Tattoo-like skin disease in the endangered subpopulation of the Humpback Whale, Megaptera novaeangliae, in Oman (Cetacea: Balaenopteridae)

The presence of tattoo-like skin disease is reported in an endangered, non-migratory subpopulation of Humpback Whales (Megaptera novaeangliae) from Oman. We examined 522 images taken during small-boat surveys in the Gulf of Masirah and in Dhofar in 2000-2006 and in 2010-2011. Tattoo-like lesions were detected in regular, good and outstanding images. They appeared as irregular or rounded, light grey marks often showing a whitish outline, and were located on the flanks, dorsum, dorsal fin and caudal peduncle. They could be relatively small to very large and cover up to an estimated 40% of the visible body surface. Over the whole study period disease prevalence reached 21.7% in 60 whales and 16.7% in 36 adults. In this category, prevalence was higher in males (26.7%, N=15) than in females (9.1%, N=11), but the difference was not significant. Lesions appeared larger in males than in the positive female and progressed in two males. Disease prevalence increased significantly from 2000 through 2011 (r(2) =0.998). Advanced tattoo skin disease, with lesions extending over more than 10% of the visible body surface seemed to occur more frequently in 2010-2011 than in 2000-2006, but samples were small. This is the first confirmed report of tattoo-like disease in the Balaenopteridae family and the first time it is documented in the Arabian Sea. The disease high prevalence, its increase over time and its progression in some individuals are of concern.