. (2007). Observation of breeding and nesting behaviors in captive Varanus salvadorii. Mertensiella 16: 441–447.

Vizzuality (2010). Papua New Guinea Deforestation Rates & Statistics | GFW. https://www.globalforestwatch.org/dashboards/country/PNG

Waterloo, B. & M. K. Bayless (2006). Notes on the breeding behaviour of the crocodile monitor (Varanus salvadorii) in captivity. Herpetological Bulletin (98): 2–6.

Wikramanayake, E. D., E. Dinerstein, & C. J. Loucks (2002). Terrestrial ecoregions of the Indo-Pacific: A conservation assessment 3. Island Press, Washington D.C., 553–555 pp.

Yamazaki, D., D. Ikeshima, R. Tawatari, T. Yamaguchi, F. O’Loughlin, J. Neal C., C. C. Sampson, S. Kanae & P. D. Bates (2017). A high-accuracy map of global terrain elevations. Geophysical Research Letters 44(11): 5844–5853. https://doi.org/10.1002/2017GL072874