Macroscopic Markers of Dolphin Healing at Sea Linked to Immunity

Wound healing has been studied extensively in humans and lab animals, but not in dolphins. Severe human wounds require extensive medical intervention to avoid infection. Yet severe wounds on free-ranging dolphins heal without infection in microbial-infested seas, a compelling distinction. An eye-witnessed shark attack on a yearling bottlenose dolphin yielded 8 years of macroscopic markers on a live recuperating dolphin by known days of healing. In total, 106 healing histories were generated from the author’s 20-year ethological study of free-ranging bottlenose dolphins (Tursiops truncatus) in St. Petersburg, FL, USA. Results show that unaided wound healing at sea involves two consecutive macroscopic pigment patterns, wounds form preliminary seals by 4–8 weeks, and most heal to atrophic scars that remodel for years. Macroscopic markers in live recuperating dolphins show strong matches with macroscopic wound patterns in stranded Fraser’s dolphins (Lagenodelphis hosei), demonstrating links between macroscopic markers and immune activities. This is the first study to link macroscopic markers visible as healing-related pigment patterns to immunity. Macroscopic markers are conservation tools for tracking anthropogenic impacts on increased susceptibility to infection at sea and could lead to novel therapies in veterinary and human regenerative medicine.