Northern Bottlenose Whales
Talk to Hilary Moors and you find out you are talking to a young woman who has found her passion, the ocean and the creatures that live within it. Her research over the past few years has been the northern bottlenose whale, particularly the endangered population found in the offshore waters of Nova Scotia.
As a PhD candidate with Hal Whitehead's Cetacean Research Lab of Dalhousie University in Halifax, Moors is currently employed on contract with DFO via the Federal Student Work Experience Program. For the past six years she has been concentrating her efforts in the field on whale biology and behavior, via both visual and acoustic observation.
Bottlenose whales are unique creatures that appear to be relatively rare worldwide. They're part of a family of whales called "beaked whales" about which not a lot is known. The Scotian Shelf bottlenose whale population is classified as "endangered" under Canada's Species at Risk Act and by the Committee on the Status of Endangered Wildlife.
Although no longer threatened by the defunct whaling industry that is now banned in Canadian waters, they are still at risk from other sources. Because of how these whales are thought to use sound to communicate and navigate, activities that create noise in their habitat are a primary concern. For example, oil and gas exploration on the Scotian Shelf might harm this population through noise from seismic surveying or drilling, although no long-term effects of such noise pollution are established. Entanglement in fishing gear and contaminants such as chemical pollution, oil spills and marine debris, are among other potential threats to the population.
The population that Moors studies lives within relatively deep waters of prominent underwater canyons on the Scotian Shelf - such as the Gully - which is a Marine Protected Area (MPA) about 200 kilometers off Nova Scotia. Regulations in the Gully MPA prohibit the disturbance, damage, destruction or removal of any living marine organism or habitat within the area.
With only about 160 bottlenose whales in the Nova Scotian population, it is critical to keep track of their movements. This has been done in the past through visual observations and photo-identification studies, but Moors' method of choice is acoustic monitoring, which is no easy job on a species that spends most of its time underwater in deep canyons. Ms. Moors explains the process: "What I've been doing is dropping hydrophones - which are basically underwater microphones - down on the sea floor, anywhere from 1200-2000 meters deep. We record whales in the Gully of course because that's one area where we know the population is found. We have also recorded the whales in canyons and other shelf break areas adjacent to the Gully. We are trying to get a more specific measure of how individuals are using these areas over time."
The hydrophones she uses are called autonomous acoustic recorders. They are self-contained acoustic systems with a microphone, battery packs and software to process the acoustic data - all encased in a waterproof casing that can withstand high water pressures. They drop the recorders onto the sea floor, and they record acoustic data, generally for months at a time.
What they record are bottlenose whale echolocation clicks. When the whales feed, they make a very quick click sound, and they do this in a pattern and frequency range that's distinctive to bottlenose whales.
Moors notes, "When I have a whole bunch of recorders out, they give me an idea of which areas the whales are using more and their relative abundance in different areas. The acoustic data basically tells me when a bottlenose whale is within the area. And it also gives me an idea of the relative number of whales there, so I know which areas where there appear to be more, or less, bottlenose whales. Although we can't yet identify precise numbers using the acoustic recordings, group sizes from visual studies have ranged from one to twenty animals."
There are a number of ways to retrieve the recorders. Ms. Moors explains: "One system is where the recorder itself is positively buoyant and it is attached to weights with a wire. And when I send an acoustic signal it initiates a current that goes through that wire, which in turn causes it to corrode away. And up the recorders pop. With another type of system I use, you send an acoustic signal that causes the pin that's holding the recorder to the weights to retract, and then it releases from the weights."
Among the substantive results from Moors' work is confirmation that not only are the whales found in The Gully year-round, but also that they are feeding within and between the canyons nearby.
For her PhD work, Moors tried to put the hydrophones out twice a year so that they could get data from both summer and winter months, with recordings from almost three months at a time. Moors is continuing this work with DFO, now using systems that collect data for six months or more.
Says Moors, "It's really difficult to get out there in the winter months, and the vast majority of the data that's ever been collected on the whales has occurred in summer, particularly July and August. We didn't have a really good idea of what was going on in winter but now we know they're out there feeding in winter as well." This work has shown that the whales are a resident population, rather than a migrating one.
However, they still don't know a lot about the reproductive habits of the bottlenose although at the moment, they think the gestation period is about two years.
The whales feed principally on Gonatus (or armhook) squid. It is believed that the canyons are somehow acting to accumulate or attract squid, and that's why the whales are there. The supply must be plentiful to support the whales year round; however a missing piece to the puzzle is knowledge about the distribution and abundance of these squid on the Scotian Shelf. Scientists have been unable to catch more than a handful of these squid in the Gully, and therefore there is no hard evidence yet that can confirm that there is a large number of these squid in the canyon.
Serendipitously, the acoustic work can tell the researchers a lot about other whale species, as well as potentially about fish species, that are in the area. The other thing they can monitor is noise generated by ships and seismic activity. This is an important consideration given that noise can travel great distances, even from beyond areas protected by current regulation.
As to identifying actual numbers of animals, Ms. Moors notes that the acoustic monitoring she has been doing is not the best method to use. She says, "One thing that's going on right now is that Hal Whitehead is updating the population estimate which hasn't been done for a number of years. So he's looking at revising the numbers based on recent photographic studies to see if things have changed. Are the numbers still stable, or are they going up or down?"
From an international perspective Ms. Moors also points out that the Canadian work is one of the longest-term, most in-depth studies on any beaked whale species worldwide, and in fact Canada is in a leadership position when it comes to the study of northern bottlenose whales.
As to the importance of this work she says, "I think it is critical because we're dealing with both an endangered population of whales, as well as a Marine Protected Area, and we want to be able to monitor both. Both need to be protected for the future, making sure we humans are preserving these vital components of the marine ecosystem for generations to come."
That is undoubtedly a sentiment that most Canadians would agree with.
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