Humpback whales (Megaptera novaeangliae) attend both Mexico and Hawaii breeding grounds in the same winter: mixing in the northeast Pacific

Abstract

Humpback whales that assemble on winter breeding grounds in Mexico and Hawaii have been presumed to be, at least, seasonally isolated. Recently, these assemblies were declared Distinct Population Segments under the US Endangered Species Act. We report two humpback whales attending both breeding grounds in the same season—one moving from Hawaii to Mexico and the other from Mexico to Hawaii. The first was photo-identified in Maui, Hawaii on 23 February 2006 and again, after 53 days and 4545 km, on 17 April 2006 in the Revillagigedo Archipelago, Mexico. The second was photo-identified off Guerrero, Mexico on 16 February 2018 and again, 49 days and 5944 km later, on 6 April 2018 off Maui. The 2006 whale was identified in summer off Kodiak Island, Alaska; the 2018 whale off British Columbia. These Mexico–Hawaii identifications provide definitive evidence that whales in these two winter assemblies may mix during one winter season. This, combined with other lines of evidence on Mexico–Hawaii mixing, including interchange of individuals year to year, long-term similarity of everchanging songs, one earlier same-season travel record, and detection of humpback whales mid-ocean between these locations in winter, suggests reassessment of the ‘distinctiveness' of these populations may be warranted.

The migratory whale herd concept: A novel unit to conserve under the ecological paradigm

“…While automated matching algorithms have dramatically increased the amount of data available to delineate herds, they have also produced data that challenge our understanding of humpback movement and population structure. There have long been rare, documented cases of interchange of animals between feeding areas and between wintering areas in both the Northern Hemisphere (Calambokidis et al, 2001;Darling et al, 2022;Stevick et al, 2006Stevick et al, , 2016Urbán R. et al, 2000), and Southern Hemisphere (Félix et al, 2020;Garrigue et al, 2011;Steel et al, 2018;Stevick et al, 2013). However, the advent of large, integrated databases enabled by automated matching has resulted in an increase in the number of documented movements between wintering areas.…”

“…Specifically, in the past decade humpback whale songs have been observed to be transmitted among wintering grounds within an ocean basin (Darling et al, 2019a;Garland et al, 2011). Darling et al (2019aDarling et al ( , 2022 concluded that these observations are indicative of ocean basin-wide panmixia, on the assumption that they could only result from extensive exchange of singing males between wintering areas. However, though singing was once thought to be largely confined to wintering grounds (Charif et al, 2001;Clapham & Mattila, 1990), we now know that humpback whales sing both on their feeding grounds late in the season and on migration (Clark & Clapham, 2004;Magnúsd ottir et al, 2014;Mattila et al, 1987;Noad & Cato, 2007;Norris et al, 1999;Schall et al, 2022;Stimpert et al, 2012;Tyarks et al, 2021;Vu et al, 2012), providing a mechanism for transmission of songs among winter areas in the absence of direct exchange of individuals between wintering grounds (Garland et al, 2013;Owen et al, 2019).…”

Towards the definition of the humpback whale population units along the Mexican and Central American coasts in the Pacific Ocean

“…The humpback whales from Nayarit, Jalisco, and Colima coasts deserve special attention for management and conservation purposes. Humpback whales from three population units visit this region: (1) the Central America PU, occupying wintering areas off the Pacific coasts of Panama, Costa Rica, Nicaragua, Honduras, El Salvador, Guatemala, and south Mexico (Calambokidis et al, 2008;González-Peral 2011;Martínez-Loustalot et al, 2019Taylor et al, 2021); (2) the Offshore PU, distributed in the Revillagigedo Archipelago and the northwest coast of Mexico including the Baja California Peninsula, with their main feeding areas located in the Aleutian Islands and the north and the western Gulf of Alaska (Darling et al, 2022;González-Peral, 2011;Titova et al, 2017), and (3) the Coastal Mexico PU, distributed in the northern mainland Mexico and the Baja California Peninsula, with the main feeding areas on the US West Coast and British Columbia (Barlow et al, 2011;González-Peral, 2011;Martien et al, 2021).…”

Interchange of Southern Hemisphere humpback whales across the South Atlantic Ocean

“…The development of global networks of research collaborations and citizen science data collection of humpback whale fluke photos, as well as advancements in automated imaging techniques 17 have led to the discovery of numerous instances of humpback whales documented migrating outside of their expected ranges. These records include the detection of whales thousands of kilometers from their expected migratory location [18][19][20] , and include transoceanic movements between multiple breeding grounds 19,21 and between breeding and feeding grounds [22][23][24][25][26] ; the use of multiple distinct breeding grounds in the same season 26,27 ; migrations to areas beyond the known range of their stock 28 ; and feeding in known breeding grounds 29 .…”