by Chris Petersen and Madeline Motley
I may not be able to see you, but I can hear you.
You would think that whales are large animals, they have to come to the surface to breathe, so we would be able to know where they are at any time. But often we don’t. The ocean is large, and there are vast expanses where there are not lots of people a lot of the time, at least looking for whales. Earlier this year, researchers led by Jackie Bort (COA ’11) along with other researchers from COA’s Allied Whale, the state’s Department of Marine Resources and the federal National Marine Fisheries Service published a paper in the journal Endangered Species Research investigating what we could learn about endangered North Atlantic right whales, Eubalaena glacialis, in the Gulf of Maine by listening for their calls.
The paper examined calls for a year from underwater acoustic monitors, basically large recording devices on the seafloor that can later be retrieved by signaling them to leave their sandbags behind and pop up to the surface and be collected.
Right whales are a critically endangered species of whale that are known to use the Gulf of Maine (GOM) in the summer, but until recently the main winter population was thought to be in the southeast, off Florida and Georgia, and consisted largely of moms and calves and was considered a calving ground. Where were the males? Work published in 2010 using aerial surveys showed males and some females in the central GOM, but this work is expensive and data collection via planes is often hampered by bad weather. That is where the passive acoustical monitors come in handy. They can spend a year collecting data, and then be retrieved. The only sampled subset of the year, and finding the calls. The authors tried to do this with pattern recognition software, but it kept on calling things right whale calls that weren’t (a 73% false positive rate, meaning that almost three quarters of the sounds the program identified as right whale calls weren’t). So they had to do a lot of listening.
Our favorite line in the paper: “A team of 13 analysts assisted with data from April 2010 through September 2010”. Our interpretation of this line is that if you were a COA undergrad helping out at Allied Whale during this study, you probably have heard more whale calls that you ever thought you would (they are listed in the acknowledgements). In the results they mention that the sub-sampled data set contains about 50,000 recorded whale calls!
The results of all of that listening showed a steady occurrence of right whales in the area September through January. So, what are the whales doing in the Gulf of Maine in the winter? Certainly some of it is for feeding, and the authors cite a paper by Gaskin in 1991 who had hypothesized that some whales stay locally to feed in plankton-rich winter feeding grounds. However, with birthing in the south in the winter, and a gestation period of about a year, this is also the time for mating. The continuous presence of right whales in the central Gulf of Maine during winter months and the types of calls made by males suggests that male advertisement or mating behavior may also be taking place in this region at this time. Females identified by aerial surveys in the GOM in one winter are often found the next winter in the south giving birth. Certainly not a verification of the mating population idea, but it is suggestive.
The research was part of Jackie Bort’s (COA ’11) Master’s thesis, more of the work at Allied whale can be found on their webpage:
Bort, J., S. M. Van Parijs, P.T. Stevick, E. Summers, & S. Todd. 2015. North Atlantic right whale Eubalaena glacialis vocalization patterns in the central Gulf of Maine from October 2009 through October 2010. Endangered Species Research 26:271-280. Doi:10.3354/esr00650
An open access PDF of their paper can be found at: