This undergraduate dissertation gives an insight into the activities and behaviours of captive common chuckwallas. This reptilian species is found in the United States and Mexico. The study was conducted to improve reptile care as many reptilian species have similar tendencies. It was also intuitiv...
ACTIVITY BUDGETS OF COMMON CHUCKWALLAS (SAUROMALUS ATER)
AT THE NTU ANIMAL UNIT, SOUTHWELL
by
LIAM. T. FRANKLAND
Dissertation submitted in partial fulfilment of the BSc (Honours) Degree in
Wildlife Conservation
2017
, Abstract
The common chuckwalla (Sauromalus ater) is a large desert reptilian, known to annually have a
varying level of activity in the wild depending on environmental factors, mainly temperature,
precipitation and vegetation. Activeness is most prevalent from March to August with inactivity
being from October to February due to hibernation. When active, chuckwallas normally spend most
of their time basking on rocks in the baking sun while displaying low levels of movement throughout
the day. Captive chuckwallas differ from their wild counterparts as they usually exhibit more social
behaviours and activity because of co-occupant stimulation, the same constant range of artificial
heat and protection from predators.
Examination of a common chuckwalla trio’s activity was undertaken at the NTU animal unit, located
at Brackenhurst Estate. From November to January, three captive co-occupants were recorded for
forty sessions each lasting an hour. Reasoning for this was to understand the dynamics of their
activity budgets and behaviour while assessing how humans influenced these factors. 1331
behavioural occurrences were exhibited which covered 13 types of behaviour. Findings found that
humans were not negatively influential on the species as activity was not reduced when they were
present and stereotypical behaviours were a relatively rare occurrence. Locomotion was found to be
significantly superior than resting behaviour because the chuckwallas live in a group and have much
less need to preserve their energy than in the wild. Natural activeness closer to spring was found to
be a plausible explanation for increased activity in January compared to December.
Some limitations were uncovered as there was difficulty in distinguishing some behaviours apart and
recording data at an optimal time was not always possible. Constraints like these can be taken into
account for future studies by being adjusted appropriately. Despite issues indicated, this research
will aid in the expansion of scientific knowledge surrounding all chuckwalla species and many other
reptilians, particularly iguanids and desert lizards. Knowledge covering management of captive
populations, ethology and stereotypical behaviours are some of many areas which will improve as a
result of this study.
, Acknowledgements
I would like to thank my dissertation supervisor, Esther Kettel for guiding me in the right direction
and helping me to grasp certain aspects which I felt difficulty to understand at first. The support
from friends and family has been overwhelming and their help has contributed to this dissertation
massively so I cannot thank them enough. I would also like to thank my course manager, Louise
Gentle for providing extremely intuitive dissertation lectures which aided me in how to write and
structure each section correctly. Any other person who had any involvement with this dissertation
has my upmost thanks and appreciation because without them this study would not have reached
the standard I had hoped for it to achieve.
, Introduction (Chapter 1)
Chuckwallas are a unique large lizard species predominantly residing in the deserts of North America
and Mexico with some species being found only on small isolated islands. This particular species
possesses uncommon reptilian characteristics such as being strictly herbivorous (Nagy & Shoemaker,
1975) and having a significant diversity of distinctive colouration across different locations. They are
a very important ecological species as they perform selective feeding which can alter their
environment profusely. As made evident by Beaman et al. (1997) there are possibly as many as nine
species of chuckwalla under the Sauromalus genus in the family Iguanidae, however only five are
scientifically recognised (Hollingsworth, 1998). Two endemic island species consisting of the san
Esteban chuckwalla (Sauromalus varius) and the angel island chuckwalla (Sauromalus hispidus) are
known in the genus which have five times the body mass of all mainland species (Petren & Case,
1997). The common chuckwalla (Sauromalus ater) has four sub-species including the Western
chuckwalla.
Common Chuckwallas (1.1)
The common chuckwalla which is also referred to as the northern chuckwalla was first established as
a species by Duméril in 1856 (Beaman et al. 1997) and is now considered Sauromalus ater instead of
Sauromalus obesus in more updated studies. The name Sauromalus obesus first made valid by Baird
in 1859 is considered by some to have precedence over the S. ater name due to being in a greater
number of publications (McDiarmid et al. 2002) but for the sake of this report S.ater will be the
chosen scientific name.
Photograph 1.1: Common chuckwalla in Death Valley,
California, obtained from
(http://www.visitcalifornia.com/attraction/lizards, 2018).
Physical Description & Adaptations (1.1.1)
Characterised as a diurnal rock-dwelling iguanid having an
average length of 5-9 inches but can potentially reach up to 16 inches long. The body features a large
flat and stocky physical appearance that possesses a defence mechanism by having folds in the neck
and sides which acts as an adaptation in order to hide from predators by being able to wedge
themselves into rock crevices by means of inflation (Schultz, 2014). During inflation and wedging air
is forced into the lungs causing pulsating contractions resulting in maximum pulmonary pressure
(Deban et al. 1994) to take place. A notable physiological adaptation of the chuckwalla is that it has
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