Most vertebrates have testosterone, and have behaviors that are
mediated by this hormone. Testosterone can be helpful to animals,
by enhancing (e.g.) territory acquisition, or harmful, by (e.g.)
causing physiological stress. When male blackbirds are exposed to
other male blackbirds, their testosterone levels change. In order
to understand the impacts of testosterone on male blackbirds,
researchers followed a few individual males, to monitor
testosterone changes after encountering another male. A
pre-exposure measurement was made (in nanograms/deciliter) and a
post-exposure measurement...