A major cause of the decline in Onge population is the changes in their food habits brought about by their contact with the outside world. The Onge are one of the least fertile people in the world. About 40% of the married couples are sterile. Onge women rarely become pregnant before the age of 28. Infant and child mortality is in the range of 40%. The Onge's net reproductive index is 0.91. The net reproductive index among the Great Andamanese is 1.40.