Among the 16 individuals tracked during the wet season, eight whales (#20158a, #24642, #26712, #27261, #50678b, #50682b, #7618 and #7926) left Mauritius waters in December heading towards Rodrigues Island (Figs. 2a and 3). Except one, these individuals were all mature females (based on Photo ID, morphology, size and mother-calf association) and showed a synchronized departure from Mauritius. They made a loop eastward of Mauritius before returning at different times. In 2014, only one individual was considered migrant (departure on the 2014-12-25) while in 2018, seven whales initiated their short migration on the exact same date (2018-12-15). The increased distance from Mauritius matched the decrease in SST (extracted at the whales’ positions) for all migrant whales (Fig. 3c,d). Unlike the decrease in SST values at the whale’s locations between December and January, the SST extracted inside the 50% kernel increased for both years from December to January (Fig. 3e,f).