Analysis of the behavioral characteristics and plasma cortisol levels in captive dolphins participating in human-dolphin interaction programs

Abstract

We analyzed the behavioral characteristics and plasma cortisol levels in 17 captive dolphins from three Japanese facilities that participated in human-dolphin interaction programs. The behavioral data for each individual were collected on working days using the scan sampling method, and principal component analysis was used to calculate the principal component score of each dataset, which suggested that the behavioral characteristics of each individual differed by facility. Blood samples were collected from individuals who allowed blood to be drawn voluntarily at both pre- and post-working hours to measure plasma cortisol concentrations. Plasma cortisol concentrations did not differ significantly between the pre- and post-working hours (z = 0.918, P = 0.359). The post-:pre-working ratio of plasma cortisol concentration was significantly negatively correlated with training frequency (r = −0.495, P = 0.012), but not with the number of visitors (r = −0.226, P = 0.301). These results suggest that the stress levels and behavioral characteristics of dolphins maintained in marine facilities are more strongly influenced by how they interact with trainers than by the regularity of interactions with visitors.