One question I’m asked a lot about my job is: how do you “vet” a one-tonne elephant seal? Well firstly, it makes the 300kg seals seem really titchy and easy. But why, you ask? Why have I travelled to Antarctica to immobilise elephant seals that can weigh from 250kg up to 1,000kg and more? My immediate answer is: who wouldn’t do that if they had the chance, so I guess that’s a bit telling.

I’m in awe of the extremes of the Antarctic and I love being a vet, but that’s not all. The work itself is part of cutting-edge climate science as well as a chance for us to understand how one of the ocean’s top predators interacts with its environment.

The project I’ve been working on, labelled “Seals as Oceanographers”, is part of Australia’s monitoring of the Southern Ocean through its Integrated Marine Observing System, supported by an Australian Antarctic Science Grant from the Australian Antarctic Division. It involves attaching tracking devices to the tops of elephant seal heads. These trackers provide information on seal movement, and the structure of the ocean itself.

Esther Tarszisz checks the heart of an elephant seal. Photograph: Ross Nimmo

The Southern Ocean helps drive global-scale circulation, and up until seals pitched in, there was hardly any data, especially below the 60 degree South mark or in winter, where conventional sampling methods are near impossible. The trackers, in addition to telling us where the seals go and how deep they dive, collect information on ocean salinity, ocean temperature and depth. This allows researchers to understand how and where water masses form, something vital to understanding global heat and oxygen mixing rates. This project is part of an international collaboration at many sub-Antarctic and Antarctic sites.

When it comes to sedating these huge beautiful predators in order to attach the tracking device, Dr Clive McMahon, expert seal biologist, and his research assistant catch the seal using a canvas head bag. Then I, as the Davis team veterinarian, step in and inject the seal with a drug agent (incidentally exactly the same one I use in my “real-world” job as a small animal veterinarian to sedate cats for grooming – but at a fraction of the dosage).

The injection is given intravenously into the extra-dural vein, which is a vein running within the vertebral column and is one of several cool anatomical adaptations of elephant seals that enable them make their incredibly deep and long dives (down to 2km!). This involves sitting at the tail end of a not-particularly-pleased-about-it-seal and getting the injection in first go.

The first time I tried this was possibly one of the most stressful veterinary moments in my career – second only to the first time I was asked a question as an actual vet, no longer a student. While I am never blasé about it, I’m confident that I’ll get the vein quickly and efficiently. This usually calms the seal down in about 30-60 seconds and lets us get on with our work.

We weigh the seal, measure it (both girth and length) and glue the transmitter to the fur. All this time I’ve been monitoring the anaesthetic, just like with a patient at home, and making sure he’s alright (all the seals at Davis station are males. The females don’t tend to come as far south).

‘I think the tagged seals look infinitely more handsome.’ Photograph: Martin Biuw/AFP/Getty Images

The whole procedure takes about 40 minutes and the patients show no evidence of distress afterwards. The drugs have a component that causes amnesia, and they often shuffle back for a snooze with their mates afterwards or head out for a lazy swim along the shore. Even better, some go straight off and start collecting data – the machine turns on as soon as they’re in the water and stays on until they moult. Dr McMahon conducted a study that conclusively demonstrated no difference between growth and behaviour of tagged versus non-tagged seals. Except I think the tagged seals look infinitely more handsome, but then I always have been a fan of body-art.

All the data is freely available to the global community, in real-time from the Integrated Marine Observing System’s web portal, as well as a number of open source journal articles, for those who are of an inclination to read scientific journals.

Of all the work I’ve done in the name of veterinary science – learning how to dart megafauna in South Africa (for research like fitting them with tracking collars), volunteering on carnivore projects in Botswana (leopards and lions), Zambia (African wild dogs) and Belize (jaguars) as well as conducting field work for my PhD following orangutans through the jungles of Borneo – this has been the most rewarding project I’ve been involved with. It’s such far-reaching science that incorporates excellent research on biology, ecology and climate science.

Working on the Seals as Oceanographers project is a privilege and a joy – although, sometimes my fingers don’t feel the same. I can’t do anything dexterous, like give injections, with clumsy warm gloves, and it’s something you feel (or not feel) in sub-zero temperatures. And Antarctica – there’s really no place like it. I go to work surrounded by ellie seals, penguins and icebergs. I’m the luckiest vet in the world.