Slow lorises breed every 12 to 18 months, at a time of year when seasonal food levels are rising to a maximum. Females may come into estrus at any time of year. When in estrus they make frequent high-pitched whistles to attract a mate. After a gestation period of 191 days, females give birth to one or two offspring. Birth often occurs in the animals’ nest, but may occasionally take place in the open. Infants are always parked or left in the nest while the mother forages. Newborn infants have grey bodies and silvery-white hands with long glistening fur that disappears at 11 weeks. If accosted, slow loris babies can produce ultrasounds to alert their parents. It has been hypothesized that adult slow lorises can produce a toxic saliva, and they will lick their young to protect them from predators. At 11 weeks, infants’ coats darken to their adult colors. The offspring are weaned at six months of age, and reach sexual maturity between 17 and 21 months.