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Factors Affecting Party Size in Chimpanzees of the Mahale Mountains

Factors Affecting Party Size in Chimpanzees of the Mahale Mountains We studied factors affecting party size and composition of wild chimpanzees at Mahale (M group) over an 11-month period. Parties with 1–5 individuals were most frequent (37.8%; 153/405 parties); they included 94.7% of all male parties (n = 76) and 81.3% of all female parties (n = 75). The median of monthly values was the standard for analysis. We divided the year into four periods based on the median size of monthly bisexual parties (30.9 individuals; includes both males and females): monthly bisexual party sizes were larger in May–June (period II) and October–January (period IV) and smaller in February–April (period I) and July–September (period III). Only bisexual parties changed in size with period. The number of fruit items (=species) eaten was fewer in periods II and IV when abundance per item appeared to be great. The sizes of bisexual parties, which included cycling females with maximal anogenital swelling, were larger, and their representation (%) in all bisexual parties was greater in periods III and IV. The numbers of both cycling females and cycling females with maximal anogenital swelling were also larger in periods III and IV. The percentage of cycling females with maximal anogenital swelling was greater in periods II and III. The results of this study and those of Nishida (1979) suggest that seasonal variation in party size of Mahale chimpanzees maintains a relatively consistent annual cycle. The factors assumed to affect party sizes are fruit availability and the presence of cycling females with maximal anogenital swelling. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png International Journal of Primatology Springer Journals

Factors Affecting Party Size in Chimpanzees of the Mahale Mountains

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References (40)

Publisher
Springer Journals
Copyright
Copyright © 1998 by Plenum Publishing Corporation
Subject
Life Sciences; Evolutionary Biology; Zoology; Animal Genetics and Genomics; Anthropology; Animal Ecology; Human Genetics
ISSN
0164-0291
eISSN
1573-8604
DOI
10.1023/A:1020322203166
Publisher site
See Article on Publisher Site

Abstract

We studied factors affecting party size and composition of wild chimpanzees at Mahale (M group) over an 11-month period. Parties with 1–5 individuals were most frequent (37.8%; 153/405 parties); they included 94.7% of all male parties (n = 76) and 81.3% of all female parties (n = 75). The median of monthly values was the standard for analysis. We divided the year into four periods based on the median size of monthly bisexual parties (30.9 individuals; includes both males and females): monthly bisexual party sizes were larger in May–June (period II) and October–January (period IV) and smaller in February–April (period I) and July–September (period III). Only bisexual parties changed in size with period. The number of fruit items (=species) eaten was fewer in periods II and IV when abundance per item appeared to be great. The sizes of bisexual parties, which included cycling females with maximal anogenital swelling, were larger, and their representation (%) in all bisexual parties was greater in periods III and IV. The numbers of both cycling females and cycling females with maximal anogenital swelling were also larger in periods III and IV. The percentage of cycling females with maximal anogenital swelling was greater in periods II and III. The results of this study and those of Nishida (1979) suggest that seasonal variation in party size of Mahale chimpanzees maintains a relatively consistent annual cycle. The factors assumed to affect party sizes are fruit availability and the presence of cycling females with maximal anogenital swelling.

Journal

International Journal of PrimatologySpringer Journals

Published: Sep 29, 2004

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