REPRODUCTIVE STRATEGIES AND THE INFLUENCE OF DATE OF BIRTH ON GROWTH AND SEXUAL DEVELOPMENT OF AN ASEASONALLY-BREEDING UNGULATE - REEVES MUNTJAC (MUNTIACUS-REEVESI)
Ng. Chapman et al., REPRODUCTIVE STRATEGIES AND THE INFLUENCE OF DATE OF BIRTH ON GROWTH AND SEXUAL DEVELOPMENT OF AN ASEASONALLY-BREEDING UNGULATE - REEVES MUNTJAC (MUNTIACUS-REEVESI), Journal of zoology, 241, 1997, pp. 551-570
Unlike most species of deer, Reeves' muntjac does not have a seasonal
reproductive cycle. Births are equally distributed throughout the year
and, irrespective of season of birth, females start breeding when the
y have reached a minimum body weight of about 10 kg. A significantly s
maller proportion of females is born in the autumn/winter than the spr
ing/summer, but there is no effect of maternal age or condition on foe
tal sex ratios for first or subsequent pregnancies. Whilst aseasonal b
reeding increases female productivity, males are only able to hold ter
ritories encompassing the ranges of a number of does for a relatively
short period of time. It is argued that for muntjac theres much less i
nter-sexual variation in lifetime reproductive success than for season
ally-breeding polygynous cervids. Hence, although muntjac are sexually
dimorphic and polygynous, females do not invest preferentially in mal
e off spring. Young males can be fertile from 36 weeks of age,when the
ir first antlers are still in velvet. Whilst season of birth has no ef
fect on the rate of sexual development in females, it does for males,
with autumn-born male fawns attaining sexual maturity earliest. This a
ccelerated development occurs in the period following independence fro
m the mother, and there is no evidence of a maternal cost in producing
male fawns. Since the canine tusks are the main weapons for intra-sex
ual conflict, there could be clear gains in terms of reproductive succ
ess for males that attain sexual maturity, adult weight and adult tusk
size quickly, even though their first antlers are much smaller than t
hose of older bucks. The hypothesis is presented that, for muntjac, th
e majority of a male's lifetime reproductive success is achieved relat
ively early in life when the canine tusks are in pristine condition, a
nd that bucks lose their territories, and associated access to oestrou
s does, once the canines are broken.