Stereotypical Behaviours In Reptiles

Stereotypical behaviours in reptiles are unchanging and repetitive behaviours that have no apparent or discernible motivation and outcome. These abnormal behaviours are seen to be an indicator for negative welfare and a sign improvement in captive care is required. Part of the issue is a restricted understanding of natural biology for many of the species we keep, in correlation to welfare, especially snakes. This can mainly be attributed to the folklore husbandry understanding of minimalistic enclosures (Nagabaskaran et al., 2021). We simply don’t understand what is normal and once these negative behaviours become a habit it is very difficult to entirely eliminate them from the repertoire (Michaels et al., 2020).

Stereotypical behaviours in reptiles occur due to stress and the reptile, we can improve welfare by allowing them to have greater control over their environment and giving them choice (Nagabaskaran et al., 2021). Stress in captivity can be caused by a number of different factors such as artificial lighting, exposure to aversive or loud noises, uncomfortable temperatures, unnatural substrates, arousing odours, restricted movement, reduced feeding opportunities, reduced retreat space, forced proximity with humans, the maintenance of abnormal social groups (such as prehensile tailed skinks (see figure 2) and restrictions on natural behaviours (Morgan & Tromborg, 2007). These can all lead to abnormal behaviours being shown in individuals.

Why these behaviours occur

Abnormal behaviour is present when the animals’ environment is inadequate and does not enable the expression of natural behaviours, this indicates a negative affective state (Breed et al., 2010). The definition of abnormal behaviour is a broad and encompassing term, it is a behaviour which deviates from what is typical for the species (Abee et al., 2014). Being unable to carry out motivated behaviours leads to frustration, self-injury, redirected behaviour, vacuum activities and displacement behaviour, these can all be indicators of poor welfare (Breed et al., 2010).

Welfare is an individual’s ability to cope, current state and is linked to environment, personality and experience (Robinson et al., 2018). A more ethically and culturally accepted definition of welfare not only includes the animals basic and primary needs, but also the emotional, psychological wellbeing and health. Focusing on positive welfare indicators such as play rather than using negative measures such as body condition to determine quality of life (Hewson, 2003). As much as 68% of the cause or encouragement of ARBs are also causal factors of poor welfare (Mason & Latham, 2004). Animals which experience positive welfare act in a natural and ‘normal’ manner as if in a naturalistic setting (Bracke & Hopster, 2006). Scientists split abnormal repetitive behaviours into two broad categories, repeated motor function (stereotypical behaviours) and repeated goal-orientated behaviours (compulsive or impulsive behaviours) (Garner, 2008 in Rose et al., 2017).

These repetitive behaviours without apparent practical function allow the animal to attempt to adapt or cope in an environment that is causing stress, or be linked to a nervous system dysfunction. Although reptiles are less easy to anthropomorphise opposed to other taxa. They share common traits shown in birds and mammals such as problem solving, parental care, play, complex sociality and sophisticated communication (Burghart, 2013).

Case study in false water cobras

A study was conducted on a male false water cobras (Hydrodynastes gigas) (for a example of a false water cobra see figure 3) housed at ZSL. The study was methods to reduce abnormal behaviours through enrichment (Michaels et al., 2020). He was engaging in repetitive undulation movement against the glass front to his enclosure (see figure 4 for example), with no variation to the pattern or location of the behaviour occurring. Despite this, he continued to carry out stereotypical behaviours. The added stimulation such as scent trails and modifications to feeding patterns did not replace the activity budget dedicated to the stereotypical behaviour.

Stereotypical behaviours are thought to be in some capacity inheritable, many environmental and genetic factors may influence abnormal behaviours (Jeppesen et al., 2004). There is a growing body of research which indicates that stereotypical behaviours are heterogeneous and that subtypes are caused by different factors, triggers and therefore treatments will differ (Polcano et al., 2018). If a behaviour has heterogeneous triggers than the treatments all also have to be in order to make a significant impact on reducing frequency (Polcano et al., 2018). Causes can be internal states which is influenced by the captive environment or external factors, the environment creates chronic stress which therefore impacts elicit and sequence behaviour and past experiences such as during rearing when young can cause abnormal behaviour sequencing long after (Mason et al., 2007).

Eventually these behaviours, when lacking reinforcement or a meaning cause learnt helplessness. This is where animals will show little to no activity, failing to express species-typical fundamental behaviours and can lead to anorexia (Torrini, 2022).

Stereotypical behaviours vs abnormal behaviours

Stereotypical behaviours (SB), one type of abnormal behaviours, are repetitive, highly ritualised motor actions which appear to have no function (Burbacher et al., 2008). Confined animals in captivity frequently show SBs (Polcano et al., 2018). The term can be split into two different categories, whole-body motor actions (such as pacing, rocking or somersaulting) and self-directed movements (such as digit sucking and ear or eye covering in primates) (Abee et al., 2014; Robinson et al., 2016).

Reptile normal behaviour suggests not only natural behaviours, but appropriate context and range. In the wild a individual may spend hours in locomotion exploring and hunting, in captivity the locomotion may be less than an hour spent pacing in a small enclosure when food supply is plentiful (Warwick et al., 2013). Animal behaviours have been suggested to be classed in four overlapping categories. Natural, normal, unnatural and abnormal. Natural behaviours are typically observed in the wild (mating, foraging, basking (see figure 5 for basking example) etc.),unnatural behaviours could be normal or abnormal, but also observed in the wild (training and learnt (see figure 6 and 7 for example)). Normal behaviours may be natural or unnatural, but work within context (trained behaviours, enrichment interaction) and abnormal behaviours not seen in the wild and serve no particular function (stereotypies) (Bacon, 2018).

Internal reactions to stereotypical behaviours

Stereotypies have beneficial effects for the animals such as increasing endorphins and preventing or reducing aggression, they are a coping mechanism (Breed et al., 2010). Detecting stereotypies being present allows carers to recognise their care is lacking and encourages change to tackle the situation. Enrichment and providing an enriched environment can help reduce time spent carrying out the behaviours or halt the presentation of these behaviours entirely.

There is a lacking in field-based behavioural observations and research for many species kept in collections, making it difficult to have good comparative information. The other issue is that field observers influence wild behavioural readings by stressing the participants (Warwick et al., 2013).

Examples of reptile stereotypies

Common stereotypies seen in snakes are nose rubbing, edging, glass surfing (see figure 1), excessive interactions with glass transparent barriers, pressing their nose against surfaces and excessive exploration of the environment/habitat (Torrini, 2022). Excessive interactions with ‘invisible barriers’ can lead to facial injuries (see figure 8 and 9).

There is a positive correlation of home range size and the frequency of pacing. This would indicate that particular attention towards enrichment and enclosure design could have a big welfare impact for these species vulnerable to abnormal behaviours. Furthermore some species cope better than others in captivity, poor well-being experienced by some species needs to be addressed and rectified, there is a possible link to poor captive welfare and vulnerability to anthropogenic threats in the wild (Mason, 2010). Other factors that can have an impact include previous experiences, environmental complexity and individuality (Dallaire et al., 2012: Jones et al., 2011 and Tan et al., 2013).

Take away message

The causes of abnormal behaviour in captivity are heterogenous, multiple factors cause frustration or stress in captivity which leads to the animal coping by the expression of behaviours which deviate from natural behaviours seen in the wild. Species kept in captivity are still wild and therefore have behaviour patterns which are innate and are heavily motivated to carry out due to evolution and natural selection pressuring for these traits. Consequently some species are more vulnerable to these abnormal behaviours developing due to genetics, evolutionary niches such as being highly social and cognitive or having large home ranges and complicated ever-changing natural environments. If the captive environment cannot provide and outlet for these behaviours’ welfare is negatively impacted.

There should be zero tolerance to abnormal behaviours and using positive welfare indicators rather than negative it is becoming increasingly important to develop appropriate measuring techniques. Ethically there is a responsibility to improve welfare and prevent poor welfare from occurring. By carrying out meta-analysis of research to this date and then developing heterogenous solutions to tackle the heterogenous causes. Figuring out not only how to halt, but prevent abnormal behaviour.

Acknowledgements

This article was kindly edited by Lori Torrini.

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