The biology of prolonged lactation in wild Macaca sinica: Interbirth intervals, maternal depletion, infant mortality

A sample of 442 female toque macaques distributed among 39 independent
social groups were briefly captured, sedated, and released (within one
day) during 13 different years in the period 1986-2002 at the natural
forest site of Polonnaruwa, Sri Lanka, where long-term sociobiological
research has been conducted (1968 to 2023).  All macaques were
individually identified and had known life-histories.  Lactation
was determined by testing females for the presence of absence of milk by
manually massaging the mammary tissue.  Female reproduction in
this wild population was depicted from different perspectives. 
Firstly, lactation and weaning were linked to offspring age, as well as to
female reproductive status (cycling, gestation, and quiescence). 
A second data set examines interbirth intervals in relation to lactation
duration, diet, and somatic growth or parity. Differences in diet quality
were also related to menarche.  A third data set examined female
body condition (using skinfold thickness as a measure of % body fat) to
diet quality and differences in the expenditure of foraging time between
lactating and non-lactating females. A fourth data set considered the
relation between infant mortality during peak lactation and the depletion
of female metabolic energy balance as indexed by early weaning (cessation
of lactation) and a shift to female reproductive quiescence.  In
the publication some of these data  were integrated with
mother-infant behavioral relationships as cited from an independent study
of the same population. A final data set indicates the names of
participants who contributed to both the long-term demographic records,
milk collections and estimates human effort for different phases of this
research.