Scientists already knew that orangutans typically nurse their offspring for six or seven years. However, new research, published in May 2017 in the journal Science Advances, extends the timeline of that nursing behavior for at least another year. Evidence from the barium levels in apes’ molars indicates that orangutan mothers continue to supplement a young orangutan’s solid food diet for many years. Most primates typically supply milk for a set period of time, then decrease milk production when the youngster moves on to solid food. The new dental analysis, however, shows that after infancy, the barium levels spiked about once a year, presumably during seasons when fruits and insects were less plentiful.
Keeping young orangutans fed:
- “We’ve found the first evidence for a seasonal pattern of increasing and decreasing milk consumption over several years,” says lead study author Tanya Smith.
- The researchers analyzed orangutan molars from four young Bornean and Sumatran orangutans, looking for biochemical signs of breastfeeding -- specifically signs of barium from breast milk.
- Because orangutans are so reclusive, biologists have great difficulty trying to observe them nursing their babies. Orangutan mothers find private, hard-to-see spots in trees and typically nurse their young at night.