King Penguins Found To Be Extending Their Feeding Grounds
King Penguins (Aptenodytes patagonicus) can be easily confused with their Happy Feet counterparts, the Emperor Penguin (Aptenodytes forsteri), however they are a separate species and can be identified by their height of 70 – 100 cm tall, as well as their brown downy chicks (as opposed to the gray chicks of the 100 m to 122 cm Tall Emperor Penguin). Like most of the natural world, King Penguins are being threatened by global climate change, and have had to adapt to survive.
About King Penguins
King Penguins are the second largest species of penguin, and these birds form large colonies of up to 100,000 breeding pairs. It is estimated that the total population of King Penguins is approximately 2.23 million breeding pairs. King Penguins are found on the subantarctic islands, with the largest colonies found on Crozet Island, as well as the islands of Kerguelen, Prince Edward and South Georgia.
The diet of a King Penguin is 80% fish, and they particularly favor small bioluminescent lanternfish. They are also known to feed on squid and small crustaceans. King Penguin chicks eat the regurgitated seafood fed to them by their parents.
King Penguins are the preferred prey of orcas, leopard seals, fur seals, South American sea lions, and chicks and eggs are eaten by giant petrels and skuas. Unfortunately King Penguins also face some man-made threats. They are experiencing habitat loss in their range due to human habitation encroaching on their nesting areas. Invasive species, such as rabbits, have also devoured the vegetation surrounding their breeding sites, resulting in erosion and landslides. It is also expected that King Penguins will be facing threats from climate change in the future. So, how will the birds react to these impending threats?
Foraging Plasticity in King Penguins
Animals, including King Penguins, are constantly seeking to expand and alter their feeding ranges when possible. Currently this expansion is being driven by climate change as it alters the behavior, habitat, food distribution and abundance of King Penguins. Foraging plasticity is therefore an important survival mechanism in King Penguins to survive environmental changes, as well as life history limitations, such as breeding and molting stages.
Although many of the breeding colonies are doing well and have recovered from human exploitation during the 19th century, it has recently become evident that the largest King Penguin colony on the Crozet Islands has declined by 88% over the past 35 years. A reason for this drastic decline may be due to a southern shift of their main feeding ground, the Antarctic Polar Frontal Zone (APFZ), due to a poleward shift of westerly winds. A southerly shift in feeding grounds may have increased foraging trip duration, reducing breeding success and a reduction in the number of breeding pairs at Crozet Islands. Predictably, there has been an increase in breeding pairs at South George, which is situated southeast of the APFZ, within the altered feeding ground location.
It has also been observed that King Penguins have re-established themselves at historic breeding sites, such as on the Falkland Islands, as well as at Bahía Inútil, Strait of Magellan, Tiera del Fuego, Chile. A new study published in Global Ecology and Conservation aims to look into the new foraging ranges of the Kind Penguins, particularly at the newly established breeding site in Tierra del Fuego, Chile.
The breeding site in Tierra del Fuego differs from other well-established breeding sites, as it is located in a confined environment about 300 km away from the open Atlantic and Pacific Oceans. The penguins at this breeding colony also showed changed foraging behavior from that which has been established as the norm. During the early egg incubation period, foraging trips and dives taken on these trips were much shorter, and dives were much shallower, when compared to penguins breeding on site in the open ocean. It is therefore possible that the birds had to change their traditional foraging strategies to the confined environment with a different quality and quantity of prey in the Strait of Magellan.
The study deployed 32 remote sensing devices on King Penguins from Tierra del Fuego to determine the foraging areas and ranges throughout the year, as well as the characterization of the diving activities and diet during egg incubation and chick rearing periods.
Range Extension and Foraging Behaviour by King Penguins
The study found that the distributional range of Kind Penguins to the Strait of Magellan, Chile, was accompanied by significant changes in their foraging habitats, showing the ability of the species to display plasticity in terms of their foraging behavior. Thirty-one of the birds foraged exclusively within the inshore waters of the Magellan Strait and adjacent channels. The birds did not dive deeper than 160 m in search of food, and relied on a different set of key prey species than the penguins at other breeding colonies. King Penguins are considered off-shore hunters, feeding on fish and squid at depths greater than 150 m.
In order to be successful in the Magellan Strait, King Penguins had to adapt to the confined environment away from the open ocean. Foraging areas were located within 100 km of the breeding site, which resulted in shorter foraging trip durations, and an increase in chick provisioning rates. On average, King Penguins spend about 10 days out at sea when foraging. However, the penguins in the study were observed to be spending on average 4.5 days out foraging. Penguins from Tierra del Fuego thus spend less energy commuting, and are able to feed their chicks more regularly. Despite the increased chick provisioning rates, the particular breeding site at Tierra del Fuego suffers intense terrestrial predation by introduced predators, as well as bacterial and viral diseases not found at other breeding colonies.
Although the exact reason for the re-establishment of the breeding colony in Chile is not known yet, it is exceptional to find that a top predator has been able to adjust its usual foraging strategies to a different environment, and also established a new breeding site. The results of this study suggest that King Penguins can potentially forage without depending on the APFZ, and may be able to survive predicted climate change impacts better than anticipated.