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First reported predation of a Clouded Monitor (Varanus nebulosus) by the Reticulated Python (Malayopython reticulatus) in Singapore

Authors:
Certain monitor lizards of the family Varanidae are
known to feed on snakes (Karunarathna et al., 2017;
Ong and Sy, 2019; Godwin et al., 2020). In comparison,
predation by snakes on monitor lizards in various
countries has been observed with increasing frequency
(Table 1). Prey sizes and feeding frequencies depend on
size: small snakes feed primarily on small mammals,
and larger individuals choose larger prey (Shine et al.,
1998).
The Clouded Monitor, Varanus nebulosus (Gray,
1831), is a semi-arboreal lizard and one of the most
widely distributed varanid species throughout much of
South and Southeast Asia (Koch et al., 2013; Auliya and
Koch, 2020). There are few observations of predation by
snakes on these varanid lizards: Bringsøe (2020) proved
predation ended with the success of Boiga melanota
(Boulenger, 1896) from Thailand, while Chan (2019)
showed the attempted predation on Varanus nebulosus
by Ophiophagus hannah (Cantor, 1836) in Indonesia.
In both cases, the lizards were juvenile. A documented
case of Ophiophagus hannah successfully predating
on an adult Varanus nebulosus (40–50cm) comes from
northeastern Thailand (Jones et al., 2020).
The Reticulated Python, Malayopython reticulatus
(Schneider, 1801), is a large terrestrial predator that also
occurs in Singapore and is commonly encountered in
the highly urbanised landscape there. It feeds mainly
on mammals ranging from rats, bats, squirrels to large
prey such as wild boars (Devan-Song et al., 2017). This
snake occasionally feeds on varanids, e.g., Varanus
salvator macromaculatus (Laurenti, 1768) (Shine et al.,
1998; Auliya and Abel, 2000; Corlett, 2011).
On 22 July 2022, at 17:12 h, a reticulated python was
observed swallowing a clouded monitor in a drain,
several hundred meters from a human-inhabited area,
at the side of an abandoned road with a secondary
forest on either side in Onraet Road, Mount Pleasant,
Singapore (1.3294°N 103.8328°E; 23 m elevation).
This incident occurred on a day after a heavy downpour.
The capture of the lizard by the snake was not seen.
The Malayopython reticulatus grasped the Varanus
nebulosus by the head and coiled tightly around its
torso (Fig. 1). The size of the lizard was estimated to
be approx. 100 cm total length, and the snake was 8–10
cm in diameter. Both animals did not move during the
12 minutes of the whole observation. The snake likely
swallowed the lizard and moved away as it was not
spotted at the site 24 hours later. The site is adjacent to
a Chinese cemetery and visitors would potentially be a
disturbance to the snake.
Low et al. (2016) reported the predation by a
Malayopython reticulatus of a large lizard (Iguana
iguana) in Singapore, suggesting biological control
of invasive species by the snake. To the best of our
knowledge, this is the first observation of predation
by Malayopython reticulatus on Varanus nebulosus in
Singapore. Observations such as these, even as single
events, broaden the scope of information about the
natural history and ecology of monitor lizards and their
ophidian predators.
Acknowledgements. I would like to thank Thierry Frétey for his
helpful suggestions to improve this manuscript.
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Herpetology Notes, volume 16: 151-153 (2023) (published online on 26 February 2023)
First reported predation of a Clouded Monitor (Varanus
nebulosus) by the Reticulated Python (Malayopython reticulatus)
in Singapore
1,* and Marcel Finlay2
1 Association du Refuge des Tortues, 2920 Route de Paulhac,
31660 Bessières, France; and NATRIX Herpetological
  
2 Nature Society Singapore, 244 Lorong Chuan, Singapore.
* Corresponding author. E-mail: zdunek.komodo@gmail.com;
https://orcid.org/0000-0002-9189-020X
© 2023 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0.
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Monitor lizard species Snake species Age Type of observation Location Reference
Varanus albigularis Naja annulifera Juvenile - Southern Africa Shine et al., 2006
Varanus albigularis Naja nigricincta - - Southern Africa Shine et al., 2006
Varanus bengalensis Python molurus Adult Direct observation* India Mash, 1945
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Varanus bengalensis Ophiophagus hannah - - India Bhaisare et al., 2010
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Varanus bengalensis Naja naja Juvenile - Sri Lanka Karunarathna et al., 2017
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Varanus indicus Boiga irregularis Juvenile Stomach contents Guam Wostl et al., 2011
Varanus palawanensis Ophiophagus hannah - Direct observation Philippines Sy and Ong, 2019
Varanus salvator Boiga dendrophila - Stomach contents Southeast Asia Greene, 1989
Varanus samarensis Ophiophagus hannah - Direct observation Philippines Sy, 2021
* Observation in captivity.
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First reported predation of a Clouded Monitor by the Reticulated Python, Singapore 153
Figure 1. Pictures showing the position (in different angles; A–D) of a reticulated python (Malayopython reticulatus) feeding on
an immobilised adult clouded monitor (Varanus nebulosus). Photographs by Marcel Finlay.
Accepted by Zeeshan Mirza
ERRATA:
Table 1. Predation records for snakes on monitor lizards excluding those described in this work
of Varanus nebulosus.
Varanus
bengalensis
Python molurus
Adult Direct observation India Bhardwaj, 2007
Correct species:
Varanus
bengalensis
Eryx conicus
Adult Direct observation India Bhardwaj, 2007
... Predation by snakes on monitor lizards has been observed a number of times in the past century in various countries (Kurniawan et al., 2018;Zdunek and Finlay, 2023). The Nile Monitor, Varanus niloticus (Linnaeus, 1758) is a semi-aquatic lizard, one of the most widely distributed varanid species in Africa (Spawls et al., 2018;Auliya and Koch, 2020), and is listed as "Least Concern" according to the IUCN Red List (Wilms et al., 2021). ...
... Varanus niloticus is the largest lizard in Cameroon, reaching approximately 240 cm in total length (Haacke and Groves, 1995;Bennett, 1998). A snakes' body size dictates the size of their prey: smaller individuals feed primarily on small animals and large ones on larger prey (Shine et al., 1998;Karunarathna et al., 2017;Zdunek and Finlay, 2023). ...
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