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The red-backed salamander, Plethodon cinereus

Faheem Nasar, Terri Provost, & Sharon Wise



The Effect of Testosterone on Aggressive Behavior in Male Red-Back Salamanders


Aggressive behavior in some vertebrates is related to circulating testosterone concentrations. Endocrinological studies have demonstrated the importance of androgenic hormones in social behavior, including the establishment of territories. Previous studies have failed to find a relationship between plasma testosterone levels and aggressive behavior in amphibians. The Challenge Hypothesis predicts that circulating serum testosterone levels will increase during periods of increased antagonistic interactions, as may occur during territorial contests. A pilot study at Utica College tested this hypothesis using red-backed salamanders, Plethodon cinereus divided into four treatment groups: resident control, resident experimental, intruder control and intruder experimental. Serum testosterone levels were significantly different between resident experimental and intruder experimental groups. The present study, determined tissue testosterone concentrations in the head, trunk, testes, and tail of seventeen salamanders from the pilot study. Testosterone concentrations were determined by a commercially available radioimmunoassay kit. We predict that testosterone is stored throughout the body for quick release and utilization. If this prediction is true then higher levels of tissue testosterone will be present in the salamanders exhibiting aggressive behavior. Early findings indicate an elevation of testosterone in the head and tail of intruders. Further analysis of behavioral and testosterone data will determine if this study supports the Challenge Hypothesis.
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