Progression and methodology
My current research is being conducted as part of my Masters with the University of Nottingham - School of Veterinary Science. I am hoping to 'define' movement in Komodo dragons/heavy-bodied lizards, and describe the common appearance of lameness. My hopes are that this will enable the development of a lameness scoring system for use by veterinary professionals and zoo keepers. I am very lucky to have advisors from not just UoN, but the Royal Veterinary College and University of Manchester. I would also like to thank the zoo professionals in numerous collections, who have offered so much of their time and support for this project, such as Dr Frances Baines, Lauren Lane, Shaun Foggett and Ben Sutcliffe.
Development of a quantitative and qualitative gait analysis method in captive and wild Komodo dragons (Varanus komodoensis)
The locomotion of reptilian quadrupeds has been largely studied in smaller species e.g Geckos (Farley & Ko, n.d.; Russell & Bels, 2001; Snyder, 1952; Wang et al., 2015), identifying their two specific gaits and their use of lateral flexion, of the axial skeleton for terrestrial ambulation. In the case of heavier bodied lizards such as the Komodo dragon, little has been described (Borek & Charlton, 2015; Padian & Olsen, 1984). We know due to the sprawling/primitive stance of lizards, they display a serpentine motion of the axial skeleton (Figure 1), this is not required in mammals due to their upright stance and movement within the sagittal plane.
Figure 1 - Komodo dragon Foot placement lateral view - Padian & Olsen, 1984 & Dorsal view personal drawing M. Shackleton
Reviews of captive Komodo dragons showed a range of musculoskeletal, neurological and idiopathic pathologies (Zimmerman et al., 2009). While there is a strong argument that these are probably due to deficiencies within environmental parameters and subsequent hypocalcaemia, musculoskeletal issues are often poorly understood and difficult to manage in a ‘protected contact’ management system employed by zoological collections. Hypocalcaemia is well documented to cause conditions such as hyperparathyroidism and fibrous osteodystrophy, which in turn have physiological effects on muscles, joints and other soft tissue. These physiological effects are further compounded by the behavioural effects of hypocalcemia, such as reduced activity levels, that anecdotally (in reptiles) is believed to cause phenomena such as disuse atrophy (Martinez Silvestre & Franklin, 2019).
Very often, MSK pathology is usually not noticed until severe lameness has become apparent. It is understood that with most cases of lameness, the experience of pain/discomfort can result in reduced range of motion, in order to decrease nociceptive activity (Millis & Levine 1997; Johnston, 1997). Further, reduced movement can predispose joints to shortened ligaments and capsular adehesions, which lead to a feedback loop of reduced activity and pain avoidance, ultimately leading to muscle atrophy (Halbertsma, Van Bolhuis, & Goeken, 1996).
There already exists a wealth of information on how lameness is assessed and ‘scored’ within mammals, facilitating animal/veterinary professionals to identify early signs of lameness, and even monitor the effectiveness of intervention and recovery. The main point of our assessment will be to record the degree of lateral flexion of the axial skeleton, displayed by each individual during locomotion. This is due to flexion being a fundamental mechanism of ambulation, and the numeracy of cervical pathology displayed in captive individuals (Zimmerman et al., 2009).
Approximately 9-10 individuals will be located at BIAZA member collections, 5 UK collections are confirmed, with data collection completed at three, with three individuals. Ideally we will be able to identify individuals who are deemed ‘healthy’, as well as others with history of musculoskeletal pathology; we will hopefully identify this with access to veterinary records or direct communication with keeping staff. For wild data, high quality footage of Komodo dragons will be acquired through online or professional sources e.g. BBC natural history department.
At each participating zoo, video footage will be collected of locomotion within the captive environment, to enable comparison with locomotion in the wild. Go-pros will be positioned above a custom ‘run’ which will be constructed to standardise the surface that all the individuals are recorded/assessed on (to reduce potential variation from substrates, inclines, etc). The same run will be used for each individual, and will contain a grid to provide an additional point of assessment e.g. speed and estimation. Footage will be collected via cameras mounted at laterally/side-on and dorsally/topdown, this footage will then be assessed with the use of biomechanics software (Quintic and Mathis lab) to assess biomechanical aspects of the animal’s locomotion. Wild footage that will also be assessed using the same methods, and an assessment will be made of the gait, both (1) qualitative description/assessment by the keepers and by the veterinarian, and (2) quantitative measurements using Deeplabcut (AI software), in order to assess possible differences in movement/gait patterns between wild and all captive Komodo dragons and between clinically affected vs. unaffected captive Komodo dragons. The data will assessed with the use of the biomechanics facilities at MMU Under the supervision of Dr Christine Brassey.
Figure SEQ Figure \* ARABIC 2 - Camera placement for data collection
This data should allow us to identify signs of ‘abnormal’ movement or lameness in Komodo dragons, using both qualitative and quantitative measures. This will also help to establish a formal measure or scale for assessing gait/locomotion in Komodo dragons, similar to those used for assessment of mammalian locomotion/gait. Particular attention will be paid to movement/placement of the limbs, as well as flexion of the axial skeleton, due to sprawling stance of quadruped reptile. Data will be collected under my supervision and with the advice of Dr John Hutchinson (Biomechanics expert at Royal Veterinary College), to develop appropriate methodology.
Data will be collected in both a qualitative and quantitive manner. Firstly, the video footage will help to record and measure the degree of lateral motion within the axial skeleton, the data will be assessed through the use of the AI software. Deeplabcut can be ‘trained’ to autonomously place ‘markers’ (Figure 4) virtually on designated anatomical landmarks (that would usually have to be physically placed on the animal), this will allow the software to track the motion of the landmarks through the data/footage and provide numerical data for assessment. A lateral view of locomotion will also be recorded (Figure – 3), that will allow for assessment of limb motion, that is inextricably linked to axial motion.
As a further point of assessment a ‘lameness scale’ will be created, there currently exists two prevalent forms of assessment in mammals, Numerical rating (NRS) which incorporated a criteria/score that the observer awards the degree of lameness e.g. 0-5, 1-10, or Visual analogue (VAS), which allows for continuous variables, usually in the form of a 100mm line, that the observe may denote a point on that scale. I have chosen to employ a VAS, but rather than to denote simply weight bearing, will be employed to describe the degree of lateral movement within locomotion. This is particularly due to the fluidity of axial movement, and to studies suggesting this method can be more ‘sensitive’ and allows for continuous variables (QUINN et al., 2007).
Figure SEQ Figure \* ARABIC 3 - Lateral view. Khaleesi at Paignton Zoo, responding to commands to target on the run.
Once this data is collected, videos of other dragons will be sent anonymously to other collections, they will be asked to assign a ‘score’ using the developed VAS system, on the ‘quality’ of movement/degree of flexion. This will hopefully allow us to draw from the experience of keeping staff or work consistently with these animals, and serve as a comparative to quantitive data, on our ability to identify ‘normal’ and ‘abnormal’ gait in reptiles.
Figure 4 - Dorsal view – Assessment of lateral flexion. Batu at
Crocodiles of the world, demonstrating the early stages of
lateral flexion in the axial skeleton. Markers demonstrate
points of assessment for spine, green line helps to demonstrate
degree of flexion even within the early stage.