By monitoring the “gunshot” sounds made by male whales, researchers have found a way to accurately identify breeding grounds. And their findings confirmed their fears: a busy shipping lane is also a vital habitat for a critically endangered baleen whale.
With remote acoustic monitoring, autonomous recorders are used to collect sound data for long periods of time without disturbing animals or the environment. The tool helps researchers understand patterns in animal communication, and studying the seasonality of signals allows them to make inferences about behavior and habitat use. North Atlantic right whales (Eubalaena glacialis) produce a variety of species-specific, stereotyped calls. And there are only about 400 to 500 left in existence.
“Part of the answer lies in a loud ‘gunshot’ sound, made by the male whale," Leanna Matthews of Syracuse University says in a press release. “We’re not exactly sure what the gunshot is, but we think it may be a male-to-male antagonistic signal or an advertisement to females.”
During a two-year period, Matthews and colleagues used acoustic monitoring to analyze these gunshots at two locations on the Scotian Shelf, a geological formation southwest of Nova Scotia. They found that gunshot sound production occurred mainly in the autumn and usually between midnight and nighttime -- supporting the hypothesis that right whale breeding season runs from August to November.
And sadly, as expected, the team also found evidence that Roseway Basin, a heavily traveled shipping lane off the coast of Nova Scotia, is a critical habitat area for the endangered species: Throughout the year, more than 30 percent of all right whales congregate there to feed and find mates. The other site they looked at, Emerald South, also showed seasonal increase in gunshot production in the fall, though less overall compared with Roseway.
With further research using gunshot monitoring, researchers hope to track shifts in distribution and changes in mating activities -- information that could ultimately help save the species. The U.S. and Canadian governments have already taken steps to redirect shipping traffic, in response to several fatal collisions with these whales.
The work was published in PLOS One last week.
[Via Syracuse University]
Image: Georgia Department of Natural Resources (GADNR), Permit 15488