Environmental Drivers of Persistent Humpback Whale Megaptera novaeangliae Feeding Events in a Mexican Breeding Area

Humpback whales Megaptera novaeangliae typically fast for several months in low latitude breeding areas. Here we report on persistent feeding events during 5 wintering seasons between 2013 and 2020 in a known upwelling region of Banderas Bay of the mainland Mexico breeding area. In total, there were 76 unique feeding events documented (group size = 1 to ~100 individuals), involving 201 photo-identified whales, of which 18 were documented feeding in multiple years. The most prolific years of documented feeding in 2017 and 2018 (based on number of reports/individuals photo-identified feeding) followed the strongest marine heatwave ever recorded in the North Pacific. Whales documented feeding in Banderas Bay had significantly shorter mean sighting histories (2.3 yr) than a non-feeding sample (8.7 yr) and were reported to be of small size, suggesting they were predominantly younger whales. Most high-latitude recaptures of Banderas Bay feeding whales were in more northern North Pacific feeding grounds (50.8% were resighted in Russia, Alaska, and northern British Colombia, Canada). A binomial general linear model revealed a significant relationship between the probability of whales feeding in Banderas Bay and sea surface temperature (SST). Specifically, feeding consistently occurred in years of lower than average winter SST (<25°C), associated with La Niña years of the El Niño Southern Oscillation (ENSO). We conclude that feeding of humpback whales is now a predictable occurrence in the upwelling region of Banderas Bay in years that ENSO fluctuations lead to lower regional SST. The magnitude of several years of low-latitude feeding events reported here was likely influenced by climate change induced marine heatwaves that occurred during the study period.

Citation:

Ransome, N., A. Frisch-Jordán, T. Cheeseman, J. Calambokidis, A. Kew, O. Titova, O. Filatova, N.R. Loneragan, and J.N. Smith. 2024. Environmental Drivers of Persistent Humpback Whale Megaptera novaeangliae Feeding Events in a Mexican Breeding Area. Marine Ecology Progress Series 726: 161-179. doi: 10.3354/meps14464

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