bowhead whale Whales are the longest-lived mammals on Earth Earth Some people live hundreds of years. What’s more, Inuit hunters observed the whales breaking through more than half a meter of ice – ice strong enough to support a fully loaded semi-trailer. The narwhal’s range overlaps with that of the bowhead whale Arctic. The narwhal is the legendary unicorn at the center of Norse mythology due to its unique tusks.
Yet despite their iconic status in the eyes of many, these two massive creatures have faced centuries of violent persecution by human commercial whalers. The bowhead whale, in particular, was prized from 1540 to the 20th century (a period that lasted nearly 400 years) for its blubber, oils, bones and filter-feeding system.
In 2007, a bowhead whale in Alaska was found with harpoon fragments in its body, reminding people of this exploitative practice. Originally cast in the late 1800s, this relic of a Massachusetts whaler represents the long-term impact of commercial whaling on individual animals and their populations.
As these species recover from the impacts of commercial whaling, they now face a new challenge: climate change. The Arctic is warming at nearly four times the global average, bringing profound changes to the region’s ecosystems. Species that have adapted to living in these extreme conditions, such as polar bears, Arctic seabirds and Arctic fish, must now adapt to climate change or perish.
adapt or die
One way organisms adapt to climate change is through adaptation. Adaptation is a concept with a long history in biology. Its central theme is that organisms must adapt to their environment, usually through evolution.
Adaptation depends largely on the genetic variation present in a population because variation provides the raw material for evolutionary change.
However, if you remove large numbers of individuals from a population through hunting, habitat loss, or other factors, you eliminate genetic variation. In this way, hunting and habitat loss directly hinder species adaptation.
Has commercial whaling affected genetic variation in Arctic whales? That’s the question we’re going to answer for bowhead whales and narwhals. Our goal is to understand how historical developments in both species may affect their ability to cope with climate change in the future.
This work is a collaborative effort. Our team is at University of Manitoba Work alongside Inuit subsistence hunters, Assiniboine Park Zoo, and Fisheries and Oceans Canada researchers. We work together to uncover the genetic legacy of centuries of commercial whaling and its impact on the resilience of these iconic Arctic species.
amazing impact
Focus on Eastern Whales Canadian Arcticwe look for changes in the effective population size (the number of individuals contributing to the population) over thousands of generations for each species. The results were immediately shocking.
We observed a dramatic decline in the effective population size of bowhead whales concurrent with commercial whaling, a clear indication of the industry’s impact on their genetic diversity. In contrast, narwhals did not show a similar decline.
These patterns are consistent with historical records showing that commercial whalers primarily target bowhead whales. Surprisingly, the narwhals in our study had much less genetic variation than bowhead whales. We believe that if bowhead whales and narwhals started out with similar levels of variation, they would now have less genetic diversity than narwhals after experiencing more intensive fishing.
It turns out that each species does not start out with similar levels of genetic variation.
About 2.5 million years ago, both species experienced a decline in effective population size, which was more pronounced in narwhals. This decline may have been caused by an ice age, which may have been caused by “nearby” supernova explosions that destroyed the Earth’s ozone layer.
Regardless of the cause, our study shows that narwhals in our study area had much less genetic variation than today’s bowhead whales.
The future is uncertain
What does this mean for climate change adaptation? Unfortunately, the prognosis is concerning.
Narwhals have less genetic variation, but bowhead whales also fare poorly. Commercial whaling has reduced the effective population size of bowhead whales by more than tenfold, putting them at risk of further reductions in genetic variation in the future. Although bowhead whale numbers have recovered, numbers are likely well below pre-whaling estimates.
Urgent conservation actions may preserve remaining genetic variation, allowing bowhead whales to partially recover and hopefully withstand the worst impacts of climate change. Although Canadian Arctic narwhals may not be at imminent risk due to their low genetic variation, they still need to be protected due to their limited ability to adapt to changing environments.
The time required to establish genetic variation is much longer than the time required to lose it. Just as a harpoon thrown in the 1800s was found embedded in a bowhead whale in 2007, the legacy of past commercial whaling has profoundly shaped the genetics of today’s bowhead whale population. This history will continue to suppress genetic variation millenniumposing long-term challenges to the conservation of this species.
Fortunately, both narwhals and bowhead whales are federally protected in Canada. At the same time, intense commercial whaling has largely ceased. Having said that, the effects of climate change are accelerating, especially in the Arctic.
Bowhead whales and narwhals illustrate how past events, human behavior, current challenges and future threats intersect to shape Arctic biodiversity. The lessons we learn from narwhals and bowhead whales connecting the past to the present can and should help protect the biodiversity of all species as they strive to adapt to climate change.
