Why do St. Lawrence blue whales pair up in the fall?
Blue whales are reputed to be solitary giants. Yet, in the fall, St. Lawrence blue whales are often seen in pairs. What could explain this behaviour?
To go through the looking glass
Behavioural field observations and photo-identification have been used to document associations between known animals since 1979. In 1988, a biopsy programme began adding another piece of information to help complete the puzzle: gender.
St. Lawrence blue whales begin pairing up into relatively stable couples in late July. The number of stable pairs increases in August, September and October and pairs have been noted as late as December and even into January. With one blue whale in front and the second close behind, the pair, by definition, will remain thus allied anywhere from over a day to weeks at a time. Biopsy samples have revealed that the vast majority of pairs consist of a male and a female. Furthermore, the female—generally larger than her male counterpart—retains the lead; the male maintains its aft position. Pair formation is likely a precursor to mating; given that blue whales mate in winter, fall is the ideal time for a male to “position itself” near a female. Are these pairs still in concert when it comes time to mate? It’s hard to say; winter sightings are practically non-existent. Are pairs faithful from one season to the next? Probably not. This project will be expanded in the future with the addition of acoustic data and the use of radio telemetry to track individual animals.
Project leader :
Martine Bérubé pour l’Université de Californie à Berkeley, Catherine Berchok étudiante au SCRIPPS Institution of oceanography et Véronique Lesage Maurice-Lamontagne Institute (Fisheries and Oceans of Canada).
I want to know more
Visit MICS website