How many offspring does a mother have?
Once they have reached an age of approximately 10 years, female mountain gorillas give birth to one baby every 4 years. 26% of the babies die in their first year. If the mother transfers between groups while she has a baby or if another silverback male takes over the group, the baby is frequently killed by the new male. However, to date this has been observed only in the mountain gorillas of the Virunga Volcanoes.
As most gorilla mothers have only a few offspring who survive to adulthood, gorilla numbers increase only very slowly. One mountain gorilla mother holds the record with six surviving offspring. Another female gave birth to eight babies, but only two of them reached sexual maturity. The fertility of free ranging mountain gorilla females has not been observed to decrease with old age.