Non-invasive Sampling Strategy for Monitoring Free-ranging Mountain Gorilla (Gorilla berengi berengi) Fecal Corticoid Excretion in Bwindi Impenetrable National Park, South-Western Uganda

Health monitoring of the critically endangered mountain gorilla (Gorilla berengei berengei) as one of the strategies for their conservation requires establishment of non-invasive methods that do not interfere with their natural behaviors. Therefore a fecal sampling strategy was established for use in assessing their adreno- cortical activity non-invasively by investigating corticoid distribution along the fecal strand, possible existence of fecal corticoid excretion rhythms and environmental effect. Fecal samples were collected from nests and along the trails, preserved in 99.7% ethanol and analyzed using validated ICN RIA. The results revealed that gorilla fecal corticoid concentrations increased till 72 h after defecation and thereafter began to decline towards the original levels. At 60 h the corticoid levels began showing significant difference (p 0.05, SC; p = 0.65). There was a strong similarity (SC = 0.79 and ICC = 0.75) between corticoid concentrations of previous night nest and morning trail fecals; supporting the assumption among field workers that gorillas defecate in the nests early morning just before they leave their nests. No difference (S; p>0.05) in corticoid levels among the fecal strand sections was observed. Thus corticoids measured from any section of the firm fecal strand up to 60 h post-defecation effectively represent the non rhythmic fecal corticoid excretory profile, offering the best non-invasive and non-intrusive sampling strategy for study of corticoids in this species.