Meeting Abstract
Quantifying individual variation in baseline hormone levels in free-living animals is difficult because circulating levels can change due to the acute stress of capture. While the 3-minute rule has been established for measuring baseline glucocorticoids, there is a lack of such a rule for androgens. Further, infrequently checking traps results in variation in how long individuals experience capture stress. Here, we measured the androgen response to two types of potential capture stressors: restraint and being caught in a net. We performed this study on free-living male wire-tailed manakins (Pipra filicauda) in the lowland rainforest of Eastern Ecuador. First, we passively captured males and obtained a blood sample within 3 minutes. We then restrained them for either 15 or 30 minutes before taking a second blood sample. To measure the androgen response to being caught in a net, 10 to 15 nets were set up, filmed using GoPro cameras and checked every 30 minutes. Video footage was then reviewed to determine the amount of time the bird spent in the net before sample collection. Our first study showed that males exhibited a significant decrease in plasma androgen levels following restraint and the major changes in androgens occurred after 15 minutes of restraint. The results of our second study show support for an effect of capture on androgen levels, however, this effect seems to be driven by individuals with the longest net times (i.e., > 40 minutes). This study presents a new technique (filming the net) that can be used to control for the stress-induced changes in androgen levels caused by capture and informs our understanding of how to accurately measure baseline levels of circulating androgens.
