August 1, 2012
Endangered Bowhead Whales Sing Again
Brett Smith for redOrbit.com - Your Universe Online
When University of Washington marine biologist Kate Stafford set out to record whale songs in the remote, icy waters off the coast of Greenland, she had no idea that her microphones would pick up a chorus of bowhead whales, potentially signifying a resurgence of the endangered animal.
Stafford detailed the five winter months of nearly 60 unique songs in an article published this week in the open-access journal Endangered Species Research.
The region between Greenland and the northern islands of Norway hardly has the reputation for being a whale hot spot, in fact about 40 sightings of bowhead whales have been reported there since the 1970s. However, Stafford and her colleagues fixed two underwater microphones to the seafloor in Fram Strait and left them there for the length of the device´s battery life–almost one year.
“We hoped to record a few little grunts and moans,” Stafford said. “We were not expecting to get five months of straight singing.”
Stafford´s team positioned the two underwater microphones, or hydrophones, 60 miles apart. From September 2008 through July 2009, the team recorded over 2,100 hours of simultaneous recordings. To conserve battery power and take recordings for a longer period of time, the hydrophones operated similar to time-lapse photography, taking ℠snapshots´ for nine minutes out of every half hour.
Scientists believe that bowhead males sing primarily during the mating season and bowheads are like some species whose individuals sing the same song their whole lives: more than 60 males passed through the Fram Strait. The report also concluded that if each male has a female companion–there may been more than 100 whales who pass through the strait´s icy waters.
If bowhead males sing one song or all males of a population sing a different song each mating season, like some whale species, the catalog of tunes captured by Stafford´s team is impressive by most standards.
“Whether individual singers display one, multiple or even all call types, the size of the song repertoire for“¦ bowheads in 2008-2009 is remarkable and more closely approaches that of songbirds than other“¦ whales,” the team noted in the report.
Perhaps not surprisingly, the whales sang the most during the coldest times of the recording period, when the densest ice concentrations lead to almost complete darkness underwater. Bowhead whales have been known to use their massive heads to break through this ice in search of air or food.
Bowhead whales are the only known baleen whales that have adapted to live year-round in the Arctic. Of the four identified populations, two appear to be recovering from the commercial whaling industry that decimated their numbers from 1600s to 1800s. The Spitsbergen population, which was the focus of this latest study, was believed to be the largest; at one time numbering between 25,000 to 100,000 whales. This population has shown little evidence of recovery and is currently classified by IUCN Red List as Critically Endangered.
According to Stafford, the extensive recordings are good news for the Spitsbergen population and they open the door to new research and techniques designed to more accurately assess the arctic whale´s population size.