Reproductive patterns in pygmy lorises (Nycticebus pygmaeus): Behavioral and physiological correlates of gonadal activity

Abstract

AbstractThe purpose of this study was to evaluate behavioral and physiological parameters of reproduction in a breeding colony of pygmy lorises. To this end, nine male and eight female adult pygmy lorises were kept under natural lighting conditions and monitored through five consecutive breeding seasons. Behavioral data were collected continuously throughout the year on all loris pairs. Behaviors associated with estrogen peaks in females included approaches, leaves, and lunges by females. Whistles were more frequent during estrus, but there was high inter‐individual variability. Males responded to estrous females by persistent following. There was a higher percentage of births in pairs that were together for more than 30 days before onset of estrus, compared with pairs that were put together when females came into estrus. However, these results may have been influenced by factors such as previous familiarity and social compatibility. Fecal testosterone levels were measured using radioimmunoassays and correlated with estrogen peaks and labial swelling of the females. The data showed an annual rhythm in testosterone that was consistent with a July–August mating season. Captive births were significantly higher during January–April than they were during any other months of the year. The earliest testosterone peak in a juvenile male was detected at 58 weeks, while the youngest male to sire offspring was 73 weeks of age at the time of the conception. Zoo Biol 22:15–32, 2003. © 2003 Wiley‐Liss, Inc.