To validate the use of the biomarker for measuring changes in male reproductive condition, a fecal sample was obtained from three male Peromyscus to determine a basal testosterone level. The animals were then weighed and injected s.c. with 2.5 IU/g hCG in 0.9% sterile saline. ventolin 100 mcg
Fecal samples were collected at 20, 24, and 28 h after injection to obtain the peak testosterone excreted. Four days after hCG dosing, the animals were castrated. Fecal samples were collected from all mice at 6 and 8 days after castration. Animals were weighed and injected again with hCG before a final fecal sample collection the following day.
A preliminary field validation was performed to show the use of the testosterone biomarker on control populations of free-ranging male Microtus californicus through collaboration with Michael Johnson (Department of Civil and Environmental Engineering at UC Davis). Two live-trap grids of 10 X 10 stations had been previously established in the pickleweed marsh at Mare Island Naval Shipyard (Vallejo, CA). A Sherman trap was used twice monthly at each station, and animal number, location of capture, sex, reproductive condition, and body mass were recorded when an animal was trapped. The reproductive condition for males was recorded as abdominal (reproductively inactive) or scrotal testes (reproductively active). Fecal samples were collected during handling, and brought to UC Davis for analysis.