ECOLOGY, NUTRITION, AND TIMING OF REPRODUCTIVE EVENTS IN AN ASIAN PRIMATE, THE HANUMAN LANGUR (PRESBYTIS-ENTELLUS)

Ecological conditions, feeding and ranging behaviour as well as physic al condition of female Hanuman langurs (Presbytis entellus) were studi ed in order to analyse the major influences on the timing of reproduct ive events. The langurs inhabited a semi-evergreen forest dominated by Sal trees (Shorea robusta). The climate was dominated by the summer m onsoon lasting from May to September. Availability of plant phytophase s was markedly seasonal, with fruiting as well as hushing of the six m ain food plants during the monsoon. Feeding and ranging behaviour of t he females varied with food availability and its distribution. High di etary quality was only obtained during a short period from May to July . Physical condition of the females varied in accordance with dietary quality and energy expenditure, with a good physical condition during the second half of the year. Births occurred from January until June, with most births around the energetically worst period of the year. Th e results indicate that, in contrast to several other non-human primat es, most females of this population gave birth too early to meet the o ptimum lactation requirements. Complete weaning mainly took place duri ng an energetically bad time of the year (October to December). Howeve r, it can be inferred that the reduction of suckling bouts prior to th e next conception took place when high quality food was available. Con ceptions were confined to the months of July to November, coinciding w ith the time of best physical condition. Moreover, females who conceiv ed were in a better physical condition than those who failed to concei ve, suggesting a primary influence of nutrition on the probability of conception. Seasonality and timing of births may be the result of a re gular seasonal shortfall of resources influencing the ability of the f emales to ovulate and to conceive.