RETRACTED ARTICLE: Biologically validating the measurement of oxytocin in western lowland gorilla (Gorilla gorilla gorilla) urine and saliva using a commercial enzyme immunoassay

Austin Leeds, Patricia M. Dennis, Kristen E. Lukas, Tara S. Stoinski, Mark A. Willis, Mandi W. Schook

The neuroendocrine hormone oxytocin, which is an important physiological driver of social behavior and bonding, is increasingly being measured in conjunction with behavior to better understand primate sociality. However, no data are available on oxytocin concentrations within the genus Gorilla, even though the members of this genus are of great interest to researchers due to their close genetic relatedness to humans and their tolerance-based social system. The purpose of this study was to validate the measurement of urinary and salivary oxytocin in western lowland gorillas (Gorilla gorilla gorilla) to facilitate future study of the interaction between oxytocin and behavior in this subspecies. The primary validation procedure was intranasal challenge. Elevated oxytocin concentrations were observed in saliva samples taken 15-120 min post-challenge. Urine levels were within the baseline range at approximately 30 and 90 min post-challenge, but elevated levels were observed 24 h post-challenge. No diurnal variation was found in salivary samples taken at regular intervals throughout the day, but morning urine samples had higher concentrations than afternoon samples. In addition, samples were collected opportunistically following three social events: play, breeding, and the death of a conspecific. Following the play bouts, salivary oxytocin was almost three times greater than baseline. Salivary oxytocin was also significantly higher 15 min post-breeding compared to matched-control samples. Following the death of a conspecific, the group mate's urinary oxytocin concentrations decreased by half compared to the baseline period when the group was intact. This study provides a biological validation of the measurement of urinary and salivary oxytocin in western lowland gorillas. These results suggest that urinary oxytocin measurements are suitable for establishing baseline levels, as they represent the build-up of the previous day's concentrations, and salivary oxytocin measurements are suitable for assessing changes following specific events.