Indigenous communities and subsistence whale hunting

Welcome to Science Sessions, the podcast of the proceedings of the National Academy of Sciences, where we connect you with Academy members, researchers, and policymakers. Join us as we explore the stories behind the science. I'm Paul Gabrelson. For centuries, the Inuvialuit people of Northern Canada have hunted Baluga whales. Settlements on the McKenzie River Delta on the Arctic Ocean provided access to a large population of Baluga's, which have sustained the Inuvialuit year-round for generations. In a recent PNAS article, Max Friesen of the University of Toronto, Alina Lorenzen of the University of Copenhagen, Mikkel Skovrin of Lund University, and colleagues, analyzed Baluga bones from the McKenzie Delta representing centuries of subsistence hunting. Initially looking to see how hunting had affected the genetic diversity of Baluga's over time, the authors found surprising shifts in the ratios of male to female Baluga's harvested over time. Max, what role did Baluga's play in the Inuvialuit culture? So Baluga whales and whale hunting is absolutely central to modern Inuvialuit culture and has been for at least 700 years. These are enormously important both for economic reasons, for social reasons. The meat is shared widely. We can see in major archaeological sites going back the full length that the sites are absolutely packed with Baluga whale bones, indicating that they've been economically important for this long. And in fact, one study I was involved with about 20 years ago showed that over half of all the calories eaten at these sites just came from that one species, Baluga whales. Alina, why are you interested in the impacts of Inuvialuit hunting on Baluga populations? I work with Baluga whales, but more from an evolutionary biology perspective. And so I got in contact with Max just out of interest to see did he have any ancient Balugas. And then Max mentioned that he had these time series samples from archaeological sites that are very close to each other. And so this was a unique opportunity for us to investigate how these populations actually have changed through time, through subsistence hunting. Michael, tell us about your methods, where did your specimens come from and what did you analyze for? So the mittens are just where all the waste from the communities deposited. What is happening in this community is that the more and more deposits are left in the estuary of the McKinsey River Delta, every once in a while they're moving the village further north to have it downstream closer to the ocean. And therefore some of these deposits become sort of a time capsule for what has happened in a certain time period. And then when the archaeologists come in they can sort of dig out the Baluga balance from these mittens and we can use them for a different molecular analysis. We wanted to use genetics and we wanted to sequence the nuclear genome. But then another thing we could do with the genetic data once we had it is we could actually identify the sex of each individual, which then gave us a better insight into some of the ecological processes when we could see how many males were harvested, how many females were harvested in the different time periods. We used to stabilize to open analysis. We can basically say something about the dietary preferences of each individual among the samples. Both the sampling of modern Baluga whales and the archaeological recovery of Baluga whale bones from the past were performed in close collaboration with the Nevea-Aloid. It was actually designed to sort of rescue archaeological sites that were being destroyed due to erosion. What did you find? How did Baluga populations change over the centuries? Around 1200 and 90 to 1440 we saw twice as many males. While in the middle time period which is 1450 to 1650 we saw equal proportions of males and females which show something about either the availability of Baluga or the hunting practices that they're using. Then we saw when we moved up to the time in data to 1870 we see that we again have this two to one ratio between males and females which is really interesting. We also know from the modern heart that we have a four to one ratio between males and females. The modern explanation for this change is that it's conservation issue. So there's thinking if we harvest a female it could potentially have a calf and then that calf would also die if we kill the mother. And therefore it makes a lot more sense to take the males. Males is around 25 to 30% larger than females. If you harvest one individual then perhaps it makes more sense to get the bigger individual. We saw that it is definitely the same population that has been inhabiting this region and has been targeted for 700 years. But then when we looked at the stable isotope results in the first and the last time period when we had differences in the number of males and number of females. We also see that there's differences in the delta 13 carbon values of the true sexist. We see that the males and females are harvested at equal proportions. We see that they also have the same isotope profile. But this means that the lugs are flexible in what they can eat and that males and females don't always eat the same thing. And normally we would consider the dietary niche of species to be fairly stable. But this gives us some idea that maybe diets are changing over time and here we see that males and females are eating different things in different periods. And then in that middle time period they seem to have exactly the same diet. Were you surprised that genetic diversity of belugas was not affected by subsistence hunting? We did not find any change in genetic diversity through time in these beluga populations, indicating that there was no impact at least on that measure by the annuvialiate hunting across the 700 years. Now, had we read down the study, probably I would say we would have targeted another measure of genetic diversity in the moment we did because we actually ran a number of simulations to see would we ever find a decline in genetic diversity no matter how many belugas were harvested. And actually you can harvest almost all of them and still within the timeframe available to us you would not see a decline genetic diversity. Rather than the measure that we did use there are other measures but you need much higher quality data. And so we did not have this available. What else did you learn about past hunting practices from your study? So annuvialiate hunting methods from about 1900 and earlier involved large numbers possibly up to 100 or more high actors going out into the east channel of the McKenzie River when they spotted pods of beluga whales lining up behind the belugas and driving them into the shallots where they could be harvested on mass. If they drive hunting in two time slices and those two time slices have very different sex ratios and the sexes have different isotopic signatures then it's not a change in practice rather it's a change in the underlying ecology. So if we could be certain that the hunting methodology was the same which means on mass you take whatever is available then the shifts in ratio of male to female is due to the underlying ecology and that's somehow impacting the species and we're seeing that with the random sample being harvested of the available belugas. Although almost certainly for the middle slice and the last slice it was the same drive hunting methods so at least those changes should be more or less immune to differences in hunting methods. What are the caveats or limitations of this study? Even though 700 years sounds like a long time it's actually very limited. It's not that many generations it will be more relevant to look at it in a number of generations rather than in years. We were always talking on some levels about sample sizes and this is kind of a constant problem with using archaeological data. I mean archaeologically it is very special there are no other places that you can actually get this kind of numbers of bones of an ancient species but on the other hand you're limited by how many were there at the site. And we actually started off quite well with a relatively large number of sample per time been but then when we started investigating males and females of course that halved the number of individuals per sex and so suddenly we were working with much smaller sample sizes than what we had expected. It would have been great with more samples but this is as good as it gets. What do your results mean about the sustainability of traditional hunting practices? What is unique about the beluga population in this region is that the beluga population is extremely large. It's estimated to be around 40,000 individuals. So harvesting a few hundred every year hasn't had a big impact like potentially which we saw in West South West Greenland in the 1920s and 30s even though they were harvesting beluga's at similar levels then that population were much smaller to begin with maybe only a few thousand or 5,000 individuals. So after harvesting that for 10 or 20 years it was completely extubated. And the beluga hunt over time has been substantial and it's almost impossible to actually estimate the exact numbers landed per year. In the 19th century and earlier it could easily have been 500 or more per year harvested by the major communities in the East Channel. And so in theory, that's quite a few individuals to take out of a population, but this study clearly shows that in the longer term, it was easily sustainable. Thanks for tuning into science sessions. You can subscribe to Science Sessions on iTunes, Spotify, or wherever you get your podcasts. If you like this episode, please consider leaving a review and helping us spread the word.