Cytogenetic determination of sex among individually identified humpback whales (Megaptera novaeangliae)

Abstract

Using a small biopsy dart, samples of living dermal tissue were collected from individually identified humpback whales (Megaptera novaeangliae) in southeastern Alaskan waters. In vitro culture of these samples provided enough chromosomal material to karyotype 10 individuals. Examination of the sex chromosomes in the karyotypes demonstrated the sex of each of the 10 whales. In two cases, cytogenetic findings verified previous inferences of sex based on behavioral observations. In another two cases, karyotyping allowed the determination of sex when even long-term sighting histories and behavioral observations had been insufficient. For the rest of the whales, sex determination by cytogenetic findings has preceded long-term sightings and will facilitate the interpretation of future behavioral observations. We conclude that in vitro culturing of dermal tissue collected from naturally marked humpback whales, coupled with karyology, promises to be a powerful technique in future studies of the social behavior and population biology of this marine species.