RESULTS
Male replacement, pregnant
females, unweaned infants and their fortunes
We observed 18 male replacement events involving 16 OMUs and 15 adult
males between January 2006 and March 2020 (Case #1 - #18,Table S1 ). Two events
occurred when no females were pregnant or caring for unweaned offspring
(#7 and #18). Eight pregnant females were present during male
replacement events, four of which were attacked by new males, which
subsequently resulted in two abortions (#1 and #3), one gave birth but
the newborn was killed by the new male (#11), and one returned to stay
with ousted male and gave birth and weaned her offspring (#17). All
other pregnant females were not attacked by the new males and gave birth
to their offspring.
Thirty-one unweaned infants were present following male replacements.
Two of them and their mothers left the unit with the ousted male and
survived. Although half of all remaining unweaned infants (15/29) were
attacked by new males, only three
infants (#2, #8 and #11) were
killed by the first set of attack, and one more infant was killed after
repeated attacks (#8). Therefore, except of four infanticides, most
unweaned infants (27/31) present during male replacements are known to
have survived throughout the
mating season either because their mothers stayed with the ousted male,
transferred to another social unit after an unsuccessful attack, or were
tolerated by the new male (Fig 1 and Table S1) .
The difference in mortality of fetus and infants during male
replacement compared to stable periods
Two abortions were observed during a total of 117 pregnancies outside of
male takeover events. Therefore, there is a significant increase of
abortions following male replacement (Fig 2 , 2/8 vs 2/117,
Z-Score = 3.6212, p < 0.001). Twenty-three unweaned
infant deaths were observed during a total of 121 births, with two
infants who were present during times of male replacement dying for
unknown reasons in winter (potentially because of low temperature and
disease). We compared the difference of death rates between the infants
and the fetus + infants present during times of male replacement and
those present at other times. There is no significant difference of
death rates between the infants present during times of male replacement
and those present stable periods
(6/31
vs 17/90, Z-Score = 0.3408, p > 0.05), and between
the fetus + infants present during times of male replacement and those
present stable periods (8/33 vs 19/92, Z-Score = 0.7102, p> 0.05).