Whale Trust is pleased to announce the release of a collaborative publication reporting humpback whales traveling between Hawaii and Mexico within the same winter season. Two individual male humpbacks were identified in both breeding regions approximately 7 weeks apart. These findings, combined with other evidence of mixing between Mexico and Hawaii humpback whales raise questions about the degree of integration of these populations. The findings are a result of an international collaboration of six organizations - Whale Trust <http://whaletrust.org/>, Whales of Guerrero <https://www.whalesinmexico.com/>, Hawaiian Islands Humpback Whale National Marine Sanctuary <https://hawaiihumpbackwhale.noaa.gov/>, Happywhale <http://happywhale.com/>, Eye of the Whale Marine Mammal Research, and the Departamento Académico de Ciencias Marinas y Costeras <https://www.facebook.com/decimacuabcs/> at Universidad Autónoma de Baja California Sur. The publication is open access, read it in full at this link. <https://royalsocietypublishing.org/doi/10.1098/rsbl.2021.0547>