How To Assess Stress in Reptiles
This paper considers different methods to measure stress in reptiles, as well as the environmental factors that might lead to stress responses in the first place. There are many factors that could contribute to the stress of different species of reptiles, but this paper highlights capture and living in captivity as stressful situations that cause corticosteroid release in many reptile species. The author uses previously published literature to demonstrate how different levels of stress may result in different physiological responses in reptiles, and describes non-invasive, non-captive ways of measuring stress in reptile populations.
At the beginning of Albert Martínez Silvestre’s 2014 study, he defines stress as “a normal biologically adaptive response of an individual to internal or external stimuli representing a threat to homeostasis,” and notes that there are four types of reactions to stress situations: “(1) behavioral changes, (2) alterations in the functioning of the autonomic nervous system, (3) neuroendocrine responses, and (4) immune responses.” In other words, there are various levels of stress response, and they represent an interrelated system of voluntary and involuntary actions designed to protect the individual from whatever is causing the stress. “When the individual is able to safely increase the distance from the stressor, the stress response does not usually affect the animal’s long-term welfare,” notes Silvestre. “However, if the reptile is not able to respond in an appropriate manner, the stressor may cause negative effects on the animal’s welfare, defined as suffering.” The main types of stress that Silvestre considers are “capture and events surrounding this process,” which would be common to any reptile kept in captivity for whatever reason, but especially in many laboratory settings.
Silvestre notes that “escape is not always possible, particularly for captive animals living in a confined area. […] If the stressor persists, the individual may show abnormal nonfunctional behaviors. These “displaced” behaviors may help the animal face the psychological aspect of the stressful event and also reduce the full effect of its physiologic response. […] Reptiles that are progressively and chronically stressed may be predisposed to obesity and hepatic lipidosis. Conversely, acutely or intensely stressed reptile species are predisposed to emaciation, immune depression, and reproductive difficulty.” Apart from observing such behaviours in a controlled setting, since such a captive setting would likely cause further stress, how else can stress levels be measured? Silvestre explains that “problems associated with stress-related increases in reptile corticosterone levels can be attenuated by measuring the glucocorticoid levels in the animal’s feces,” and that “fecal sample collection does not require capture or containment of the animal; therefore, variations in secretion patterns are minimized.” Although such measurements are usually taken from reptiles via a blood test, both fecal and skin samples can be used to measure stress without requiring invasive procedures.
The conclusion of the study states unequivocally that, “reptiles are subjected to many of the same stressors encountered in higher vertebrates, and although it is common to think that reptiles are less likely to be negatively affected by these stressors, it is untrue.” If researchers in the field and in laboratories are not willing to even acknowledge that reptiles experience stress, they are not going to try to alleviate it. “To minimize the likelihood of stress-causing negative physiologic effects on captive reptiles,” the paper concludes, “it is important to understand the different clinical signs associated with stress and the methods for measuring stress in these animals. It is only through raising our awareness of these potential issues that we can minimize the effects of stress on captive reptiles.” Though there is a latent contradiction in keeping reptiles captive but wanting to alleviate their captivity-related stress, the paper offers no further conclusions to resolve this situation.
Original Abstract:
Stress, as an adaptive response of any animal to a stimulus that presents a threat to homeostasis, can occur in reptiles. Yet, many veterinarians fail to recognize the signs of stress in reptiles. In this article, evaluation of reptile stress has been discussed with a focus on the analysis of behavioral changes, neuroendocrine correlation, and biochemical and physiologic effects in reptiles. If stress can be assessed and treated properly in captive reptiles, their health and well-being can be optimized.