As Antarctic travel specialists, we know just how much people love penguins. Who doesn’t? They’re animals so ridiculously charismatic that they could have been designed in a laboratory for marketing purposes alone. These scene stealers sometimes leave little room for some of Antarctica’s other wildlife, including its seals – no matter how picturesque they can look snoozing on an ice floe.
But Antarctica’s seals shouldn’t be overlooked. They’re perfectly adapted to their environment and have some truly incredible things to teach us about life in the freezer. To find out more, we spoke to Dr Luis Huckstadt, a senior lecturer at the University of Exeter’s Centre for Ecology and Conservation, about his research in Antarctica, and about how cutting-edge research technology with seals give us extraordinary insights into delicate polar ecosystems.
How did you start working with Antarctic seals?
I did my undergrad and my masters in oceanography at the University of Concepción in Chile, working on the interactions between sea lions and fisheries in central Chile. Antarctica was serendipity – I got a Fulbright Fellowship for the University of California in Santa Cruz to do my PhD on sea lions, but my advisor had just got a research grant to look at the ecology of southern elephant seals and crabeater seals. That was how I got involved with science and pinnipeds (seals) in Antarctica. I think I’ve been down to Antarctica around 15 times now. I’ve worked in the Peninsula but most of my research has been in McMurdo Sound in the Ross Sea.
What makes Antarctica’s seals so interesting to work with?
We have a picture in our minds of Antarctica in the summer, with all its rich wildlife. Most of that leaves when winter begins, but the seals are all permanent residents of Antarctic waters. They’re highly associated with pack ice, and depend on the ecosystem for the entire year.
Seals are big animals with high metabolic rates and high energy requirements, and there are a lot of them because, unlike whales, they went through very little commercial exploitation. They’re important consumers of krill and fish, so they can tell us interesting things about how the ecosystem’s trophic web is structured during the winter when things are colder and there’s nobody else is around.
Can you introduce us to the main species of Antarctic seal?
There are four true Antarctic seals: the Weddell seal, the crabeater seal, the leopard seal and the Ross Seal. To this we can add Southern elephant seals and Antarctic fur seals, which can also be found elsewhere. (for more see Swoop’s guide to Antarctic seals)
Crabeater seals are the most abundant seal on the planet – there are probably upwards of 15 million of them, and they’re closely associated with pack ice – frozen sea ice. Their diet is over 90% krill, and their teeth are beautifully adapted to be used as a krill filter. They’re circumpolar and live in the pack ice and they’re an important flagship species: anything that happens with crabeater seals should give us a picture of what’s happening with Antarctic krill and therefore the rest of the ecosystem.
Weddell seals are a little bit different because they form colonies and aggregate for the breeding season on fast ice – the continuous sheet of ice that’s anchored to the mainland. They’re the southernmost breeding mammal on the planet. I think of them as a generalist species, because they have an incredible ability to adapt to the local ecology of where they live. In the Antarctic Peninsula, some of them don’t move for an entire year, and then you have animals in the Ross Sea or the Weddell Sea that swim for hundreds of kilometres. They have an incredible plasticity that we don’t see in other animals.
Your work uses Animal-Borne Instruments (ABIs) to record what seals are doing. How do these sensors work?
I work in a field called Bio-Logging, which goes back to the 1960s when someone first put a sensor on a seal to find out how long and how deep it dived for. Now we have sensors that can do almost anything you can think of. We use tags that have accelerometers and magnetometers to reconstruct the swimming style of animals as they’re moving through the water column, and we can use cameras to detect what kind of prey they’re eating – even down to understanding how they utilise their whiskers to capture prey and sense their environment.
Seals and sea lions have been very important in the development of these technologies, because they tend to form colonies, so the chances of recovering your instruments are much larger so you can actually get a lot of really cool data by doing that.
How do you attach the sensors?
We glue the tag onto the fur. These seals rely on blubber for their insulation – their fur isn’t really functional, so these instruments will stay on for nearly a year until they go through their annual moult.
We’re very conscientious about reducing any possible impact on these animals – the sensors are around 0.1% of the body mass of the animal. They’re really well designed so they’re hydrodynamic and naturally buoyant. There have been several studies showing that if they’re well-designed, they have a negligible effect on the animals.
What has your research shown us so far?
The data that we collect is mostly movement patterns and diving behavior, but we also measure things like temperature and salinity. I can use those data to understand what kind of cues these animals use to change their behaviour and find prey.
I work mostly in ecology, but I interact a lot with the oceanography community – and one of the things that community has is a huge thirst for raw data, particularly during winter in Antarctica when it’s impossible to take a vessel to waters covered by sea ice. But the seals that we tag are there during the winter, right? So they have an amazing ability to dive and take samples for us, and the tags can transmit most of the data over satellite to look at in the office. We’re pushing this concept of using seals as oceanographers.
We can use the seals to look at deep water movement, temperature and salinity. Fluorometers on the tags can also estimate chlorophyll content in the water column.
To give you an example – we’ve looked at the association between water masses and foraging success of elephant seals, and used that data to estimate oceanographic currents for changes in the environment. We’ve been able to calculate the rates of sea ice melting and how that’s been affected by the changes in the water column as a consequence of climate change.
How can this information be used for conservation?
Some of the most important things we can figure out is exactly where these animals are travelling to – they’re going to areas where there’s something interesting happening from a biological point of view. One of the things we’ve done is produce habitat models for different species and look into how they’re going to change in the future as the climate changes. (Swoop note: see our interview with Dr Ryan Reisenger on similar research relating to krill.)
If the seals are doing something different, we’re going to be able to detect those changes in the three dimensions, and potentially understand how the oceanography of the area is changing, and what kind of effects are going to cascade all the way up the entire trophic web.
It goes way beyond just the animal – the seals are an incredible source of information for everyone. We haven’t even covered the 1% of everything that we can do with them!
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