KEY POINTS:
He is used to marching across the frozen expanse of Antarctica, his sleek silhouette and monochrome plumage marking him out from the harsh, windswept landscape.
Plunging hundreds of metres into the dark, icy depths of the Southern Ocean and spending weeks on end expertly hunting fish is just a way of life for him. But waddling along on an adapted treadmill inside a rickety Perspex box, Roy the king penguin looks far from majestic.
Although he might not have appreciated it at the time, he and his friends were recruited as scientific researchers in an ambitious project to gauge the effects of overfishing and global warming on the Southern Ocean ecosystem.
Scientists have suspected for a long time that warming seas and intensive fishing in the waters around Antarctica are affecting marine stocks.
They believe that if left unchecked, that could have serious implications for penguins and many other species in the food chain, from microscopic plankton to killer whales.
Measuring fish stocks using traditional methods is a costly and inexact science. Researchers spend huge sums chartering or hitching rides on fishing boats to make the long and perilous journey deep into the ice of the Antarctic, where scientists and volunteers trawl the few patches of ocean they have the time and money to reach, simply counting what they find.
"The Southern Ocean is so vast that it's very difficult and expensive to sample with any validity using boats and fishing nets," says Dr Lewis Halsey, who is leading the penguin project with a team from Birmingham University's School of Biosciences. "So why not recruit a natural-born swimmer with good local knowledge to do the job?"
King penguins inhabit the subantarctic islands on the northern reaches of the Southern Ocean, where, during the winter, they breed. Then, in the summer, they embark on a lengthy diving expedition to find food for themselves and their chicks.
This double life makes them ideal research recruits. Halsey says: "You can get to them easily on land, equip them cheaply with a data-logging chip, and off they go into the ocean, leading us to the fish.
"King penguins are large and numerous, so they have a significant role in the ecosystem - effects felt by them will be felt by everything else."
Using penguins might save Halsey a lot of effort and improve his data, but reaching his recruits is a hard task. The Birmingham team travels thousands of kilometres from the Midlands to the tiny Indian Ocean island of Reunion, before taking a week-long voyage to the Crozet archipelago, a French territory of islands about halfway between Madagascar and Antarctica.
The islands are home to huge colonies of penguins, seals and albatrosses, and a permanently manned research station where Halsey lives for up to five months at a time. "It's an amazing place," says Halsey, "and while it's very rugged and can be very windy, it's not like being Captain Scott - there isn't always snow and it can even get quite warm in the summer.
"It's also a perfect place to gain access to penguins and work with them in a controlled environment."
But just how do you train a penguin to count fish? Halsey's experiments are based on the theory that by measuring the energy king penguins spend hunting for their favourite food, the lanternfish, you can calculate how many of them there are - the harder penguins have to work to find food, the fewer fish there are likely to be.
To measure energy expenditure, Halsey implants smart-tags into the abdomens of 50 birds.
These tags measure the temperature at the back of the bird's throat, recording a temporary drop when it swallows a cold fish. This means scientists can work out when, and roughly how much, the penguins eat.
The data logger includes a hydrostatic sensor that measures pressure, which increases as the birds dive. If lanternfish are scarce, the penguins are forced to go as deep as 350m.
Finally, and crucially, the chip monitors the bird's pulse, which ranges from a sedentary 30 beats a minute while it sits on land, to a rib-rocking 200 beats a minute as it powers through the water hunting its prey.
But heart rate alone is not a reliable enough indicator of energy expenditure. A more accurate indication is how much oxygen the birds use while hunting, something that's impossible to measure in the wild. Cue the treadmill. Halsey and his team plonked a bemused Roy on a specially adapted running machine.
Researchers also built a channel 30m long in which a penguin would swim against water flows of various strengths. By placing a sealed Perspex box around Roy as he swam or ran, Halsey could measure how quickly the penguin consumed oxygen. At the same time he recorded Roy's heart rate.
The treadmill and water flow were then varied to find out how the heart rates changed at different levels of exertion.
By comparing this data with the heart-rate information retrieved from the penguins when they return to the same spot of dry land, Halsey can estimate energy expenditure, and, in turn, the number of fish in the sea.
Halsey and his team presented their preliminary findings at a meeting in Glasgow of the Society for Experimental Biology.
The findings show that king penguins have entered a vicious cycle of working harder to find less food.
That suggests that overfishing and the warming of the Southern Ocean is pushing lanternfish deeper and further south, upsetting the ecological balance of the whole ocean.
For Roy and his fellow kings, it means working harder to find lanternfish or, increasingly, relying on squid.
"You can't get as much energy from squid as you can from fatty, oily lanternfish," Halsey says.
"This means they have to eat more to make up the calories, which requires even more energy and takes more biomass out of the ocean, and that has knock-on effects on other species that rely on squid."
Roy hardly looks enthused by his impromptu workout, and many would say surgically implanting probes into wild animals is a cruel intervention.
But Halsey says the penguins are willing participants in his experiments. "They don't like being handled at first," he says, "but because they don't have predators on land, they're pretty placid animals.
"Once they're on the treadmill and know they won't be harmed, they orientate themselves and just get on with walking."
This compliant demeanour during the winter, combined with an ability to cover thousands of kilometres while feeding in the summer, means king penguins receive a lot of attention from students of the Southern Ocean.
Last year, a team of Australian scientists used 15 penguins, as well as eight elephant seals, as "oceanographic observers".
Researchers stuck temperature and pressure sensors to the animals' heads, which, using GPS and radio transmitters, helped build a 3D profile of sea temperatures.
Roy was Halsey's favourite hunter. "He was such a placid animal," Halsey says. "When we would have problems with the treadmill, we would put the penguins into a holding pen while we fixed it.
"But with Roy I would just put him next to me on the ground and he would stand happily waiting, almost as if it was me and him sorting the equipment out together."
Halsey insists that implanting the chip is just as painless. "We insert it under anaesthetic and stitch the penguin up with the type of thread used by plastic surgeons.
"Then we get them back into the colony where they wake up away from humans."
And without this kind of research, Halsey says the implication for Roy's colony and habitat could be drastic.
"If fishing and the warming of the seas goes on at this rate, it could result in reduced breeding success, which would be a tragedy.
"It's difficult to get across how phenomenal these creatures are. They waddle round on the beach in the colony and see and feel the same things we do - the rain, the hail, the cold.
"Then for weeks at a time they disappear and lead this mysterious life chasing down fast-moving prey at incredible depths in almost total darkness.
"Then they come back a little fatter but otherwise as if nothing has happened."
- Independent
