Reptile Research and Studies on Cognition and Behavior

Reptiles are often regarded as less intelligent compared to mammals and birds, but significant research has recently been conducted on reptilian cognition. This review reveals that reptiles are capable of complex experiences and states, including pain and anxiety.

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Indicative behaviours like hiding, retreating or avoiding a food source can also be seen as signs of suffering, but are often overlooked. This needs to change.

Genetics

A major goal of reptile research is identifying the genes that control particular traits. For example, a researcher recently identified the gene responsible for piebald coloration in the Burmese python (Python regius). This information can help breeders produce snakes with a wide range of beautiful colors. The researchers also hope to learn more about the evolutionary history of reptiles by analyzing the rearrangements that occur in their chromosomes. This work will enable scientists to reconstruct the most likely chromosome arrangement in common ancestors of different reptile lineages.

Molecular cytogenetic techniques, such as chromosome painting and genome mapping, can help reveal the evolutionary history of reptiles by comparing DNA from different species. The resulting chromosome-based phylogenetic tree will be helpful in understanding how genomes have changed over time, and will also help identify genes that may have been involved in the process of reptile speciation.

Another aspect of genetics that has received much attention is the role of environment in influencing phenotypic expression. For example, the sex reversal observed in half-smooth tongue sole ZZ embryos exposed to high temperatures is due to an epigenetic change. In the future, epigenomic studies of reptiles will help establish causal links between environmental conditions and developmental outcomes.

A reptile’s cryptic lifestyle can pose difficulties for the development of genetic tools useful for examining population structure and microevolution. However, next-generation sequencing technologies are allowing herpetologists to overcome this challenge. For instance, cloacal and buccal swabs are now a reliable source of DNA for molecular cytogenetic analyses.

Habitat

Amphibian and reptile species provide a number of ecosystem services to human societies that are critical to well-being. These benefits include supporting services such as nutrient cycling and bioturbation, regulating services such as biological pest control and seed dispersal, and provisioning services including food and raw materials. Despite this importance, a relatively low proportion of studies have investigated these interactions (AmphibiaWeb 2021). Additionally, most studies focus on amphibians and reptiles from North America and Europe, which is largely due to the relative occurrence of these taxa within the studied landscape.

The distribution of reptile species is strongly influenced by climate variables and by landscape structure, with over 80% of species responding positively to at least one of these factors. Among landscape structure variables, the extent of native vegetation had the highest influence on the distributions of 80% of species. The distributions of two species, Lerista bougainvillii and Tiliqua rugosa, were also strongly influenced by the landscape shape.

On average, reptile abundance was one-third lower in modified compared with unmodified habitats. However, responses varied widely across families and exhibited no clear phylogenetic signal. Reptiles tended to respond more negatively to landscape modification that involved the addition of roads and agricultural land use, but less so to changes in landscape structure, forestry practices, patch size reduction, grazing and plantations.

Diet

Reptiles play vital roles in terrestrial, semi-aquatic and marine ecosystems as apex predators1, seed dispersers2, and opportunistic feeders. However, detailed knowledge of reptile diets at the species level is limited3,4, largely due to the difficulty of obtaining adequate samples from wild-caught or captive-bred animals5.

The teeth of a reptile can provide clues about its natural food sources through a process known as microwear texture analysis (DMTA). DMTA evaluates the three-dimensional, sub-micrometre scale textures created on tooth surfaces by interactions with abrasive foodstuffs. Increasingly rough textures are associated with a diet of vertebrates, while smoother textures indicate an invertebrate-dominated diet.

DMTA has been used to infer diets in modern and extinct lepidosaurs, but is not applicable to archosaurs (which includes dinosaurs). Moreover, the dental anatomy and functional morphology of both groups differ from each other in several ways, which may weaken the relationship between microwear texture and dietary guilds.

Nevertheless, recent work has shown that a simple DMTA approach can be used to identify dietary characteristics of reptiles. For example, DMTA of the teeth of Crocodylus porosus and Varanus rudicollis revealed that they consume ‘harder’ invertebrate consumers with hard exoskeletons, such as crustaceans and shelled gastropods. In contrast, the teeth of Gavialis gangeticus, a piscivore that feeds on fish, exhibit the smoothest microwear textures. This may suggest that the’softest’ invertebrate consumers have a less disruptive effect on tooth surfaces than harder foods.

Behavior

Reptiles have a variety of behavioral responses to different stimuli. These behaviors can be divided into two categories: passive and active. Passive behavior consists of escape, avoidance or hiding from a threat while active behaviors involve confrontation and conflict resolution. The ability of a reptile to respond appropriately to predators is highly dependent on species and habitat.

Reptilian behavioral patterns also change as they age. Sexually motivated behavior, for example, can lead to fighting among males of the same species. This type of behavior is highly undesirable in captivity, and can lead to severe injuries or even fatalities. Similarly, a reptile’s food preferences may shift with age. It is important for caretakers to know how these changes affect a reptile’s nutritional needs so that they can provide the right diet.

Some reptiles, such as crocodiles and pythons, can be trained to perform behaviors for entertainment purposes. However, the majority of reptiles do not have the natural instinct to entertain other animals. They also do not typically establish social hierarchies or live in a social group for most of their lives. While some species have been shown to exhibit increased social behavior at breeding time, they usually prefer a solitary lifestyle.

The study of reptile behavior is an ongoing process. More research needs to be done on their cognitive abilities, as well as their capacity for emotional states. It is important to continue to expose the public to the diversity of the reptile world, rather than focusing on the more familiar mammals.