Biology Performance Task: August 2011

Tuesday, August 2, 2011

•The emperor penguin is the largest living species of penguin, standing over three feet tall and weighing approximately 30 kilograms. It can be distinguished from its close relative, the king penguin, by its size as well as its bright yellow upper chest region, which connects with orange-colored ear-patches on the black head. Additionally, the emperor is characterized by a bright orange bill, and the back contains bluish gray hints, while a nice white stomach enables them to blend into their snowy surroundings. Both the male and the female look alike and share similar colorations. The emperor is the best adapted penguin to the cold polar habitat in which it resides.

The courtship of penguins

•Penguins pair off and form monogamous bonds , although some quarrels might take place . This is due to the fact that there is an unequal ratio of males to females ,within some colonies, this could be as extreme as 39.5% male to 60.5% female, often resulting in intense competition for mates. The reproductive cycle involves monogamous pair bonds for each breeding season, usually with a new partner the subsequent year, although there is evidence supporting that 14.6% of pairs are able to recognize one another the following year and re-establish their bond. success off the offspring clearly depends on intensive care and fulfillment of duties from both parents. Different communication signals are important in the duration of the mating cycle. Audible mating songs seem to serve multiple purposes, including identification of gender and identification of the individual. Additionally, sexual behavior is triggered by copulatory poses. The courtship song and bowing behavior are a critical part of pair formation, as well as a parade mutuelle and chant when they mother transfers the egg to the father for. Males will use an ‘ecstatic’ display to attract females, characterized by body positioning and courtship calls. Females will also practice these courtship calls, and calls of both sexes are quite variable and important in partner recognition. These calls are critical for both mate to mate recognition as well as parent to offspring recognition. Calls are important in communicating with fellow group members during feeding and migration, and once the chicks are born, they will rely on these calls to communicate their hunger with their parents. Body positioning is also critical in the penguin community, and the members will often use an appeasement posture to avoid aggressive encounters.

How the emperor penguins reproduce

•Emperor Penguins first begin to breed at approximately five years of age. Emperor penguins travel about 90 km (56 mi) inland to reach the breeding site. The penguins start courtship in March or April, when the temperature can be as low as –40°C. Emperor Penguins are serially monogamous. They have only one mate each year, and stay faithful to that mate. However, the next year, most end up with different mates. Although they attempt to locate the previous year's mate in the next breeding season, most cannot find each other and choose a new mate. In May or June, the female penguin lays one 450 gram (1 lb) egg, but at this point her nutritional reserves are exhausted and she must immediately return to the sea to feed. Very carefully, she transfers the egg to the male, who incubates the egg in his brood pouch for about 65 days consecutively without food by surviving on his fat reserves and spending the majority of the time sleeping to conserve energy. The transfer of the egg can be awkward and difficult, and many couples drop the egg in the process. When this happens, the chick inside is immediately lost as the egg cannot withstand the low temperatures on the icy ground. To survive the cold and winds of up to 200 km/h (120 mph), the males huddle together, taking turns in the middle of the huddle. They have also been observed with their backs to the wind to conserve body heat. If the chick hatches before the mother's return, the father sets the chick on his feet and covers it with his pouch, feeding it a white, milky substance produced by a gland in his oesophagus.

The egg of an emperor penguin

•The gestation period for female emperors is about 63 days. Females will lay only one egg, as it is too energetically expensive to raise more than one offspring. Additionally, only one egg can fit atop the feet, beneath the brood. Once the egg is laid, a risky transfer between the mother’s and father’s feet will occur. This transfer is carefully rehearsed, for if the egg drops and touches the frigid ice, the whole process will be for naught. The transfer of the egg to the male’s brooding pouch will enable the female to leave for the ocean to obtain food and regain strength from this energetically expensive process. The incubation of the egg externally from the female’s body is important to the emperor penguin, because while the female feeds at sea, the father diligently cares for the egg, making male emperors far more devoted fathers than many other species . For nine weeks, as winter intensifies, the fathers of the colony will huddle together for warmth, keeping the eggs safe inside their brooding pouches until the offspring are ready to be born.Male members on the peripheral edges of the group try to ease their way into the warm core of the colony, but this process must be performed with caution, as one false step can cause the egg to fall, become exposed to the -60 degrees Celsius, and the embryo to freeze and die. Thus, huddling behavior within the colony is a critical aspect of emperor penguin survival during these winter months.

The importance of the huddling system

•This huddling can consist of the males gathering together in densely packed groups known as tortues to better withstand to wind (Dargaud, 1993), or the formation of clusters, known as crèches, among the chicks. Within these groups, the penguins will huddle together and continually rotate from the peripheral edge to the inner circle to help endure the cold and wind (Campbell, 2007). On exceptionally cold days, the group will pack closer together, and on warmer days, the colony appears to spread out slightly more . Huddling is a key component of the emperor penguin’s mating system, in that it saves energy during the demanding winter months where they must fast while incubating the egg. It is believed that this behavior allows all members of the group an equal part in energy-conservation, enabling them to successfully incubate their eggs. Both males and females must endure long episodes of fasting, including about 45 days during their courtship plus an additional 65 days for the males during incubation (Gilbert et al., 2006). Thus, huddling behavior is especially necessary to the survival of male emperors, who are forced to live off of fat reserves for months during the courtship and incubation periods. Interestingly, it would appear that lighter penguins tend to form huddles more frequently, perhaps due to the fact that they need to conserve energy more than their heavier conspecifics. The emperors also seem to exhibit huddling behavior away from the colony and closer towards to edge of the ice, thus indicating that huddling behavior may be an instinctive social reaction of a group of penguins and a very valuable means of social thermoregulation.

Food sources and the diving capabilities of the emperor penguins

• Emperor penguins’ primary sources of prey are crustaceans (including krill), small fish, and cephalopods. The amount of each type of prey they choose to consume varies depending on the abundance of prey in a given area due to seasonal changes. Emperors are capable of diving deeper and staying beneath the water for longer durations than any other species of penguin. The record dive duration for an emperor is over 18 minutes and the deepest dive stands at 870 feet .One study reports that, on average, dives last for about three minutes at 65 or 70 feet. it is quite apparent that emperor penguins are nimble beneath the water and exhibit superb diving abilities, often reaching speeds of up to 60 km/h. It is through storing large amounts of oxygen in their tissues that the emperor penguin can remain beneath the water for such long periods of time. The oxygen stores of the emperor have been measured as 3-4 times the amount of typical terrestrial species, thus making them expert divers. Furthermore, penguins are capable of reducing oxygen consumption by reducing heart rates and transfer costs during lengthy dives, enabling them to effectively utilize their underwater habitat and food resources in the harsh Antarctic. the emperor penguin relies heavily on its specialized swimming and diving capabilities to capture prey and survive in the harsh Antarctic.

Predators and other threats against the emperor penguins

• The main threats the emperor faces are giant petrels, as well as occasional attacks from skuas, leopard seals, and killer whales. Chicks are clearly at the greatest risk, due to their small and fragile size, but weakened and starving adults may also be taken as prey. the greatest cause of emperor mortality, however, is freezing potential and the harsh, Antarctic environment. There are some concerns that human disturbances may threaten breeding population numbers, and global warming could potentially impact sea ice and threaten penguin breeding grounds, however this is not an overwhelming concern. The emperor’s relationship to their predators makes them a necessary part of the Antarctic ecosystem. It is believed that colonies are currently stable in numbers, and thus they are not endangered or protected by laws. The emperor penguin requires a static, stable environment where its main enemy is the cold and wind. Any additional disturbances from humans could dramatically disrupt the balance and stability in numbers that they currently have.