Abstract

Many cetaceans are exposed to increasing pressure caused by anthropogenic activities in their marine environment. Anthropogenic sound has been recognized as a possible stressor for cetaceans that may have impacts on health. However, the relationship between stress, hormones, and cytokine secretion in cetaceans is quite complex and not fully understood. Besides, the effects of stress are probably inconsistent, because the character, intensity, and duration of the stressors are variable. To explore how anthropogenic sounds affect the psychophysiology of cetaceans, the present study compared the changes of cortisol level and cytokine gene transcriptions in blood samples and behaviors of captive bottlenose dolphins (Tursiops truncatus) after sound exposures. The sound stimuli were impulsive pile-driving sound recordings for 30 minutes at different sound levels that likely cause no permanent and temporary threshold shift in dolphins. Six cytokine genes (IL-2Rα, IL-4, IL-10, IL-12, TNF-α, and IFN-γ) were selected for analysis. Cortisol levels and IL-10 gene transcription increased significantly, and IFNγ/IL-10 ratio was significantly lower after a 30-minute high-level sound exposure, indicating the sound stimuli used in this study could be a stressor for cetaceans, although only minor behavioral changes were observed. This study may shed light on the potential impact of pile driving-like sounds on the endocrine and immune systems in cetaceans and provide imperative information regarding sound exposure for free-ranging cetaceans.

*Presenting author