Hidden lives of penguins

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Penguins are hardly secretive – in addition to their loud bray, they are poorly camouflaged on land, and stumble around haphazardly with their clumsy waddling gait.

Publicly accessible breeding colonies allow visitors to watch the birds raise their young from egg to fledgling. Many fawn over the fluffy adolescents and tour guides offer facts about how parents take turns to incubate and fish for their offspring. However, once the adults have reared their chicks, they leave the colony and nobody knows where they go or what they do.

A nesting penguin at the Boulders colony. Photo: René de Klerk

Studying penguins outside of the breeding season is difficult and expensive. Breeding birds are central-place foragers, meaning they return regularly to the same point after each trip, in this case their hungry chicks. Collecting data is fairly easy during this period.

Non-breeding birds spend the majority of their time at sea, making them harder to observe. Until recently, technology to power tracking devices for long periods was unavailable.

The non-breeding season is important in the life cycle of penguins as they are termed catastrophic moulters – replacing all their feathers at once. Because they rely on their feathers for waterproofing and insulation, they have to remain out of the water while they grow a new set.

Penguins undergo a three to four week fast each year during this period. In preparation, some birds come close to doubling their body weight before coming ashore. At the other end of the cycle, the newly feathered hungry birds need to find food quickly to replenish those resources lost during the fast.

 

Fitting a tracking device. Photo: Andrew de Blocq.

BirdLife South Africa began a long-term project looking into these pre- and post-moult phases in 2012 in partnership with the FitzPatrick Institute of African Ornithology. They have tracked birds from Dassen Island 55km north of Cape Town, Bird Island in Algoa Bay and Stony Point Nature Reserve in Betty’s Bay to see where the birds go during these important periods.

The study uses solar-powered GPS trackers, allowing scientists to remotely monitor the progress of
the birds. The results have been surprising. While penguins from Bird Island continue with the central-place foraging strategy and rely on areas near the island, birds from Dassen Island and Stony Point behave differently. Pre-moult birds from Dassen Island adopt one of three strategies. The least common strategy is to remain nearby.

Penguins tend to venture northwards or eastwards to find food, and the proportion of birds adopting each strategy seems to be changing over time. In the early years of the project, most birds chose to head north, some getting as far as halfway to Namibia.

This area was historically rich in fish like sardine and anchovy, but climate change and fishing pressure has led to stocks shifting towards the Agulhas Bank in the southeast, turning these previously bountiful areas into blue deserts.

Birds heading north risk taking longer to fatten up before moulting, or have to head back to moult at
a sub-optimal body condition. More birds from both Dassen Island and Stony Point head southeast, rounding Cape Agulhas and spending four to six weeks off De Hoop Nature Reserve and Stilbaai before returning westwards to moult.

Photo: Andrew de Blocq

This is a return journey of more than 1 000 kilometres and has revolutionised the way scientists think about the spatial protection of penguins.

Conserving penguin breeding sites is a priority, but protecting areas far removed from colonies has emerged as a key strategy in fighting the decline of this iconic species.

The project is sponsored by the Charl van der Merwe Trust.

Written by Andrew de Blocq, coastal seabird conservation project officer at BirdLife South Africa

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