Upcalls and gunshots are music to scientists’ ears

First published in the MLA Newsletter, February, 2012

Much of a North Atlantic right whales’ life is a mystery. Scientists have identified waters off the coasts of Florida and Georgia as winter calving grounds for right whales, but were not sure where the non-pregnant whales went during the winter months. In December 2008, NOAA’s Northeast Fisheries Science Center conducted an aerial survey and sighted over 44 right whales in the Central Gulf of Maine near the Outer Falls region over a ten-day period. The sighting intrigued Jacqueline Bort, a Master’s student at the Collage of the Atlantic, so she decided to study the whales’ use of the habitat for her thesis.

“There were two parts to the project,” explained Bort, now the marine mammal and sea turtle research technician at Virginia Aquarium Stranding Response. “I was looking at seasonal and daily patterns of use of the area and the type of calls the whales used.” Bort, with funding from the Department of Marine Resources (DMR), was looking for two types of calls: up calls and gunshots, both of which are associated with Surface Active Groups (SAG), a mating behavior. “Up calls are contact calls,” said Erin Summers, marine resource scientist at the DMR, who has also been listening to whales in the Gulf of Maine. “Everyone in the population uses this call. It’s like asking, “Where are you” or saying “Here I am.” It’s very common. Gunshots are mating sounds commonly used during SAG.”

A Marine Autonomous Recording Unit ready to go. Photo by Erin Summers.

Bort recorded whale calls using a Marine Autonomous Recording unit (MARU), or pop-up buoy, designed by Cornell University. Inside each buoy, there is a hydrophone connected to a hard drive that records sounds. The buoy is anchored to the ocean floor and can stay there for three to six months, passively recording sounds the entire time. When it is time to retrieve the buoy, a signal is sent to it, telling the buoy to sever its tie. The buoy then pops to the surface. Once the hard drive is removed from the buoy, the recordings are downloaded and digitized.

“There are two ways to use the data,” explained Bort. “You can use automatic detectors [to look for specific calls or whale species], or you can hand browse through each day.” Bort found high call rates between October and February, with a high number of gunshot calls in October, November and December. “Gunshots began to drop off in December and all calls dropped off at the end of February. Then they pick up again in August and September,” she said.

Based on right whales’ gestation period of 13 months, scientists believe whales are mating between October and December. The following December or January, pregnant females give birth to calves off the coasts of Florida and Georgia. Bort’s recordings suggest that non-pregnant whales spend their winters in the Central Gulf of Maine and use the area as a breeding ground. “The next step is to go out and identify the whales to see which individuals are using the habitat and determine if the population includes an age class that is reproductive,” said Bort. “We can also observe the behavior of the whales in the area and collect fecal samples for hormonal information.” If reproductive whales are found in the Central Gulf of Maine, SAGs are observed and hormone levels indicate sexually active whales, the habitat might be confirmed as a breeding ground for North Atlantic right whales.

Dropping a Marine Autonomous Recording Unit over the side can be a tricky proposition as times. Erin Summers photo.

“Right now we are still putting together the puzzle,” said Bort. “I would like to continue to monitor the area to see if it is being used as continuously as we think. There has been some variability in populations in the past.” Bort plans to submit an article about her findings for publication. “It’s up to the federal government as to what to do about protection of the area. But I think it will affect shipping lanes more than fisheries,” she said.

Sound comes in to play even to protect the whales themselves. Cornell University’s Ornithology Lab has a new method to alert ships of right whales in their paths. The Right Whale Listening Network set auto detection buoys in shipping lanes off the north Atlantic coast in January 2008 where they are continuously recording sounds under water. When the software in the buoy detects a right whale call, it sends a cell or satellite phone call to an analyst in the Ornithology lab. The analyst checks the recording to verify that it is a right whale call and then sends out an alert to ships in the area that a right whale has been detected. With 24-hour surveillance, the lab hopes to reduce the number of whales involved in ship strikes, one of the biggest threats to this endangered species.

“Acoustics are being used more often. It’s good for places that are hard to reach by boat or plane in bad weather,” said Summers, who has been working with DMR and COA on various acoustic projects. For more than four years, the DMR has worked with COA students to monitor whales around Mount Desert Island. “Whales show up there every year; there is a high population every summer,” explained Summers. The recorded sounds are compared with boat surveys from the same area to gain better understanding of how many whales use the habitat.“

DMR has also deployed buoys in state waters to look for the presence and absence of whales during the fall. There are no surveys, boat or aerial, documenting the presence or absence of whales in these areas,” said Summers. She said the recordings are done on a weekly basis during the peak of the fishing season to listen for humpback, fin and right whales. “Acoustics is the most cost effective way to monitor the whales and it has one hundred percent coverage of the area. The only downside to acoustics is that it doesn’t pick up any non-vocalizing whales,” she said.
It will most likely be years before there are any conclusive answers about right whales’ use of the central Gulf of Maine. If it is found to be a breeding ground for the endangered animals, the area will likely be protected. “NMFS is looking to update critical habitat for right whales. Right now, they use feeding data and the amount of copepods found in an area [as determining factors]. This might change if [Outer Falls region of the central Gulf of Maine] is found to be breeding ground,” Summers said.