Troop history,female reproductive strategies and timing of male change in Hanuman langurs,Presbytis entellus |
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Authors: | P Winkler |
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Institution: | 1. Institute of Anthropology, University of G?ttingen, Bürgerstr. 50, 3400, G?ttingen, FRG
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Abstract: | Female reproductive data are presented from 9 years of longitudinal observations on two troops of Hanuman langurs (Presbytis entellus) living around Jodhpur, India. On the basis of 89 live births interbirth intervals were calculated to examine the effect
of demographic factors on reproductive behaviour and troop composition. Sex of an infant seems to influence the length of
intervals which are longer after the birth of female infants at an average of 1.7 months. It is suggested that this may be
an outcome of differential maternal investment by allocating more time and energy towards female infants who run a higher
mortality risk than male infants, at least up to an age of 27 months. Troopspecific interbirth intervals are influenced by
social events. If the last infant is still alive when the next one is conceived, the intervals are significantly longer than
after the premature loss of an infant (Bijolai troop: 15.6 vs. 12.1 months; Kailana-1 troop: 16.7 vs. 11.4 months). During
undisturbed male tenureship intervals are shorter than after a male change (Bijolai troop: 14.3 vs. 16.0 months; Kailana-I
troop: 15.6 vs. 17.5 months). Thus the frequency of male changes can influence the demography of a troop. Furthermore, the
data suggest that take-overs are optimally timed by males. New males tend to take over a troop when most of the females are
cycling. |
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Keywords: | Presbytis entellus interbirth intervals maternal investment timing of male change |
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