The British Antarctic Survey (BAS) has recently noted that a small colony of well documented emperor penguins no longer reside on their island off the West Antarctic Peninsula. Scientists believe that the loss of the colony is due to a reduction in sea ice, which would normally be an important habitat for the penguins to nest and forage for food. This report comes from the February edition of the scientific journal.
According to researchers from BAS and the Scott Polar Research Institute, this is the first documented case of an emperor penguin colony disappearing.
All penguins have a common trait in their ability to fly, but emperor penguins stand above the rest; literally. They are the largest of all the penguins, reaching heights of nearly 4 feet (1.2 meters) tall and weighing 70 to 90 pounds (30 to 40 kilograms). Emperors can mate as early as 4 years of age and live to be 20 years old.
Aside from being the largest, these penguins are arguably one of the most biologically interesting. Emperors do not migrate outside of Antarctica, but actually breed on the sea ice in some of the coldest conditions on Earth. Instead of building nests or defending a fixed territory, they use their warm bodies to incubate and raise their young. Emperors are the only Antarctic bird that breeds in winter, and this unique breeding habit may have developed to allow chicks to grow to be independent at a time when food is most plentiful and predators are few.
The small colony of these penguins, previously residing on Emperor Island, was discovered in 1948 when a team of scientists recorded seeing 150 pairs gathering to breed. Unfortunately these numbers have been declining steadily since 1970. As of 2009, a high resolution survey taken from the sky recorded no remaining trace of the once thriving colony. The observed decline and loss of this colony has an uncanny correlation with a rise in local air temperature and seasonal changes in the duration of the sea ice.
Regarding the first documented loss of an emperor penguin colony, the lead author from BAS, Dr. Phil Trathan, writes,
“It is not clear whether the colony died out or relocated. Emperor penguins are thought to return each year to the sites where they hatched, but the colonies must sometimes relocate because of changes in the sea ice. It is clear that emperor penguins are vulnerable to changes in sea ice and the one site in Antarctica where we have seen really big changes in ice is the West Antarctic Peninsula. For much of the 20th century, this region has warmed at an unprecedented rate, particularly in recent decades. Continued climate change is likely to impact on future breeding success.”
The paper also looks into alternative hypothesis of why this colony disappeared. Possibilities include unusual weather conditions, impacts from tourism, disease, and loss of food due to competition with fisheries. According to the authors, competition with fisheries and impacts from tourism can be ruled out, and there is no data to support the hypothesis of disease or unusual weather conditions.
A prolonged warm period in the late 1970’s resulted in an emperor penguin population decline of nearly 50% in the Terre Adélie region. This warm period caused a reduction in sea-ice coverage and is blamed to be the reason for the increased adult mortality, particularly among males. The species is unfortunately considered to be highly sensitive to climate changes. Studies show that even an abnormal increase in sea-ice coverage can also lead to reduced rates of egg hatching success.
Due to the effects of climate change and industrial fisheries, the emperor penguin is on the decline and is up for consideration to be placed on the US Endangered Species list.
photo credit: www.usap.gov