A new wave of elephant seals becomes animal oceanographers

On Kerguelen Island in the inhospitable southern Indian Ocean close to Antarctica, elephant seals are fitted with sophisticated data collection devices to gather vital ocean information only they can obtain that helps scientists predict climate change and the future of our oceans, and study and protect the seals themselves. 

Around 60 elephant seals are fitted with the data collection devices when they return to a tiny French territory in what is known by NASA as the “‘Desolation Islands”, in January and February every year to moult. The devices, which weigh roughly 0.1% of the elephant seals’ body mass are attached painlessly to their new hair by members of the Animal-Borne Ocean Sensors (AniBOS) network team. AniBOS uniquely integrates oceanography with biology and has been a Global Ocean Observing System (GOOS) network since it began in 2020.

In late 2021, the ‘Animal-Borne Ocean Sensors’ AniBOS project was endorsed by the UN Decade of Ocean Science for Sustainable Development. 

The relationship between AniBOS and GOOS is unique because the network delivers across all three of GOOS’s critical themes: climate, ocean health and forecasts / early warnings. Data gathered by AniBOS also enables us to understand how animals respond to a dynamic, changing ocean and provides a foundation for integrating that data with existing and new and emerging GOOS networks.

Apart from the elephant seals, AniBOS works with other marine animals. These are mainly Wedell seals and turtles but AniBOS is exploring the possibility of fitting devices to sharks and seabirds. The type of data collected depends on the species and the animal’s life history characteristics. Some species may be coastal and only traverse the upper 100 metres of the ocean, which averages 4000 metres deep. 

Elephant seals are different.

As Dr. Clive McMahon of the AniBOS network, who has studied elephant seals his entire career, explains, “Elephant seals dive up to 2000 meters around 80 times a day and have the fantastic ability to dive under Antarctic sea ice and access areas like coastal shelves that other platforms are unable to easily reach. They’re also searching for food in areas where the ocean processes we need to study are happening.”

They may look cute but they’re doing vital work for us.

Fitting the devices

Wherever you’re travelling to and from the Antarctic or sub-Antarctic , you have to get through “some fairly hellish waters,” as McMahon describes them. “It’s always a great relief for me to get off the ship.”

Weather conditions on the island can be tough. In winter, it’s obviously extremely cold but in summer it can actually be warm enough for t-shirts and shorts. As the island is in the middle of the legendary Roaring Forties, famous for their ferocity, the winds are always blowing and the waves are toweringly high.

When the three person expeditions arrive on the island to fit devices, members receive first aid and remote field training before setting off on an eight-hour trek to the field and the hut where they’ll live for weeks on end. They go out and look for seals every day.

Capturing the seals and fitting the device is not as a dramatic process as one may think. “For someone like me who’s been around these animals for 30-odd years, it’s like seeing old friends again. You know everything about them,” McMahon says.

The team looks for seals that weigh between 300 and 600 kg. These aren’t the largest, for two reasons. Capturing the very biggest seals can be dangerous but, more importantly, it’s the smaller seals that travel to the Antarctic coast and send back the best data on what’s happening with dense water formation and Antarctic bottom water formation. This is where the densest water in the ocean forms and the current around the Antarctic starts, driven by the extremely cold and windy conditions just off the Antarctic continent. 

The first step in the process of fitting a seal with a device begins with eyeballing it to estimate its mass so that the correct dose of anaesthetic is given to send the seals to sleep for between 30 and 40 minutes. Anaesthetic is either administered into the muscle or intravenously into a large vein in the lumbar region while the seal has a cone-shaped bag over its head. The latter is the more challenging of the methods but also the most effective as the animal is asleep in around 30 seconds.

In general, as McMahon says, “It’s a calm, easy affair, which is how we like it.”

Once they’re out in the field, the three person team will live, work and eat together in a fairly confined space so it’s important to select the right people. AniBOS looks for calm, careful and accommodating people who work well with large animals. People who have previously worked on farms before going to university are often ideal because they have the practical experience of working with large animals and understand them.

Although the only connection to the outside world is by radio and – apart from the odd treat and a glass of wine or two at Christmas, as McMahon puts it, “It’s a simple, happy life. In the evenings, people sit around, play cards, read or tell stories that get taller every night.”

Gathering vital data

Data is collected using sophisticated electronic sensors that cost approximately €7000 each and produce long-term data streams on key marine environmental variables, hydrography, animal behaviour and ecology. 

The seals collect roughly three profiles per device three times a day. Compared to an Argo float that provides one profile every ten days, this is an enormous amount of data. 

As Dr. McMahon says, “A device is usually attached to an elephant seal for eight to nine months before it falls off or is removed when the seal returns to Kerguelen Island to moult again. We recover around 30 instruments every year and are able to download the complete record of the seal’s movements for around 290 days at a 4-second resolution. This adds up to an enormous amount of information on the physics of the ocean and the behaviour of the animal.”

The data collected complements observations of temperature and salinity within the upper ocean in areas such as high latitude, shallow coastal shelves that have historically been under-sampled because of the presence of sea ice, limited satellite coverage and logistical costs. Observations of temperature and salinity in the hard to reach parts of the upper ocean are urgently needed to support our understanding of climate and ocean variability.

Increased observations from areas elephant seals navigate with ease greatly improves our ability to observe the structure of the ocean and the animals that live in it. This is especially important because the southern Indian Ocean is one of the areas that is changing rapidly and is considered the globally dominant region for heat and CO2 exchange.

Alongside the vital work elephant seals are doing to help us understand climate change, they are also offering us the opportunity to gather valuable data on biology such as genetic composition, ecosystem structure and function, species populations and individual traits.

Data collected is sent back via the Argos satellite constellation to organisations such as the Sea Mammal Research Unit at St. Andrews University in Scotland where it is decoded and shared with AniBOS. It is then made freely available to the broader science and forecasting community where it is used in areas such as weather forecasting.

Minimising negative effects on animal welfare and adhering to best animal handling practices is a vital part of AniBOS’s work. An AniBOS Ethical Advisory Board oversees every aspect of the elephant seals being fitted with devices.

‘We’re very confident what we’re doing will not harm the seal,’ says Dr. McMahon.

AniBOS and the future of ocean science and observing

As a global, inclusive network AniBOS is committed to building relationships with new communities of experts and institutions that broaden knowledge of currently under-sampled ocean regions. 

Looking to the future, AniBOS observations will be further integrated with other existing and new or emerging GOOS networks as well as the Committee on Earth Observation Satellites (CEOS) satellite ocean virtual constellations.

As Fabien Roquet, Co-Chair of AniBOS alongside Dr. Clive McMahon, says, “Our focus is on providing the kind of data and information oceanographers want most.”

Roquet, who heads up the physical oceanography side of things has been involved with seal tagging since 2004 when he was first a junior engineer. Now a Professor at the University of Gothenburg, he’s the leading data specialist for AniBOS.

“Our technological challenge is to fit the most powerful, smallest and lightest instruments on animals and we have to make tradeoffs between quality and quantity and getting the data,” Roquet says. 

“That’s why, from the very beginning, the focus has been and still is largely on elephant seals. They’re large, easy to catch and go far and deep. But we are looking at other animals.”

AniBOS is exploring the potential of devices attached to turtles in the Indian ocean and Indonesian region, in particular. Although turtles such as the leatherback dive as deep as 300 metres, the data collected from turtles is focused on surface and near-surface properties of the ocean. “Local weather responds very much to the characteristics of the mixed layer,” Roquet explains. “It’s where the ocean comes into contact with the atmosphere and is an important barometer, especially when you want to predict tropical cyclone development,” explains Roquet. 

The data-gathering potential of sharks and seabirds is also being explored but here AniBOS faces different challenges. It’s more difficult to work with sharks as they don’t surface predictably and regularly and they have to be captured at sea and fitted with devices. Despite the fact that the whole endeavour of fitting devices on animals started with seabirds back in the 1990s, they are small and constrained in energy so it’s not possible to place large, sophisticated data-gathering devices on them. But they are increasingly being used to gather information about the ocean and environmental conditions. 

As Emma Heslop, Programme Specialist for GOOS says, “There’s no question that the large number of potential animal platforms for observing and the relatively low cost of instrumentation mean that AniBOS can make an even more significant contribution to GOOS. Among other things, this includes gathering information vital to enabling us to benefit from and sustainably manage the ocean.”

But, for now, it’s elephant seals that are the attention-grabbing heroes of the AniBOS story. 

“Remember the photo of the two elephant seals wearing devices that went viral in 2016” asks Dr. Clive McMahon. “It became a meme because it was funny but it also did a great job of raising AniBOS’s profile. There’s a lot of curiosity around what we’re doing and that gives us real potential to engage and educate young people.

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