Stationed in Oman, he then began to take an interest in animal life, and for nearly thirty years studied and identified many species, including a species of tahr which now bears his name, Arabitragus jayakari, as well as twenty-two new species of fish (including the eponymous Hippocampus jayakari), two species of snakes (including the eponymous Eryx jayakari), as well as lizards (including the eponymous Omanosaura jayakari) and invertebrates (including the eponymous Hottentotta jayakari). He also made contributions to linguistics, contributing a two-part grammatical sketch and lexicon of Omani Arabic, "The O'mánee Dialect of Arabic", to the Journal of the Royal Asiatic Society in 1889, and a grammatical sketch of Shihhi Arabic, "The Shahee dialect of Arabic", to The Journal of the Bombay Branch of the Royal Asiatic Society in 1904, as well as a collection titled Omani Proverbs in 1900 (published posthumously as a book in 1987). He also contributed to Indian government publications with medical reports such as a "Medical Topography of Muscat" in 1877, and a "Report on the Recent Epidemic of Cholera in Maskat and Matrah" in 1900.[2]