Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 July 2022 | 14(7): 21402–21408
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.7808.14.7.21402-21408
#7808 | Received 29 December 2021 | Final
received 06 June 2022 | Finally accepted 26 June 2022
Range extension and new ecoregion
records of the Crocodile Monitor Varanus salvadorii (Peters & Doria,
1878) (Reptilia: Varanidae)
in Papua New Guinea
Borja Reh
1 & Jim Thomas 2
1 Allies for Wildlife, 266 Principe
de Vergara, 28016, Madrid, Spain.
2 Tenkile Conservation Alliance (TCA),
P.O. Box 365 Ravenshoe 4888 Queensland, Australia.
1 borjareh@a4w.org (corresponding
author), 2 help@tenkile.com
Abstract: 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.
Keywords: Distribution, monitor lizard,
Northern New Guinea Montane Forest, Tenkile
Conservation Alliance, threats, Torricelli Mountain Range.
Tok Pisin
Abstract: Bikpela stori bilong
dispela wok: Dispela pukpuk nem bilong
em Monitor Varanus
salvardorii em wanpla bigpla na longpela palai
tru na i
stap namba wan long Niu Gini olsem animol we i save killim na kaikai
olgeta arapela animol. Bikos dispela
pukpuk i save laik long stap antap tu long ol
diwai na laikim tumas bigpela
bush we nogat man i save
go, yumi nau no save tumas long ples we dispela pukpuk i save stap long em na tu
yumi no klia gud yet long wonem hap kona blo kantri
tru dispela pukpuk igo kamap
pinis.Mipla painim aut sampla moa nupla samtin long dispela pukpuk na nau mipla
wokim namba wan toksave long kantri na olgeta man meri
long ples graun olsem dispela pukpuk
V. salvadorii i stap tu long maunten
ples antap moa we ol lain bipo ino
bin lukim long em bikos ol i
bin painim em tasol long bus blo liklik maunten lo nambis sait tasol.
Mipela usim kamera olsem trap bilong kisim foto
long dispela pukpuk antap long maunten blo Torrecelli Range. Dispela luksave nau i soim
olsem pukpuk V.salvadorii i go stap antap long ol maunten na nupla hap tu: Em
long hailens bus na maunten bilong Sepik we ples i kol
na bipo dispela
pukpuk ino bin stap long em.Ol dispela piksa mipla
i soim em
bilong dispela pukpuk i raun
painim kaikai we kemera i kisim
long em antap long maunten i sanap
olsem 1,500 m na ples i kol
olsem long 18oC. Mipla i stori tu
long wonem samtin i mas kamap nau
antap long dispela save na wonem wei
tru yumi ken wok wantaim long lukautim dispela pukpuk Monitor V. salvadorii.
Editor: S.R. Ganesh,
Chennai Snake Park, Chennai, India. Date
of publication: 26 July 2022 (online & print)
Citation: Reh,
B. & J. Thomas (2022). Range extension and new ecoregion
records of the Crocodile Monitor Varanus salvadorii (Peters & Doria,
1878) (Reptilia: Varanidae)
in Papua New Guinea. Journal of Threatened Taxa 14(7): 21402–21408. https://doi.org/10.11609/jott.7808.14.7.21402-21408
Copyright: © Reh
& Thomas 2022. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: None.
Competing interests: The authors
declare no competing interests.
Author details: Borja Reh is a herpetologist and project manager focused on wildlife
conservation. He is the co-founder of Allies for Wildlife and currently works
as Accreditation Coordinator at the European Association of Zoos and
Aquaria. Jim Thomas is a
zoologist and a conservationist who is devoted to saving species in the
Torricelli Mountain Range. He has been the Project Manager and Chief Executive
Officer of the Tenkile Conservation Alliance since
2003.
Author contributions: Both authors have participated in
organizing and analyzing the data. BR wrote the manuscript and JT wrote the
methods and revised the manuscript.
Acknowledgements: We want to thank Steve Platt and
Tim Jessop for their invaluable assistance in the preparation of this manuscript,
Alberto García-Rodríguez for assisting with the GIS maps, and Redley Opasa for translating the
abstract to Tok Pisin.
We are grateful to the villages of the Torricelli Mountain Range—Wai’eli, Wuguble, Maiwetem, Wolwalem, Souleite, Waunulu, Yongite, Rawate, Wilbeite, Miwaute, Wabute, Sarborte, Tolgete, Wigote 1, Wigote 2, Yomoum, Lilal, Mupun, Bagam,
Uwei, Wiekint, Nunsi, Awang, Winbe, Muku, Sumil, Yapunda,
Marakumba, Paita, Sibilanga, Asier, Barkop, Aluna, Swara, Yanungen, Mup, Selep, Brau,
Kolembi, and King villages. Lastly, thanks to Cecilia Encinas
and Claudia Reh-Encinas for their support.
INTRODUCTION
New Guinea is considered a
high-biodiversity wilderness area, an important region for conservation that
combines a large percentage of intact habitats with rich endemism,
exceptionally diverse biota, and low human population density (Richards 2007;
Mittermeier et al. 2011). With the
remaining natural forest cover extending over 90% of its land, Papua New Guinea
(hereafter PNG) is one of the least explored regions in the world (Mittermeier
et al. 2003; Vizzuality 2010; PNG Data Portal 2021).
The Torricelli Mountain Range is among the remotest areas of this island
(Diamond 1985; Flannery 1995; Kraus & Allison 2006; Beehler
& Prawiradilaga 2010; Thomas 2014). Located
primarily in Sandaun Province (northwestern PNG), the
Torricelli Mountains form the northern coastal range of PNG together with
Prince Alexandre and Bewani Mountains stretching from
the East Sepik Province to the Keerom regency in
Papua province (Indonesia) in the west (Image 1). These mountains are part of
the New Guinea north coastal ranges which also includes the Cyclops, Foja, and Van Rees mountains located in Papua province. The
Torricelli Mountains consist of limestone and montane forest and harbours
several endemic vertebrate and invertebrate species, and the description of new
species is considered very likely (Flannery 1995; Allison 1996; Wikramanayake et al. 2002; Kraus 2010; Thomas 2014).
Furthermore, this area is considered the third most diverse region for lizards
in New Guinea (Heads 2002). The Torricelli Mountain Range is enveloped by two
key biodiversity areas (KBAs), the East and West Torricelli’s, and is a
proposed conservation area (Dalsgaard & Pedersen 2015; Schwartz et al.
2021).
The Crocodile Monitor Varanus salvadorii
is the largest lizard of New Guinea and an apex predator on this island (Heinsohn & Hope 2006). A handful of studies exist on
this elusive species in captivity (Adams 1995; Waterloo & Bayless 2006;
Mays 2007; Trout 2007; Camina et al. 2013; Reh et al. 2021) but V. salvadorii
has been poorly studied in the wild, mainly because it is restricted to
commonly inaccessible forests, strictly avoids contact with humans, and
predominantly displays arboreal behaviour (Horn et al. 2007; Pattiselanno 2007; Shea et al.
2016).
The distribution of the species
includes lowland and hill forests around most of the coastal lowlands of New
Guinea. However, it has not been reported to occur in habitats above 600 m. The
species has previously been reported from open woodland habitats within the
Trans-Fly region, and lowland and mangrove forests on the islands of Salawati, Warir, and Selat Sagawin (north-west tip of
Papua) (Allison 2006; Horn et al. 2007; Borja Reh
pers. comm. 1.xii.2009). Crocodile Monitors are excellent swimmers, and
individuals have been observed in forests along rivers (Marshall & Beehler 2011).
Here we report the first
discovery of Crocodile Monitors in the Torricelli Mountain Range captured with
trail camera traps at elevations above 1,000 m.
MATERIALS
AND METHODS
The Tenkile
Conservation Alliance (TCA) has been conducting research in the Torricelli
Mountain Range since 2002. From 2002 a total of 16 sites have been established
for sampling, specifically point transect sampling and initially for scat
surveys for tree kangaroos. Each research site consists of 20 transects with a
total of 150 transect points for scat surveys and setting camera traps. Camera
trapping began in 2010 with six camera traps. From 2013 to 2018, the number of
cameras increased to 30, and in 2019 the number reached to 50 camera traps.
TCA uses Reconyx
cameras (models 650 and 850) that are rotated for each survey, and no more than
25 are deployed at any one time. The cameras are attached to a tree 30 cm above
the ground, the area is cleared of debris and tested before being set for each
survey. Camera traps are left in the field for three months before being
collected, and then results are analysed. Further information regarding camera
trap setup by the TCA can be found at the link https://tenkile.com/wp-content/uploads/2022/02/Camera-Trap-Field-Manual.pdf
Each camera trap survey consists
of a team of 12 people from the villages close to the research site. Each team
consists of four research officers and eight rangers.
The trail cameras provide
temperature data, time of capture, and moon phase. When triggered by motion
sensors, predefined settings of the trail cameras are to take three photos at
three-second intervals and leave a 10-minute delay to prevent repeated
photography of the same individual.
The elevation is recorded at each
trail camera location with a Garmin GPS and confirmed using the map of global
terrain elevations by Yamazaki et al. (2017).
The images collected are reviewed
by experts looking at key indicators of species such as colour pattern, size,
posture, and the shape of the body. The animals are also compared with
sympatric species of the same family.
RESULTS
Over the
study period, TCA could collect data from 140 GPS camera monitoring sites
ranging at elevations 700–1,600 m, corresponding to the Northern New Guinea
Montane Forest ecoregion (Wikramanayake et al. 2002)
(Image 2). More than 10,000 images have been collected from the camera traps.
Birds and mammals account for the majority of animal photos. Only two reptile
species (V. salvadorii and V. doreanus) were recorded by camera traps.
Two
Crocodile Monitors were photographed, with camera traps in the Torricelli
Mountain Range. The first was at the ‘Waliapilk’
research site in 2012, and at the second at the ‘Birr’ research site in 2015.
Both sites are outside the previously known elevation distribution range for
the species (Image 3).
Individual
1, a suspected adult of unknown gender was captured at 1032 h on 12 August
2012, at ground level and 1,522 m elevation with an air temperature of 18 °C.
GPS location 3.4075 °S & 142.1819 °E. Although a series of three images
were taken, only the first image shows enough of the animal to identify the
species (Image 4).
Individual
2, a suspected adult of unknown gender was captured at 1114 h on 8 August 2015,
at ground level and 1,200 m elevation when the air temperature was 20°C. GPS
location 3.4038 °S & 142.2205 °E. The animal was walking at a normal pace
(Image 5).
DISCUSSION
Elevation
distribution data of V. salvadorii were
compiled by Horn et al. (2007) based on available data. The authors reported 25
locations from museum specimens and 20 specimens from the literature and direct
observations. Most individuals were recorded below 200 m, with two exceptions
at 550 and 600 m. Pattiselanno et al. (2007) reported
one Crocodile Monitor in the Arfak Mountains at 650
m. The locations we describe herein confirm an elevational range extension of
Crocodile Monitors based on reliable photo records of the species in the
Torricelli Mountain Range. Moreover, it indicates the tolerance of Crocodile
Monitors to a new ecoregion, the Northern New Guinea Montane Forest.
Although
principally deployed to capture images of tree kangaroos, camera traps set by
TCA in the Torricelli Mountain Range have successfully recorded species of all
terrestrial vertebrates (Thomas 2014). The Tenkile
and Weimang tree kangaroos are the flagship species
for TCA; however, unexpected results, such as those for V. salvadorii, are welcomed and emphasise the importance
of protected areas and biodiversity monitoring.
The present
findings also shed some light on the possibility of V. salvadorii
occurring in the North Coastal Ranges of PNG (Bewani-Torricelli-Prince
Alexander Mountain Ranges) after several reports of ‘kundu
drums’ made with Crocodile Monitor skin in villages in that region (Horn et al.
2007). The species has been ever-present in the area, being revered, feared and
respected. Traditional stories by the Tambuna tribe
people suggest the animal can attain great lengths and consume village hunting
dogs. Small animals have been caught, and their skins are used for making drums
(Jim Thomas pers. comm. 10.xii.2021). However, due to their life history traits
they are difficult to observe without camera traps.
TCA has used
camera traps in the Torricelli Mountain Range since 2010, but only two
Crocodile Monitors have so far been recorded. This could be due to an extremely
low population density in the region or due to the setting of the cameras at
low height not targeting this species specifically, or because no bait lures
were used. Crocodile Monitors are mainly arboreal, spending most of their time
in trees (Reh et al. 2021).
This species
is known to inhabit a range of habitats, including rainforest vegetation such as
mixed alluvial and mixed hill forest types, as well as lowland and riparian
forests (Horn 2004; Horn et al. 2007). Additionally, the present data indicate
that the Crocodile Monitors also inhabit the Northern New Guinea Montane
Forest.
Our new
reported localities also call into question the minimum preferred temperature
range of V. salvadorii. Under captive
conditions the species is known to significantly reduce activity levels at
temperatures below 24 ºC (Reh et al. 2021). However,
images from the trail cameras show active individuals at 18 °C and 20 ºC.
Furthermore, the mean annual maximum and minimum temperatures at an elevation
of 1,500 m range is between 24.9 ºC and 14 ºC, according to the PNG Resource
Information System (Bryan & Shearman 2008).
There are
several possible explanations for activity at higher and cooler environment;
(1) individuals can elevate their body temperatures by basking on a tree or in
patches of sunlight on the forest floor to permit activity, and (2) individuals
may move along the ground to escape inter or intraspecific confrontations even
at cooler temperatures (Borja Reh pers. comm.
21.xii.2021). Crocodile Monitors have keen senses that allow them to perceive
and avoid threats. Using the ground is an excellent way to remain undetected,
especially by conspecifics.
Crocodile
Monitors are assessed as Least Concern (LC) by the IUCN Red List (Shea et al. 2016). However, their ecological role within
habitats is not clear, and they should be considered a focal species for
monitoring ecosystem health given their status as apex predators (Simberloff 1998; Sergio et al. 2008; Ray 2015).
New Guinea
is experiencing one of the fastest deforestation rates in the world (Curtis et
al. 2018; Amindoni & Henschke
2020). The increasing trend of habitat loss due to logging concessions is
affecting the primary forest habitat of Crocodile Monitors and other
under-researched species, including those that remain undescribed (Allison
1996; Kraus 2010; Miettinen et al. 2011; Letsoin et al. 2020; PNG Data Portal, 2021). Habitat loss
is an increasing concern for the conservation of Crocodile Monitors. However,
the impact of this threat has not been studied.
Despite its
remoteness and inaccessibility, the Torricelli Mountain Range is suffering one
of the highest deforestation rates on the island due to clearing and logging
(Bryan et al. 2015). Industrial logging persists and is increasing in the area,
with new roads being proposed across the range.
Therefore,
habitat loss must be considered an increasing concern for the conservation of
Crocodile Monitors. The effect of this threat on the viability of V. salvadorii populations remains unexplored. It is thus
critical that significant records and information of unknown species, such as
the Crocodile Monitor, are published to trigger conservation measures and help
protect their area.
Camera traps
have proven to be effective in capturing large monitor lizards (Ariefiandy et al. 2013; Jessop et al. 2013) and may offer a
suitable solution to more effectively describing the distribution range and
behaviour of Crocodile Monitors and many other species that remain understudied
in New Guinea (Thomas 2014). However, modifications to existing protocols –
such as including meat-based baits or lures or deployment of arboreal camera
traps might increase the number of monitors recorded as well as other wildlife
unlikely to be detected at ground level (Gregory et al. 2014; Moore et al.
2021). With an expansion of methods with camera traps and increasing
biodiversity surveys, the TCA aims to increase its’ data collection for
biodiversity via camera traps, phone applications and staff patrols into the
Torricelli Mountain Range.
The present
data highlight the limited information available about one of the top predators
and larger animals in New Guinea. The Crocodile Monitor has been far more
studied in captivity than in wild, where virtually nothing is known about their
biological traits. Therefore, more in-depth field studies are needed to
understand the distribution patterns and the impact of anthropogenic threats in
order to take timely measures to conserve and protect the species in the long
term.
For images - -
click here (for full PDF)
REFERENCES
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