One of the biggest attractions of travelling to Antarctica is getting to see wildlife that has no natural fear of humans. But you don’t always have to get up close to appreciate the penguins and seals: some of the most interesting scientific research can be done from a very long way away indeed. We spoke to Dr Michelle LaRue, a conservation biologist and ecologist based at the University of Canterbury in Christchurch, New Zealand, about her work using satellites to study Antarctic wildlife.
Counting by satellite
Your work is based on VHR satellite imagery. What does that mean exactly?
VHR stands for very high resolution, which encompasses satellite imagery with a spatial resolution of less than a metre. This term is a catch-all for any satellite imagery with resolutions ranging from about 30 to 60 centimetres per pixel. It’s a similar resolution to what you can see on Google Earth, where individual cars, trees, and other objects are visible.
How did you come to apply that to Antarctic wildlife?
Michelle La Rue: During my work with the US Antarctic program, I stumbled upon an image of the Erebus Glacier tongue extending into Erebus Bay off Ross Island. I noticed little black dots at the end of the glacier on the sea ice that I suspected were Weddell seals. The identification was possible because they were located on fast ice (ice connected to the Antarctic continent). The ice surface was smooth and flat, making the seals easily distinguishable.
We conducted a pilot study to determine if counting the number of seals on the ice is representative of how many are actually there. And it turns out there that that’s true, so then we proceeded to assess seal populations throughout the continent. It was a very exciting endeavour! Weddell seals became the first species counted using VHR imagery in Antarctica. Concurrently, colleagues from the British Antarctic Survey were using Landsat to locate emperor penguins, and eventually we realised that the same VHR imagery could be employed to identify emperor penguins too.
Weddell seals: remote or up close?
How do you know you had counted all the seals?
With Weddell seals it’s the breeding female population. In November, the female Weddell seals are raising their pups on the ice. And at that time of year, they’re not really doing a whole lot. They hang out on the ice, they don’t really go into the water much – they’re raising their pups.
In Erebus Bay in McMurdo Sound that particular population has been studied since 1967. All of the seals in that population have been tagged. A research team goes out every single year, and puts a cattle tag marker on the flippers of every single pup born in the colony.
It’s an incredible body of work. And that’s the only way that we would have been able to be really certain about what we were looking at.
Traditionally, surveys were conducted either by ground counts, where researchers physically went out to count seals in nearby colonies, or by aerial surveys to cover greater distances. But with only around 70 or 80 research stations on the continent it’s impractical to access all seal locations, making remote sensing the most viable option.
March of the emperor penguins
Do the same principles apply to counting emperor penguins?
Estimating emperor penguin populations demands a more complex approach than for Weddell seals. Unlike Weddell seals, we can’t directly estimate the breeding population by doubling the number of observed animals – we have to employ a more nuanced approach. During the spring we make certain assumptions about the penguins we count on the ice. We focus on adult individuals, considering that some adults may have lost their eggs or chicks, and some may have already left the colony due to foraging activities.
Counting adult animals in the spring provides valuable insights, but it also introduces uncertainties. Successful penguins still raising their chicks might have varied patterns of oceanic foraging, making their presence less predictable. To account for these uncertainties, our research must be cautiously phrased and interpreted.
Thankfully, we have multiple data sources to aid our estimates. We have numerous aerial and ground surveys that serve as comparisons to validate our findings. We also benefit from long-term data collected at Point Geology, the filming location of March of the Penguins. A mark-recapture program conducted there from 1952 to around 1986 provides historical data to help refine our models.
Counting Adélie penguins by proxy
Haven’t you also worked with Adélie penguins?
Adélie penguins are a bit of a different issue, because of course they’re much smaller. I really like them, they have a completely different personality than Emperor penguins. But you can’t see them from space as individuals. One thing they do though is defecate all over the place when they’re nesting. And that guano stain itself can be seen from space. The idea there is that if we can measure the size of the guano stain in contrast to the surrounding rocks where they are nesting, we should be able to make a correlation between the number of breeding pairs that are there with that guano stain. The bigger the guano stain, the more birds. Thankfully, there are also several locations where we have ground counts to make accurate comparisons. So it’s the same idea but with a kind of a twist.
Monitoring indicator species
Why is it important to know just how many Weddell seals or emperor penguins there are?
These animals that we’re talking about are indicator species in some way or another for ocean health.
In the case of Weddell seals, we know Antarctic toothfish are incredibly important prey items for them because they’re so rich in fat and very nutritious. Some of the other species that they might eat like Antarctic silverfish or krill are like a little sweetie, whereas if you can get an Antarctic toothfish, then that’s like a juicy steak. The amount of effort that it takes to catch a toothfish is well worth it for the seal.
The reason that’s important for us is that we also fish for Antarctic toothfish. We’re competing with the seals for their food.
Antarctic wildlife and the climate crisis
Your research also carried a warning about emperor penguins, because current models suggest the species could be quasi-extinct by 2100 under a ‘business as usual’ emission scenario.
The results were shocking and led us to reevaluate our assumptions about emperor penguin populations. One crucial finding was the phenomenon of blinking, where some emperor penguin colonies appear and disappear over time. This revelation, only visible from space, prompted us to question our understanding of their population dynamics. If penguins are not consistently returning to the same spot, it may not necessarily mean population decline.
Collaborating with Stephanie Jenouvrier, we explored alternative modelling scenarios. Instead of assuming penguins always return to the same location, we allowed them to move between existing colonies. One might expect this to yield a more optimistic outcome, with penguins potentially finding new suitable sites. Surprisingly, the results didn’t support this hypothesis.
The findings were disconcerting, leaving us contemplating the implications of the research. But by incorporating new information and empirical data, we can fine-tune the model and gain a more comprehensive perspective on the fate of emperor penguin populations.
Dr Michelle LaRue works with the Penguin Research Fund at the University of Canterbury, which facilitates equipment, travel, and other costs associated with conducting research on penguin ecology, health and conservation in the Southern Ocean. All funds go directly to research, not a penny is spent on overhead.
If you’re tempted to see penguins closer than by satellite, Swoop Antarctica are the polar wildlife experts: Get in touch today and let us help you plan your polar journey.