A Growing Family
Mark was a happy, playful baby, probably very much like wild siamang babies in Sumatra. Under the watchful eye of her mother, she climbed all around the zoo enclosure, but always returned to Suzy after a few minutes for reassurance. Like all little apes, Mark seemed to need a lot of physical contact with her mother--hugging, patting, nursing, grooming. Zoo officials felt very relieved that the siamangs’ family life was so normal. They knew too well the psychological problems young apes can develop when they are rejected by their mothers.
By the time Mark was three months old, she had begun to sample adult siamang food--apples, oranges, bananas, onions, sweet potatoes, lettuce, bread, and sunflower seeds. In the wild, small gibbon species like white-handed gibbons eat more fruit than leaves. Siamangs eat more leaves and greenery. But in the zoo, siamangs and white-handed gibbons receive essentially identical diets, and both species seem to thrive. Some zoo siamangs like greens such as lettuce best, while others prefer fruits they would never see in their native habitat, such as oranges or apples. Each ape has its own favorite foods. Little Mark liked bananas.
Of course, bananas were not yet an important part of her diet. She was still an infant and, although she was developing perhaps three times as fast as a human infant, her main source of nourishment remained her mother’s milk. Gradually, over a period of months, Mark began to eat more adult food. By the time she was a year old she was not dependent on Suzy’s milk. She would continue to nurse for comfort as long as Suzy would allow it, probably until the next baby was born. But for all practical purposes, Mark was weaned.
Throughout Mark’s infancy, the siamang family was left alone. The animals were not handled by the zookeepers. Except for feeding the gibbons and cleaning their enclosure, humans did not enter the family’s territory. Everyone wanted conditions at the zoo to be as close as possible to conditions in the jungle. The benefits of this policy were apparent: Unk and Suzy and their daughter behaved very much like wild gibbons.
When Mark was just about one year old, Unk and Suzy mated again. On March 20, 1964, their second baby was born. Again the siamangs were model parents, and zoo officials saw no reason to interfere with the family. The adult animals had been successful in raising Mark; they could certainly handle a second child. Everyone looked forward to watching the two young siamangs growing up together.
Eighteen days later the new baby died. The zookeepers realized the baby was dead before Suzy did. She clutched it tightly, struggling to hold it when the keepers took it away. A post mortem examination revealed that the baby had died of pneumonia, a very common cause of death among apes.
Even in the wild, pneumonia probably kills many newborn gibbons. Tiny, hairless babies are very susceptible to chills as their mothers swing through damp treetops. A high rate of infant mortality keeps the siamang population from growing too large for the available territory,