Semen samples were collected from adult fertile bonnet monkeys twice a mont
h by penile electroejaculation for twelve consecutive months. Various param
eters like semen volume, weight of ejaculate and coagulum, sperm count, spe
rm motility, sperm morphology, and functional parameters e.g. plasma membra
ne integrity, in vitro nuclear chromatin decondensation and acrosomal statu
s were evaluated to assess within and between animal variations. Effects of
seasonality, if any, on quantity and quality of semen were also studied. C
onsiderable intra- and inter-individual variations in the geometric mean va
lues were observed for semen volume, weights of ejaculate and coagulum, and
sperm counts during the study period. On the other hand, sperm motility, m
orphology, and functional parameters showed less within and between animal
variations. Results on motility, morphology, and functional parameters indi
cated that good semen quality was maintained throughout the year. Various r
outine and functional parameters did not show any annual variations. The di
urnal rhythmicity in circulatory testosterone levels was observed throughou
t the year. The study shows lack of seasonality in exocrine and endocrine t
esticular functions and further suggests that motility, morphology, and fun
ctional parameters are better indicators of semen quality in captive bonnet
monkeys.