Noninvasive saliva collection techniques for free-ranging mountain gorillas and captive eastern gorillas

This study was designed to develop a simple, noninvasive method for saliva collection: a first step toward developing new diagnostic tests to survey gorillas for infectious diseases. The subjects included free-ranging mountain gorillas (Gorilla beringei beringei) in the Parc National des Volcans, Rwanda, and a group of orphan mountain and Grauer's gorillas (Gorilla heringei graueri) housed nearby in a temporary holding facility. Three collection methods were used to recover saliva from discarded forest food: swabbing, soaking, and washing. Saliva was also collected from orphan gorillas maintained in a captive setting by using dental ropes inside mesh bags. The presence of gorilla saliva in each sample was confirmed by using a salivary s-amylase assay and forensic press test paper. The recovery of gorilla DNA was verified by polymerase chain reaction by using primers specific to mountain and Grauer's gorillas. Of the three collection techniques used to recover saliva from forest food, directly swabbing plant bite marks was the most effective. Wild celery (Peucedanum linderi) provided for the most consistent saliva recovery and is eaten year round by mountain gorillas in Rwanda. This study shows that gorilla saliva can be recovered easily and noninvasively from known individual free-ranging gorillas by collecting pieces of wild celery discarded as the gorillas forage and from captive gorillas by offering them juice-soaked dental ropes inside mesh bags. Both methods can be used to recover gorilla DNA for genetic studies. Saliva collected from free-ranging and captive gorillas may prove to be a useful biologic sample for the development of new diagnostic tests and hormonal analysis.