Over 65% of examined cases of whale and dolphin strandings have the most common causes—the human factor and infectious diseases. A study spanning nearly two decades, conducted by scientists at the University of Hawaii at Mānoa (UH Manoa), illuminates the hazards facing whales and dolphins in the Pacific Ocean. It furnishes vital data for better stewardship and conservation of deep-sea inhabitants near Hawaiian shores. The analysis included 272 investigations of strandings involving representatives of 20 cetacean species occurring between 2006 and 2024. Its findings are published in the journal Diseases of Aquatic Organisms. “Dolphins and whales are indicators of ocean health. We must grasp why these animals perish to aid the survival of others,” stated Kristi West, Director of the Cetacean Heath and Stranding Lab at the UH Manoa College of Tropical Agriculture and Human Resources. Primarily—Illnesses Over 18 years, scientists examined more than three-quarters of stranded whales and dolphins to establish the cause of their demise. In the majority of instances (62%), death was linked to sickness, and roughly half of these animals exhibited emaciation from prolonged illness. Infectious agents proved to be a serious threat, impacting 11 different species, including Risso’s dolphins and Longman’s beaked whales. The two most perilous pathogens are morbillivirus and brucella, capable of causing severe damage to the brains and lungs of marine mammals. Toxoplasmosis—a parasite affecting warm-blooded animals and spread via cat feces into the environment—was responsible for the deaths of two rough-toothed dolphins and one bottlenose dolphin. The Human Element The research indicated that 29% of all strandings were connected to anthropogenic injuries. Collisions with vessels presented a considerable risk, resulting in fatal fractures of spines and skulls in seven individuals, including two pygmy sperm whales, two humpback whale calves, one Cuvier’s beaked whale, and two dolphins (a rough-toothed dolphin and a spinner dolphin). Entanglement with marine debris and fishing gear was confirmed as fatal in several instances, such as: A sperm whale perished because plastic and fishing tackle clogged its stomach. A bottlenose dolphin died after a fishing hook became deeply embedded in its body. The Importance of Public Reports Most dolphins and whales perish at sea, and the probability of their detection is extremely small. Therefore, scientists urged the population of the Pacific islands to report all instances of cetacean strandings.
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