Biology Reference
In-Depth Information
Table 6.2.
Demography: Age and sex make-up of population at Padangtegal
Year
Adult
males
Adult
females
Immatures
Infants born during
major birth peak
(May-August)
Observed deaths
(June-August only)
1986*
5
26
38
2 (11 total infants
nursing)
1990*
8
29
60
3 (15 total infants
nursing)
1991*
11
35
76
7 (19 total infants
nursing)
1992*
11
42
80
3 (19 total infants
nursing )
1998
14
43
65
7
1
1999
11
48
66
16
2
2000
10
55
74
15
3 (2 inf, one ad M7)
2001
10
60
91**
19
3 (3 inf)
2002
21
80
103
23
5 (3 inf, one ad male,
one ad female)
* 1986-1992 data from Wheatley
1999
** includes 12 older subadult males
Table 6.2
includes the newborn, “black infants,” and nursing “brown” infants
for the period 1986, 1990-1992 as these are how the data were reported by
Wheatley (
1999
). The
Table 6.2
entries for this study (1998-2002) contain
only those infants born during the May-August period as we have observed
that some individuals nurse for more than one year and pelage changes can
vary somewhat between individuals. From 1998-2002 we observed two birth/
mating peaks annually (May-August and December-January), with a small
number of births occurring outside of these peaks. Sixteen neonates were born
during May-August of 2000, nineteen in 2001, and 23 during the same period
in 2002 (
Table 6.2
). Females are observed copulating almost immediately after
giving birth, suggesting a post-partum false estrus period. Interbirth intervals
ranged between 16-36 months. A majority of the adult females in the popu-
lation gave birth to infants during the 1998-2002 period, with some giving
birth to as many as three offspring. One female successfully gave birth to a set
of twins that have survived past the age of two years. Wheatley
et al
. (
1996
)
reported an extremely high infant mortality rate (~90 percent) in 1990 at this
site, however our observations suggest that the current rate averages less than
30 percent for the period 1998-2002.
Between 1998 and 2000 at least ten adolescent males disappeared from the
site. We assume that they attempted emigration as neither our team nor the
