por He Emperor penguin (Aptenodytes forsteri) is a southern aquatic bird representative of the Sphenicidae family and the Spheniscihormes order. The Sphenicidae family includes all extant penguin species, which are widely distributed in the southern hemisphere.
The species was described by Gray in 1844 and dedicated to the German naturalist Johann R. Forster, who actively participated in the voyages of Captain James Cook navigating exhaustively around the world in the discovery of the so-called «Terra Australis incognita”.
The genus refers to the inability of the species to fly and that it is capable of immersing itself in water. Emperor penguins have been a source of admiration and fascination since the first expeditions to Antarctica.
They are the birds that are distributed and live further south, in ecosystems practically unaltered by human activities. However, due to the increasing influence of global climate change, the survival of the species may be compromised in the coming decades.
A. forsteri It is a bird with congregatory habits in the reproductive season. A total of 53 reproductive colonies and an estimate of mature adults of approximately 595,000 individuals are currently known. Despite these estimates, population trends for the species have not been assessed recently.
These penguins take advantage of the resources available near the fast ice shelves. The diet contemplates extraordinary variations according to seasonality and the population density of the prey.
Emperor penguins are diving predators. In general, they can have dives whose duration varies significantly depending on the success of capturing food or if they are only exploratory dives. Foraging time also varies with seasonality and day length.
Its immersion capacity is quite changeable. They generally dive to depths less than 100 meters, however, they have been recorded at depths of 200 meters and a maximum of almost 500 meters.
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Characteristics of the Emperor Penguin
Emperor penguins are characterized by being the largest and with the greatest body mass of the current penguin species.
Males are usually slightly more robust than females, weighing up to 40 kilograms, while females can weigh up to 30 kg. Both sexes can reach heights of up to 1.20 meters.
Coloration is similar in both sexes. The plumage is characteristically black on the back, head, chin, back, dorsal part of the fins, and tail. They have a broad white to yellowish cream spot on the neck that fades to white towards the front.
In addition, they present the auricular region of an intense yellow color. These yellow spots are almost separated by a deep black band that extends over the shoulders. The belly is white like the ventral surface of the fins.
The chicks have a coloration similar to the adult. The body is covered by silvery gray feathers with white patches surrounding the eyes and cheeks, the dorsal region of the head is black and they do not have the yellow lateral spots on the head but are white.
Diving adaptations
These penguins have solid bones to prevent damage during deep dives. In addition to this, they have physiological adaptations similar to those of some mammals that occupy the same habitat.
The hemoglobin of these penguins has a high affinity for oxygen, making it very effective in transporting small amounts to the tissues during deep dives.
On the other hand, they are capable of lowering metabolic rates during breeding periods, in order to withstand the long winter. During which, the males do not feed and incubate their eggs.
Habitat and distribution
Emperor penguins live in the southern hemisphere. They mainly occupy the polar regions of Antarctica, in an elevation range from sea level to 500 meters above the coastal fast ice caps.
They are concentrated in oceanic marine habitats, intertidal zones, and neritic habitats, as well as terrestrial when they congregate for reproductive activities.
These penguins settle on the fast ice that surrounds the coastal zone of Antarctica. Generally their breeding areas are established in areas protected from strong winds either by walls of solid ice or icebergs.
taxonomy
There are two representative species of the genus Aptenodytes. Aptenodytes patagonicus It is a species very similar to the emperor penguin, however, its size and body mass is considerably smaller. In addition, they differ widely in their behavior, breeding periods, and other ecological aspects.
Recently, some phylogenetic works indicate the existence of a common ancestor between penguins and albatrosses that lived in a period between 62 and 73 million years ago. The gender Aptenodytes diverged about 40 million years ago.
There is evidence of a third species of Aptenodytes in the fossil record, being known as a.ridgeni and who lived at the end of the Pliocene, in New Zealand. So far there are no known subspecies within the emperor penguins.
State of conservation
Until 2012, the species had been cataloged by the International Union for the Conservation of Threatened Species in the category of «Least Concern (LC)».
However, as of that year it was considered an «almost threatened» species, as a significantly rapid population decline has been evidenced and is expected in the next three generations, given projections of imminent climate change.
It is estimated that at least three quarters of spawning populations are vulnerable to predicted changes in sea ice conditions and one fifth of these may be irreversibly gone by the year 2100.
The probable decrease in the extent, thickness and concentration of sea ice, as a result of the persistence of the wind and other variables such as temperature and precipitation, are the most worrying factors.
The disappearance of a colony with 150 breeding pairs on Emperor Island has already been documented. This local disappearance was attributed to the decrease in the seasonal duration of sea ice, particularly stable ice that is suitable for nesting.
other threats
Other currently evidenced disturbances are the establishment of scientific bases for the investigation of the colonies of these penguins and the tourism developed near some of them. Although the percentage of colonies subjected to these pressures is very low.
On the other hand, the development of commercial krill fishing and the collection of silver fish (Pleuragramma antarcticus) in Antarctic waters poses a great risk if the nutritional needs of those animals that take advantage of these resources are not considered.
Oil spills also pose a wide danger in populations located near the area of exploitation.
Reproduction
This species breeds almost exclusively on fast ice near the Antarctic coast and even on the coast itself, sometimes as far as 200 kilometers from the open sea.
Emperor penguins have an annual breeding cycle and it is one of the most striking within this group of birds.
Initially, the colonies begin to establish themselves at the end of March and the beginning of April, when the extreme Antarctic winter begins and contrasts with the reproduction period of the other penguin species (spring or summer).
Courtship and mate selection
Once they are at the nesting sites, a complex phase of finding a mate begins. Because there are a greater number of females, they must compete for the company of the males.
The males emit a series of characteristic calls and of an individualized nature, whose objective is to attract the attention of a female in the case of being single or to attract a couple obtained during the previous reproductive season.
Emperor penguins can establish monogamous reproductive relationships, however, this occurs in 15% of cases due to various ecological factors.
Once a bond is established, the male emits a series of movements that are observed and imitated by the female. The male then moves through the colony, usually closely followed by the female. To initiate mating, the male bows his head to the ground and is immediately imitated by the female or vice versa.
Laying and breeding
Emperor penguin females only lay one egg which is comparatively smaller relative to other smaller seabirds. Oviposition occurs between May and June.
These birds do not build a nest, a fact that is in contrast to the rest of the penguin species. Once the egg is laid, the female’s energy reserves decrease significantly.
Because of this, the females leave the egg in the care of the males to incubate it and undertake a return trip to the coast to feed for about two months.
The transfer of the egg is usually complicated and many of them are lost in the process, because they fall on the ice that is at temperatures as low as -40 °C. The male has a fold or incubation bag covered by feathers on its lower ventral region.
The approximately 500 gr egg rests in perfect balance on the upper region of its legs. The incubation process lasts approximately two months, while the females are absent, which is the longest incubation period among birds.
Care during growth
The eggs begin to hatch in late July and early August. Up to this point, the male has lost more than 50% of his weight. Initially, the chicks are fed by a substance produced in the esophagus of males with a high lipid and protein content.
Once the females return, they replace the males that leave to feed and regain weight. About a month later, they return to the colonies and take turns with the females to carry out breeding and feeding activities in an exchange cycle that can occur more than 5 times.
After the young reach a suitable size to be left alone, groups or nurseries of the same are established. While both parents feed in the ocean.
At the beginning of November, the hatchlings begin to moult their juvenile feathers as a starting point and preparation to adopt an independent life at sea during the summer season in late December and January.
In this period, the availability of food is usually high and a large part of the Antarctic fast ice is thawed, a fact that increases the probability of survival of the pups that manage to reach this stage.
Nutrition
Emperor penguins descend to a suitable depth evaluating the availability of food….