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Song silenced

Mating dance: male humpbacked whales show off their tails when they sing

renata sousa-lima / ufmgMating dance: male humpbacked whales show off their tails when they singrenata sousa-lima / ufmg

Between July and November the National Marine Park of Abrolhos, on the south coast of Bahia, becomes a stage for the reproductive activities of some 3000 humpbacked whales (Megaptera novaeangliae). Boats with tourists visit them,  between 4000 and 5000 people a year, a sign of the curiosity that these enormous aquatic mammals arouse. Biologist Renata Sousa-Lima, now at the Federal University of Minas Gerais (UFMG) and associated with the Humpbacked Whale Institute, has shown that the activity may be harmful. In partnership with North American, Christopher Clark, from Cornell University, she used recorders that specialize in capturing sounds in water to monitor the whales. The results that were published in April, 2008 in Canadian Acoustics and will be included in a future edition of Park Science, show that males do not handle competition from boats well when they are singing to attract females. Of the nine males monitored four moved away and stopped singing when the boats approached. The other five kept on singing, but also moved away. The observation is worrying: it’s possible that the situation favors the most fearless males, who in getting used to the boats, may be more subject to accidents. More detailed studies may help define a level of traffic that does not upset the whales’ reproduction.