Do Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus) Avoid ‘Stressed’ Conspecifics?

The production of glucocorticoids by the hypothalamic-pituitary-interrenal axis of amphibians and reptiles allows individuals to respond to acute stressors, but chronic elevation can have negative fitness consequences. Amphibians offer a unique opportunity to study the potential effects of elevated glucocorticoids, such as corticosterone (CORT), as lipid-soluble glucocorticoids readily pass through the skin and into the bloodstream. Interestingly, glucocorticoids are also secreted and excreted by amphibians to such an extent that relative rates of CORT release have been used to assess the relative ‘health’ of populations. Given that CORT has the potential to be both absorbed and secreted through the skin of amphibians and may have a negative impact on fitness, I attempted to assess the degree to which salamanders could identify ‘stressed’ conspecifics whose CORT levels were experimentally elevated through the use of a dermal patch. Plethodontid salamanders provide a convenient opportunity to evaluate the discrimination of ‘stress’ levels in amphibians because they utilize well-developed vomeronasal organs to facilitate a range of behavior, and their plasma CORT levels are readily manipulated via transdermal delivery. I tested the ability of Desmognathus ochrophaeus to detect and avoid substrates sullied by conspecifics with elevated CORT. The test was conducted via a simple choice experiment in which male and female test subjects were exposed to substrates sullied by an individual with baseline levels of CORT or the same individual with experimentally elevated CORT. Overall, I found that females did not differentially respond to substrates sullied by ‘high-stress’ females or males. Males did not avoid substrates sullied by high-stress males but did spend less time than expected on substrates from high-stress females. The differential response by males toward stimuli from high-stress females was replicated in a second study conducted approximately seven months after the first. These findings suggest that male D. ochrophaeus are capable of discerning among females, but not males, in ‘high-stress’ and ‘low-stress’ states. Female salamanders did not respond differently to substrates based on the stress level of stimulus donors.