It is not what you know, but what you don't know:Genetic analyses reveal a small unknown eastern North Atlantic breeding population of humpback whales

Humpback whales in the North Atlantic are known to winter in the Caribbeanas well as off western Africa at the Cape Verdes Islands. Photographicmatches have been reported for individual humpback whales photographed innortheastern North Atlantic waters to the Caribbean and Cape Verde Islands.These observations show that humpback whales summering in the NortheastAtlantic winter at both breeding grounds. We genotyped 20 microsatelliteloci in 1530 humpback samples from the Gulf of Maine, Iceland andNorway. Individual-based analyses revealed that about 90% and 50% of thehumpback whales summering in the central and northeastern North Atlantic,respectively, are not part of the Caribbean breeding population but breedelsewhere. The current abundance estimates of humpback whales in thenortheastern and central North Atlantic, as well as off the Cape VerdeIslands, indicates that only a small fraction of the humpback whalessummering in the Northeastern Atlantic winter off the Cape Verde Islands.This observation was further corroborated by estimations of abundanceinferred from the proportion of close kin among the individuals allocated tothe "Caribbean" and "northeastern North Atlantic" breeding population. Inconclusion, our results point to the existence of a second unknown humpbackwhale breeding ground in the North Atlantic, which numbers substantiallyfewer individuals than the Caribbean breeding population. Past and ongoingmonitoring of abundance in the Caribbean breeding population show thispopulation is increasing. However, the "northeastern North Atlantic"breeding appears to be much smaller and thus locating and monitoring thispopulation need be prioritized