Rockhoppers struggle to adapt but are beset in how they divide duties when rearing chicks
- Rockhopper penguins use a strict division of labour when raising chicks
- The males stand guard over the chicks for up to four weeks after hatching
- While they fast the females go out to sea to catch food to feed the chick
- In lean months, however, the couples can struggle to get enough food
For most parents, bringing up a child requires them to work together as a team to overcome the challenges that inevitably come their way.
But for one diminutive family of penguins, their style of parenting is increasingly being put at risk by climate change-induced food shortages.
Researchers have found rockhopper penguins have been unable to adapt their habits to cope with years when food supply is in short supply.
Eastern rockhopper penguins (pictured) have a strict division of labour when it comes to rearing chicks, but this could be putting their species at risk as climate change causes food shortages. In lean years, males spend more time away trying to put on weight after a long fast, meaning chicks get fed less
This means in these lean years, the ability of the chicks to survive is greatly reduced and experts fear it may threaten the long term survival of these species.
The problem, they have found, is the fixed regime used by crested penguins, including rockhoppers, to care for their chicks.
TOASTY HUG OF PENGUIN HUDDLES
They endure some of the coldest temperatures on the planet as they nest through the Antarctic winter.
But emperor penguins get so warm as they huddle together on the ice that they have to resort to eating snow to cool down.
Researchers have found some of the birds get so hot in the tight bundle of bodies they risk overheating.
They also discovered huddles are more complicated and temporary than previously thought - lasting on average 50 minutes at a time.
Previous estimates suggested the penguins hunkered down for as long as the storms lasted, which could be hours.
The birds were thought to stay warm by rotating from the outside to the inside of the huddle.
But scientists at the University of Strasbourg in France have found the huddles regulate the birds' temperatures in a more complicated way, with some members breaking free to cool down.
All penguin parents take it in turns to care for their offspring and fend off predatory seabirds while the other goes off to sea to feed and bring back food for the chick.
But while most avoid long periods of fasting by alternating guard duty and foraging regularly, the seven species of Eudyptes penguins do not.
Instead males guard and fast for the first three to four weeks after the eggs have hatched while the females go off to sea to look for food.
During the following six weeks, chicks gather together in creches and are fed by both parents who make extended multi-day trips to sea.
In a study published in the journal Behavioral Ecology and Sociobiology, biologists have shown the pattern of these parental roles never vary even if environmental conditions and food conditions do.
Kyle Morrison, a biologist at Massey University in New Zealand, and Dr David Thompson, from the National Institute of Water and Astmospheric Research in Wellington, said: 'We have shown that the unique division of labour of a Eudeyptes penguin appears to constrain reproductive investment and chick growth during nutritional stress.
'Eudyptes penguins, ostensibly anchored in a reproductive strategy maladapted to a marine environment where food availability is less predictable, will continue to be highly threatened from climate change.'
The researchers studied Eastern Rockhopper Penguins - Eudyptes chrysocome filholi - on New Zealand's sub-Antarctic Campbell Island over two consecutive breeding seasons.
Female penguins spend the first three to four months catching food and providing for the chicks (pictured) while the males stand guard against threats from predators and other penguins
Large seabirds like brown skuas (pictured) can predate chicks, meaning adults must stand on constant guard over their offspring. Males fast for up to four months to protect their chicks, meaning they spend more time at sea during lean months trying to regain weight when their guard duty ends
During the 2011 season, abundant food was available, but the following year was lean.
The researchers measured how often chicks were fed, their growth rates and how often adult birds returned to feed their chicks.
They found fewer chicks were successfully reared during the lean months of 2012 than the previous year.
Males in particular also spent more time at sea in search of food as they desperately sought to regain the mass they lost during their chick-guarding fast.
This mean the males were less likely to regularly bring food to their offspring and meant that chicks were fed less often.
Researchers warn the strict division of labour among rockhopper penguins (pictured) and other crested penguins means they will struggle to rear chicks as food shortages become more common in the future
Male Eastern rock hopper penguins, which breed in rocky colonies below towering cliffs on Campbell Island, New Zealand (pictured), can spend up to four weeks on dry land fasting as they stand guard over their chicks, meaning they lose weight. After this time they take turns with the females to go out to sea to feed.
The study found these chicks subsequently grew more slowly, making them less able to survive the challenges that lay ahead.
Mr Morrison, who conducted the research as part of his PhD, and his colleagues warned that climate change is expected to make the situation worse in the future.
They said that as the climate changes, lean years are likely to become more common.
If the penguins were to take a more equal share of guarding duties, up to 34 per cent more feeds could be provided to the chicks as they are reared.
However, it appears the penguins have adapted to their current parenting strategy as the females are smaller and less aggressive, making them less effective at guarding chicks.
The researchers said: 'Both sexes made longer foraging trips and provisioned less often under nutritional stress, but males decreased their investment in chick-provisioning more than females by making extra-long self-feeding trips early in the crèche period.
'The canalized division of labour strategy of Eudyptes penguins is maladapted to more frequent years of nutritional stress under climate change.'
THE WOBBLY MARCH OF THE PENGUINS
Their comical waddle is a popular attraction at zoos around the world and has helped to cement penguins as stars of the screen in films such as March of the Penguins and Happy Feet.
But their strange gait appears to also bring a key advantage to the sea birds when they find themselves trekking across the land - by allowing them to pick up speed.
Researchers trained eight king penguins to walk on a treadmill to allow them to conduct one of the first detailed studies of the animals' waddle - and they filmed the hilarious results.
The researchers found that as the creatures walked faster, their side-to-side motion also increased.
This, the scientists found, allows the penguins to take longer and wider strides, which is crucial to helping them pick up speed.