The threat of discarded food and drinks containers to monitor lizards

Abstract

Zdunek, P. and Kolenda, K. 2022. The threat of discarded food and drinks containers to monitor lizards. Herpetological Bulletin 161: 28-30
___________________________________________________________________________________
The aim of this note is to show that littering is a serious threat to monitor lizards. We present 30 cases where varanids got stuck inside discarded beverage or food containers. These include eight species of which Varanus acanthurus was the most common. The accidents took place in at least six countries. The most common traps were drink and food cans. In five containers lizards were found dead.

Full text

28 Herpetological Bullen 161 (2022)
INTRODUCTION
Monitor lizards (family Varanidae) have a wide distribuon
in the tropics and sub-tropics including Australasia,
south and south-east Asia, Africa, and the Middle East (Koch
et al., 2013; Auliya & Koch, 2020). They have an important
role in ecosystem as predators, scavengers, and creators
of microhabitats for other animals (Doody et al., 2021).
Typically, monitors are big lizards and the family includes the
largest living lizard, the Komodo dragon Varanus komodoensis
whose adult males measure up to 3.1 m and weigh up to
100 kg (Jessop et al., 2006). However, there are some small
species, e.g. Varanus sparnus the adults of which may have a
body length of only 23 cm and mass of 17 g (Koch et al., 2013;
Auliya & Koch, 2020).
Only 14 of the 68 species listed by IUCN are considered to
be of conservaon concern although 10 other species are Data
Decient (IUCN, 2021). Currently, the major anthropogenic
threats to monitor lizards include the degradaon of their
natural habitats, uncontrolled tourism, and pet trade (Koch et
al., 2013; Zdunek, 2019; Arieandy et al., 2021). Locally, road
mortality may also limit their populaons (Hasngs et al.,
2019; Ayob et al., 2020). Moreover, monitor meat is traded
and consumed as a novelty food, a tradional remedy for a
range of ailments (skin diseases, eczema, asthma, blindness),
as an aphrodisiac (Uyeda et al., 2014; Nijman, 2015; Zdunek,
2019), and there is sll demand for monitor skin from the
leather industry (Boscha et al., 2020). Progressive global
warming may also cause a decrease in their habitat patch
occupancy (Jones et al., 2020).
It is well known that many monitor lizards exploit urban
habitats, especially rubbish dumps, which provide food
(Kulabtong & Mahaprom, 2015; Karunarathna et al., 2017).
Indeed, such liered areas are characterised by higher
populaon abundance compared to undisturbed habitats
(Uyeda, 2009; Jessop et al., 2012). Although feeding on
organic waste can improve the lizards’ body condion and
reduce the parasite load (Jessop et al., 2012), availability
of such food alters their behaviour and presents them with
many threats. Associaon with rubbish dumps impacts some
important aspect of monitor biology including - sex rao
(male-biased; Jessop et al., 2012); movement paerns by
reducing species home ranges (Stanner & Mendelssohn,
1987); increased antagonisc interacons and social
hierarchy (Uyeda et al., 2015); reduced ospring survival due
to cannibalism or predaon (Jessop et al., 2012); and reduce
reproducve success due to high levels of mate compeon
(Jessop et al., 2012). Moreover, feeding on anthropogenic
food waste can lead to internal injuries and consequently to a
slow death (Trembath & Freier, 2005; Gillet & Jackson, 2010).
Another, but sll understudied threat is geng stuck in food
or drinks containers. A monitor lizard may put its head into a
container or enter it completely to eat food leovers or other
animals that got stuck therein before. However, geng the
head out of the container may be a problem, and such an
incident is oen fatal. A recent study revealed that beside
invertebrates and mammals, reples are quite oen exposed
to such danger. Among 77 reple-container interacons, 13
(17 %) concerned monitor lizards (Kolenda et al., 2021).
Herein, we highlight the problem of discarded food/
drinks containers by presenng new observaons of monitor
lizards that we obtained from other sciensts and naturalists
combined with those reported previously (Kolenda et al.,
2021). Full details are presented in Supplementary Materials
(Table 1S) and include a total of 32 cases of monitors stuck
in discarded containers (Fig. 1). Most events occurred in
Australia (18, 56 % of all cases). Observaons were made
on eight monitor species, of which Varanus acanthurus
was the most common (9 cases, 28 %). None of the species
observed were in an IUCN Red List threatened category
although Varanus nebulosus and Varanus similis have not
been evaluated. In six containers (19 %), the monitors were
found dead. In the remaining 26 (81 %), they were alive at
the me of observaon, and at least in 22 of these cases
they were rescued by an observer or transported to a wildlife
rescue. The most common container in which the trapped
animals were observed was drinks cans (18, 56 %), followed
by food cans (12, 38 %), and a single plasc jar (3 %), and an
unrecorded type of container (3 %).
Discarded containers are common lier items in
terrestrial environments (Roman et al., 2020). They pose a
threat to various groups of animals, including arthropods and
small vertebrates as well as large animals such as ungulates,
leopards or bears (Kolenda et al., 2021). By themselves
mortality due to such containers would not be expected
to lead to a populaon decline, but they constute one of
The Herpetological Bulletin 161, 2022: 28–30
The threat of discarded food and drinks containers to monitor
lizards
PRZEMYSŁAW ZDUNEK1,2 & KRZYSZTOF KOLENDA3*
1Associaon du Refuge des Tortues (A.R.T.), 2920 Route de Paulhac, 31660 Bessières, France
2NATRIX Herpetological Associaon, ul. Opolska 41/1, 52-010 Wrocław, Poland
3Department of Evoluonary Biology and Conservaon of Vertebrates, University of Wrocław, Sienkiewicza 21, 50-335,
Wrocław, Poland
*Corresponding author e-mail: krzysztof.kolenda@uwr.edu.pl
hps://doi.org/10.33256/hb161.2830
SHORT NOTE

Herpetological Bullen 161 (2022) 29
The threat of discarded food and drinks containers to monitor lizards
many factors that synergiscally may limit the populaon
size, especially in urban habitats. However, in the case of
the Crically Endangered Bermuda rock skink Plesodon
longirostris, an endemic lizard of Bermuda, discarded
containers are indeed one of the main threats (Davenport et
al., 2001). It should be noted that containers such as boles
or cups are also a potenal trap for reples (for details see
Figure 4a in Kolenda et al., 2021), whereas other garbage
poses other direct threats to reples, e.g. by ingeson or
entanglement (Walde et al., 2007; Strine et al., 2014).
Due to the relave rarity of the above-menoned
observaons, the real impact of discarded containers on
monitor populaons remains poorly understood. Taking
into consideraon reports presented herein, we strongly
encourage conservaonists to pay aenon to this issue.
Workshops on conservaon of wildlife (such as presented
by Bhaacharya et al., 2019) that aim to raise public
awareness should menon the harmful eects of lier on
animals. Suggesons for liming impacts should include - to
implement strict regulaons regarding liering and waste
disposal; to install garbage bins along hiking paths and
ensure that they are emped regularly; and, to engage local
communies in rubbish clean-up acons.
ACKNOWLEDGEMENTS
Our thanks to the following for the use of their photographs:
Owen Gale (Fig. 1A), Ben Campbell (Fig. 1B), Zig Madycki
(Fig. 1C), Nicole Haigh (Fig. 1D) and Paul Vandersar (Fig. 1E).
We would also like to thank Ulysse Boiteau-Montéville and
Brian Bush for sharing their observaons of trapped monitor
lizards, and Chris van Kalken for his help in conrming the
idencaon of some species and all who sent us new
records published in the social media.
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Figure 1. Examples of monitor lizards from Australia with
their heads stuck in discarded drinks cans - A–D. Varanus
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30 Herpetological Bullen 161 (2022)
Przemyslaw Zdunek & Krzysztof Kolenda
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Accepted: 19 May 2022

The threat of discarded food and drinks containers to monitor
lizards
PRZEMYSŁAW ZDUNEK & KRZYSZTOF KOLENDA
Table1S. A list of monitor lizards that were found in discarded containers, AD - adult, SUB – sub-adult, JUV - juvenile, D -
dead, L - live
Species
Life
stage
Dead
/Live
Country
Type
of container
Source/Observer
Varanus acanthurus
A
D
Australia
Drink can
Kolenda et al. 2021
Varanus acanthurus
A
L
Australia
Drink can
Kolenda et al. 2021
Varanus acanthurus
A
L
Australia
Drink can
Brian Bush;
https://youtu.be/2cDWddRjhB0;
access date 02.03.2021
Varanus acanthurus
A
L
Australia
Drink can
Ben Campbell
Varanus acanthurus
A
D
Australia
Drink can
Owen Gale
Varanus acanthurus
A
L
Australia
Drink can
Zig Madycki
Varanus acanthurus
A
D
Australia
Drink can
https://www.exploroz.com/Onthe
Road/Environment/Care.aspx;
access date 02.03.2021
Varanus acanthurus
A
D
Australia
Drink can
Eidenmüller 2021
Varanus acanthurus
A
L
Australia
Drink can
Nicole Haigh
Varanus bengalensis
JUV
L
India
Drink can
https://www.youtube.com/watch?
v=V9864TtY3ho; access date
02.03.2021
Varanus bengalensis
A
L
India
Plastic jar
https://www.youtube.com/watch?
v=NK0Yxic-8sA; access date
02.03.2021
Varanus gouldii
SUB
L
Australia
Drink can
Kolenda et al. 2021
Varanus gouldii
SUB
D
Australia
Drink can
Kolenda et al. 2021
Varanus gouldii (flavirufus
type)
SUB
L
Australia
Drink can
Kolenda et al. 2021
Varanus gouldii
SUB
L
Australia
Drink can
Owen Gale
Varanus nebulosus
A
L
No data
Food can
Kolenda et al. 2021

Varanus nebulosus*
A
L
Malay
Peninsula
Food can
Kolenda et al. 2021
Varanus nebulosus
A
L
Malaysia
Food can
https://youtu.be/37csnfVDJxA;
access date 02.03.2021
Varanus nebulosus
A
L
Thailand
Food can
https://au.news.yahoo.com/monit
or-lizard-helped-getting-head-
120000925.html; access date
02.03.2021
Varanus nebulosus
A
L
Malaysia
Food can
https://www.youtube.com/watch
?v=k28heE7RBEQ; access date
02.03.2021
Varanus niloticus
A
L
South
Africa
Food can
Kolenda et al. 2021
Varanus salvator
macromaculatus
A
L
Thailand
Food can
Kolenda et al. 2021
Varanus salvator
macromaculatus
A
L
Thailand
Food can
Kolenda et al. 2021
Varanus salvator
macromaculatus
A
D
Thailand
undetermine
d type
Ulysse Boiteau-Montéville
Varanus salvator
macromaculatus
A
L
Thailand
Food can
https://www.facebook.com/watch
/?v=822815378270890; access
date 02.03.2021
Varanus salvator
macromaculatus
A
L
Thailand
Food can
https://www.youtube.com/watch?
v=RnlXy7rJ84c; access date
02.03.2021
Varanus salvator
macromaculatus
A
L
Thailand
Food can
https://www.facebook.com/watch
/?v=1204178096408768; access
date 02.03.2021
Varanus similis**
A
L
Australia
Food can
Kolenda et al. 2021
Varanus similis
A
L
Australia
Drink can
Paul Vandersar
Varanus tristis
A
L
Australia
Drink can
Kolenda et al. 2021
Varanus tristis
A
L
Australia
Drink can
Kolenda et al. 2021
Varanus tristis
A
L
Australia
Drink can
https://www.sciencesource.com/a
rchive/Lizard-with-Head-Stuck-in-
Beer-Can-SS2422609.html; access
date 02.03.2021
*initially determined as V. komodoensis, but after detailed inspection and consultation with an expert, we suggest it is V. nebulosus
**initially determined as V. scalaris, however, correct name is still under debate, but according to Auliya and Koch, 2020,
Eidenmüller, 2021 and www.reptile-database.org/[accessed 02-03-2021], it should probably be V. similis

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