Physiological responses of giant pandas (Ailuropoda melanoleuca) in an assisted soft release protocol as measured by fecal glucocorticoid metabolite concentrations
Authors:   , Castiglioni Anne , Spotila James Robert 
Published: April 2022

The giant panda (Ailuropoda melanoleuca) is listed as a vulnerable species in China by the IUCN Red List. Chengdu Research Base of Giant Panda Breeding (CRB) in Sichuan, China is applying a new approach to the introduction of captive bred giant panda juveniles (< 6 years old) to their natural wild habitat. Assisted soft release (ASR) is a method of wildlife reintroduction that uses transitional pre-release enclosures and human-aided learning opportunities to prepare wildlife for release. At the ASR program site, the Chengdu Field Research Center for Giant Pandas (Panda Valley), giant panda release cubs (< 2 years old) (RC) in the reintroduction program are transitioned through pre-release enclosures and provided with human aided learning opportunities by research assistants. Control panda cubs (CC) are kept in normal zoo enclosure structures. The primary objectives of this study was to (1) evaluate the physiological responses to ASR protocol of giant panda cubs using fecal glucocorticoid metabolites (FGM) as a measurement, (2) determine the effect of visitor numbers to Panda Valley on FGM in the release and control cubs, (3) evaluate the effect of age on FGM concentration in juvenile giant pandas, and (4) to evaluate the effect of a temporary enclosure on FGM in a release subadult female. We collected fecal samples (n =185) from giant pandas over a two-month period and analyzed those samples for FGM concentration using enzyme-linked immunosorbent assays. There was a significant difference in mean FGM concentrations between panda cub groups during the October 12 to November 29 study period (F1 = 13.05, p = 0.00). October 12 through November 1 was a time of varied exposure to new environments. November 1 was when more consistency was introduced into the cubs daily schedules. This cub group significant difference in FGM concentration suggests that the cubs were physiologically responding to the variation that occurred during this time period. The response could be due to inconsistent exposure to new environments, increase in physical activity with protocol transitions, or exogenous factors related to captivity. An analysis of the effect of age on FGM concentrations of juvenile giant pandas found no difference in mean FGM concentration between the subadult and giant panda cub groups (F2 = 1.03, p = 0.42). Changes in visitor numbers had no effect on FGM of giant panda cubs at Panda Valley (F1 = 0.09, p = 0.77) (F1 = 0.32, p = 0.58), although month had a significant effect on release cubs FGM concentrations (F1 = 6.07, p = 0.02). A subadult female showed a significant difference in FGM when she was housed in a temporary enclosure compared to when she was placed back into her previous semi-wild enclosure (F1 = 15.86, p = 0.00). Overall, results showed that giant panda juveniles responded to an assisted soft release protocol physiologically, and showed signs of stabilizing FGM responses over time. These findings provide information that can aid in evidence-based management of giant pandas in captivity and in an introduction program.