Birth seasonality and interbirth intervals in free-ranging formosan macaques,Macaca cyclopis, at Mt. Longevity, Taiwan

Abstract

Thebirth season of Formosan macaqueM. cyclopis during our study started in February and ended in August with a peak in the second half of April and the first half of May. The average birth rate was 82%±21 for 114 females with four years of breeding records. Our study reports that a time span of one year between births can be considered as the norm for the wildM. cyclopis. Of the 288 inter-birth intervals (IBI), 88.5% showed a 1-year interval (mean 364±SD 29 days); 11% showed 2-year interval (727±36 days); and 1% (2 females) had 3-year interval (range 1030–1040 days). The IBI for females that had infant loss within six months of life were the shortest. But there was no significant difference from that of females that had stillbirth (p>0.9) and infant that survived for first six months of life (p>0.06). However, among 255 cases of 1-year IBI, stillbirth or following infant loss within six months of life did significantly shorten IBI for ten days (F 1,253=5.74,p<0.05).