Cortisol, Lactate, and Ammonia Plasma Concentrations Associated with Performance-Based Physical Activities in Bottlenose Dolphins (Tursiops truncatus)

Abstract

Evaluation of metabolic characteristics encompassing short-term performance-based physical activities has fundamental and practical implications to enhance management practices associated with dolphin–human swim interactions. A total of four male and six female bottlenose dolphins (Tursiops truncatus) were involved in the study. All 10 animals were first assigned to a no-swim interaction group as a control group and, after a period of 5 to 77 days of routine training and performance activities, animals were assigned to a dolphin–human swim interaction group. For the swim interaction group, the first or early morning session (0842 to 1005 h) and second or late afternoon session (1354 to 1454 h) involved various degrees of physical activities with and without human participants. For the no-swim interaction group, dolphins swam freely in separate pens prior to feeding and collection of blood samples at corresponding times in the morning and afternoon. Blood samples were collected from both groups within 15 minutes before and after the morning and afternoon sessions. Plasma concentrations of cortisol, lactate, and ammonia were determined using enzyme immunoassay and clinical chemistry techniques. Mean cortisol concentrations were lower after the early morning session (p < 0.021) by 56% and after the late afternoon session (p < 0.004) by 43%. Conversely, and although not statistically significant, mean lactate concentrations were higher after the morning session by 18% and after the afternoon session by 19%. There was also a decrease in ammonia concentrations in the no-swim interaction group during the afternoon session. Regardless of groups and times, there was a temporal negative correlation (r = -0.359, p < 0.0015) between cortisol and lactate such that cortisol decreased (p < 0.05) by 59% from the morning to afternoon and, conversely, lactate increased (p < 0.05) by 68% from the morning to afternoon. While relevance of the inverse relationship between cortisol and lactate requires clarification, the results continue to support the concept that short-term, performance-based physical activities are not metabolically challenging in bottlenose dolphins that are trained and conditioned for dolphin–human swim interactions.