According to Science Daily, researchers have noted a drastic drop in population size in the biggest colony of king penguins, located in the National Reserve of the French Southern and Atlantic Lands (TAAF). Researchers were able to detect the 88 percent population drop in the colony, specifically located on Ile aux Cochons, in the Iles Crozet archipelago, by using high-resolution satellite images.
Researchers say the reason may be environmental, but noted that the exact causes of the king penguin colony collapse and why the population drop was as large as was discovered remain a mystery.
According to the article, the king penguin, with the scientific name Aptenodytes patagonicus, has been known since the 1960s on Ile aux Cochons, located in the southern Indian Ocean. The colony had the distinction of being known as the world’s largest king penguin colony and the second largest of all penguins. Scientists last visited the island in 1982, noting 500,000 breeding pairs and over 2 million penguins in the colony. Researchers were since unable to take new estimates of the colony’s population due to both isolation and inaccessibility.
After calculating the area the colony of king penguins occupied at different periods between 1960 and the present, researchers discovered the drastic population drop, noting that the king penguin colony’s territory has yielded to encroaching vegetation.
A major climatic event related to El Nino in the late 1990s coincides with what data shows to be the start of the king penguin colony population decline. The event, says Science Daily, “temporarily affected the foraging capacities of another colony 100 km from Ile aux Cochons, causing it to dwindle. The same process may be responsible for the fate of the Ile aux Cochons colony.”
The size of the colony at any given time may be subject to what the article refers to as “density-dependent” effects. In other words, competition between individuals increases as the population grows, thereby lowing the growth of the members of the king penguin colony. Repercussions such as lack of food would therefore be amplified, triggering an “unprecedented rapid and drastic drop in numbers, especially following a climatic event like the one at the end of the 1990s.”
Researchers are also entertaining disease as a possible cause for the king penguin population’s staggering decline as a hypothesis, although none of the theories currently being considered by the research team can account for the sheer magnitude of the king penguin population decline on the island.