Despite their wild appearance, mother orangutans raise their offspring protectively and affectionately. Observation at Zoo Atlanta in Atlanta, Georgia, shows that a mother orangutan will cradle her baby tightly and give it caresses and kisses. She will also attempt to keep others from looking at her baby by shielding it with her arms and moving away from observers. This nurturing attitude helps to lower orangutan infant mortality rates both in captivity and in the wild.
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Infancy in the Wild
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According to Natural History Notebooks, gestation for a pregnant orangutan lasts from 235 to 270 days, or 8 to 9 months. At birth, a baby orangutan weighs 3 to 4 pounds and begins clinging to its mother almost right away; it will stay attached to its mother's fur for the first four years of its life.
During infancy, a baby orangutan sleeps in its mother's nest and feeds only on its mother's milk. Observations at the Honolulu Zoo show that at about age 4, when the baby is being weaned, the mother shares her food with her child. She shows it which foods are safe to eat and where to find them in season. This is important, as orangutans eat mainly plant material and insects. Eating the wrong thing could cause an orangutan to become ill or die.
Adolescence in the Wild
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The juvenile orangutan learns to construct its own sleeping platforms from branches and leaves, and also to move through the treetops independently. At first, it swings through the trees using only its arms. Later, it learns how to walk on tree branches and jump from place to place. This learning stage lasts until age 7, when the young orangutan will begin finalizing its survival skills until it leaves its mother upon reaching sexual maturity.
The male orangutan reaches sexual maturity at around 10 years old. As an adult, he weighs up to 200 pounds and is 4 to 6 feet tall. Mature male offspring break ties with their mothers completely to seek out the best breeding and feeding grounds. Female orangutans reach sexual maturity at about 12 years old and weigh up to 110 pounds. Females tend to find territories close to their mothers and socialize with them often.
Infancy in Captivity
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Ideally, raising baby orangutans in captivity is the mother's job, just as it is in the wild. According to zookeepers at Zoo Atlanta, it was common practice up through the 1980s for zookeepers to raise baby orangutans from birth. This led to the discovery that orangutans learn how to care for their offspring by being cared for by their mothers. Hand-raised orangutans had no idea how to care for their offspring as adults. Helpless mothers rejected their infants, making hand-raising necessary.
Human Foster Parents
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Today, hand-raising baby orangutans is used only a last resort. If possible, mothers raise their infants as they would in the wild. If a mother orangutan dies or rejects her baby, zookeepers find a surrogate orangutan mother.
During the search for a surrogate, the orphaned orangutan is bottle-fed and sleeps with a human foster parent at the zoo. The infant is also socialized with other orangutans each day under close observation.
Finding a Surrogate
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Ideally, a surrogate mother is chosen from the female orangutans inhabiting the same zoo as the orphaned baby. When the baby is being socialized, zookeepers watch to see which female is most receptive to the infant. That female is chosen as the surrogate and the infant is placed in the chosen female's enclosure.
After finding a surrogate, the new mother and baby are closely observed together to ensure the baby's safety. Once the zookeepers are certain that the mother-child bond is formed, the two are left to act as they would in the wild. The surrogate mother teaches the baby orangutan all it will need to know to thrive.
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