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Vol. 40 No. 1, 2001
Troop Size and Structure in Free-ranging Formosan Macaques (Macaca cyclopis) at Mt. Longevity, Taiwan
Minna J. Hsu1,* and Jin-Fu Lin2
1Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan 804
2Shi-Pu Junior High School, Kaohsiung County, Taiwan 840
Minna J. Hsu and Jin-Fu Lin (2001)
Among the 19 extant species of the genus Macaca that are found in
southern and eastern Asia as well as northwestern Africa, the Formosan
macaque is one of the least known. A long-term field study to
investigate the population dynamics and social behavior of 7- 16 troops
of free-ranging Formosan macaques at Mt. Longevity, Taiwan has been
conducted since July 1993. Between Dec. 1994 and Dec. 1997, a
systematic census was conducted on a biweekly basis to record data on
the demography of Formosan macaques. We used focal animal sampling and
ad libitum sampling twice per week in respective troops to record data
on social behavior including male replacement and fission processes.
The maximum density of macaques has been estimated as 26 individuals
per km2 in Oct. 1997. The average troop size was 26.1 ± 9.7 (n = 7) in Jan. 1995 and it reached the highest level of 47.0 ± 21.2 (n
= 13) in Aug. 1997. Two cases of fission were observed. The branch
troops, la and Aa, that were formed as a result of fission had the
smallest size with 9 individuals in the beginning, while troop l had
the largest size of 86 individuals. Births were recorded mainly between
Apr. and June (97%) with a peak in mid-Apr. to mid-May. The
annual average overall sex ratio was 1.06 ± 0.28, while the adult sex
ratio (adult males to adult females) was 0.53 ± 0.12. The average
tenure length of alpha males was 16.8 ± 18.9 mo (n
= 34) and ranged from 1 wk to a maximum of 6 yr. The average alpha male
tenure in newly formed troops was significantly shorter (p
< 0.01) than that in the remaining troops. About 88% of alpha male
changes occurred between Oct. and Feb., which paralleled the peak and
the end of the mating season, respectively.
Key words: Reproduction, Troop composition, Sex ratio, Male tenure, Fission.
*Correspondence: Tel: 886-7-5252000 ext. 3623. Fax: 886-7-5253623. E-mail: hsumin@mail.nsysu.edu.tw
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