There has been a long debate on whether cetaceans recognize external chemical compounds in water. Genetically, they lost some taste receptors due to their aquatic adaptations. In contrast, neuroanatomical and behavioral studies have suggested that young dolphins can perceive specific chemicals. In this study, we tested whether young dolphins could recognize fatty acids contained in their mother's milk. We performed mRNA sequencing of the tongue of a 1-year-old Indo-Pacific bottlenose dolphin. Long-chain fatty acid taste receptors were expressed in a V-shaped row of the tongue, which is specific for young dolphins and has taste bud-like structures. The lingual lipase is also expressed in the V-shaped row, which may enhance the release of free fatty acids from triacylglycerols. Notably, the sour taste receptor was nonfunctionalized specifically in Indo-Pacific bottlenose dolphins. We comprehensively qualified the fatty acids in the milk of captive common bottlenose dolphins. Seven saturated and 16 unsaturated long-chain fatty acids were detected. Behavioral tests in captive common bottlenose dolphins showed that a juvenile can recognize the presence of milk in water. These results indicated that young dolphins may have functional fat taste receptors in their oral cavity that detect long-chain fatty acids contained in their mother's milk.

• 西日本新聞『退化したはずが・・・イルカの赤ちゃんに味覚？ 母乳の「脂肪味」感じている可能性』 https://www.nishinippon.co.jp/item/1305563/
• 毎日新聞『イルカの赤ちゃん 味覚ある？ 母乳の「脂肪味」 舌先の突起で感知か 北大などのグループ、可能性示す研究 ／北海道』 https://mainichi.jp/articles/20250115/ddl/k01/040/041000c
• 日経新聞『イルカ赤ちゃんに味覚？ 北大など、可能性示す研究』https://www.nikkei.com/article/DGKKZO86025490T10C25A1CM0000/
• 共同通信社『イルカの赤ちゃん味覚ある？　北大など、可能性示す研究』 https://news.yahoo.co.jp/articles/c96985dfb53f21b39f150b269490edc4918ee093
• 北海道新聞『味覚退化のイルカ、赤ちゃんは母乳識別　北海道大院研究　脂肪味の受容体出現』 https://www.hokkaido-np.co.jp/article/1096183/
• 鹿児島読売テレビ KYT NEWS NNN 『イルカの赤ちゃんは母乳味わう？ かごしま水族館や北海道大学など共同研究 「第６の味覚」に注目 』 https://news.ntv.co.jp/n/kyt/category/society/ky7babdad92ef142418408342592a29bde