Visual Obstruction has No Effect on Post Capture Corticosterone Levels of Juvenile American Alligators (Alligator mississippiensis)
Anecdotal observations suggest that visual obstruction after capture will calm crocodilians, leading many to hypothesize that eye covering reduces physiological stress. However, this has yet to be tested empirically. To investigate this, we randomly divided 20 juvenile American Alligators (Alligator mississippiensis) into two treatments (visual obstruction [VO] and no obstruction [NO]) and took blood samples immediately after capture (baseline) and 30 min after treatment to determine the effects of visual obstruction on alligator corticosterone (CORT) levels. We found that baseline and post treatment CORT levels were similar between both NO-treated and VO-treated alligators; however, CORT levels were significantly elevated 30 min after capture relative to baseline in both NO and VO alligators. Our results indicate that visual obstruction does not prevent or reduce handling stress after capture in crocodilians and that any observed behavioral alterations are independent of changes in CORT levels.Abstract
Binding displacement curves of serially diluted American Alligator pooled plasma (red line) vs. EIA standards of corticosterone (black line). The y-axis denotes the percent hormone bound/total binding measured at 405 nm. The dashed line indicates the 50% binding point.
Effect of Time Point and Treatment on alligator plasma CORT levels. The black circles and black line indicate the influence of Time Point (baseline vs. 30 min) on CORT levels (mean ± SE) in VO-treated alligators. The gray squares and line indicate the influence of Time Point (baseline vs. 30 min) on CORT levels (mean ± SE) in NO-treated alligators.
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