Observations of mating, birthing and parental behaviour in three subspecies of slender loris (Loris tardigradus and Loris lydekkerianus ) in India and Sri Lanka.

Studies of the life history parameters of slender lorises in captivity have led to conflicting results regarding gestation length, birth seasonality, interspecies variation in litter size and the degree of parental care given to offspring. During the course of field studies of Loris lydekkerianus lydekkerianus, L. l. nordicus and L. tardigradus tardigradus, data were collected on these life history variables, as well as on behaviours relating to mating. All 3 taxa displayed courtship behaviour involving the pursuit of a female by multiple males. Mating corresponded closely with captive observations, with a period of prolonged single intromissions lasting 3-11 min. One gestation period of 163 days was calculated for L. l. lydekkerianus. Births for all 3 taxa were distributed throughout the year, and males were seen mating throughout the year. All 3 taxa gave birth to singletons and twins; no subspecific pattern in litter size was evident. Females carried infants for the first 4 weeks of life and were regularly attended by males, which groomed both the mother and her offspring. After infants had been parked, female L. l. lydekkerianus and L. l. nordicus rarely returned before dawn, though males visited and played with infants. Female L. t. tardigradus maintained proximity with their infants, whilst males were not observed in proximity to infants during the night. All 3 taxa slept in social groups. High-energy milk, in combination with male care, may aid in the potentially high reproductive output of 4 infants per year.