Do Reptiles Really Lack Sentience?
Reptiles have become increasingly popular pets around the world. Many people believe that reptiles rely primarily on instinct rather than possessing the rich emotional lives often associated with cats and dogs. As a result, they are often assumed to require little space and only simple enclosures. However, growing research suggests that these assumptions may underestimate the abilities of reptiles.
Sentience is generally understood as the capacity to experience both positive and negative affective states, including pain, fear, and pleasure. Compared with mammals, however, there is still greater uncertainty among the public about whether reptiles possess these capacities. Consequently, their welfare has often received less attention in both legislation and husbandry practices.
Research has shown that people's perceptions of animal sentience are influenced by a variety of factors, one of which is evolutionary relatedness to humans. Because reptiles are more distantly related to humans than mammals, their capacity for sentience is more likely to be underestimated.
These perceptions may also influence the way reptiles are kept as pets. If owners believe their animals cannot experience pain, fear, or pleasure, they may be less concerned about their quality of life, less likely to prevent negative experiences, or less inclined to provide environments that promote good welfare. As a result, some reptiles may unknowingly be kept under poor living conditions for long periods. For example, many owners assume that reptiles are inactive, require little space, and have minimal environmental needs, leading them to be housed in small, unstimulating enclosures.
In fact, current research suggests that reptiles are far more complex than many people realize. Some species display clear social behaviors, and as more studies become available, sociality may prove to be more widespread among reptiles than previously thought. In addition, many species occupy relatively large home ranges in the wild rather than remaining in a single location for extended periods. These findings suggest that many reptiles perceive and respond to their surroundings and may be more affected by environmental conditions than commonly assumed.
To better understand the current state of research on reptile sentience, researchers reviewed studies published between 1999 and 2018. In this review, sentience was defined as an animal's capacity to experience both positive and negative affective states, including basic experiences such as pain and fear, as well as more complex emotions such as grief and empathy.
The studies included in the review covered a total of 50 reptile species, representing only 0.46% of the approximately 10,793 reptile species currently recognized. Most of the research focused on squamates (Squamata), which accounted for 80% of the species studied, followed by turtles (Testudines, 14%) and crocodilians (Crocodilia, 6%). No studies were found on tuataras (Sphenodontia), although the authors noted that this was not surprising given that only two living species remain within the order.
The review also found that although the number of studies on reptile sentience increased slightly between 1999 and 2018, the overall growth was inconsistent. Furthermore, all of the available studies were published in just 17 scientific journals, indicating that reptile sentience remains a relatively new field with limited research.
Although research on reptile sentience is still limited, the available evidence suggests that reptiles are widely considered to be capable of experiencing anxiety, fear, pain, stress, excitement, frustration, and suffering. Nevertheless, compared with mammals, our understanding of reptile sentience remains limited, and many aspects require further investigation.
This gap in knowledge is not unique to reptiles. Birds, fishes, and invertebrates have also received relatively little attention. The authors suggest that people are generally more likely to attribute sentience to mammals because they are more closely related to humans, whereas they may be less likely to do so for other animal groups. This anthropocentric bias may influence both scientific attention and the level of welfare consideration different animals receive. They therefore argue that assessments of animal sentience should not rely solely on intuition, but should instead be based on scientific evidence together with an understanding of each species' natural history.
The pet trade is another area in which reptile welfare deserves particular attention. Whether reptiles are collected from the wild or bred in captivity, they may experience stress, injury, or even death during transport, trade, and subsequent husbandry. Some surveys have found that large reptile wholesalers discard substantial numbers of dead or dying animals each week, highlighting serious welfare concerns within the industry.
Even after entering people's homes, many reptiles may still live in environments that do not meet their natural needs. For example, studies have found that green iguanas and some turtle species show a marked increase in heart rate when handled by humans, suggesting that they may experience emotional stress. However, because they often do not struggle visibly, owners may mistakenly assume that the animals are not distressed.
Selective breeding may also introduce new welfare concerns. One example is the Spider morph of the ball python (Python regius), which is prone to a condition commonly known as wobble syndrome. Affected individuals have difficulty controlling head movements while feeding. In addition to causing physical impairment, the condition may also lead to frustration during feeding.
A number of methods are already available to assess reptile welfare through behavior. For example, ball pythons experiencing pain may delay feeding. However, these behavioral signs are often overlooked by owners, partly because many people still believe that reptiles are incapable of experiencing pain and therefore underestimate their welfare needs.
Future research should continue to investigate negative affective states such as pain, fear, and stress, while also exploring whether reptiles experience positive states such as pleasure and play. Evidence already suggests that some reptiles do engage in play behavior. For example, several crocodilian species have been observed playing with pink flowers in the water, and researchers also found that they appeared to prefer small pink objects over other types of objects.
Such research may help identify the types of environments that promote reptile welfare. Beyond sentience, greater attention should also be given to reptile cognition, including learning, memory, and decision-making. Research in these areas could not only improve reptile husbandry but also challenge the widespread perception that reptiles are emotionless or simply driven by instinct, helping people better understand that reptiles are also animals capable of rich subjective experiences.
（Author: Bai Leng）
Reference：
Lambert, H., Carder, G., D’Cruze, N. (2019). Given the Cold Shoulder: A Review of the Scientific Literature for Evidence of Reptile Sentience. Animals (Basel).
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