Timing of births in sympatric brown howler monkeys (Alouatta fusca clamitans) and northern muriquis (Brachyteles arachnoides hypoxanthus)

We monitored the birth patterns of sympatric brown howler monkeys (Alouatta fusca clamitans) and northern muriquis (Brachyteles arachnoides hypoxanthus) during a 4‐yr period from October 1996 to August 2000 at the Estação Biológica de Caratinga, Minas Gerais, Brazil. Brown howler monkey births (n = 34) occurred throughout the year, and birth frequencies did not differ between rainy and dry season months. The aseasonal birth patterns of the howler monkeys differed significantly from the dry season concentration and dry month peak in muriqui births (n = 23). We found no effects of infant sex or the number of females on interbirth intervals (IBIs) in our 10 howler monkey study troops. IBIs of brown howler monkeys averaged 21.2 ± 2.5 mo (n = 8, median = 21.0 mo), and were significantly shorter following dry season births than rainy season births. Their IBIs and yearling survivorship (74%) were similar to those reported for other species of howler monkeys, but yearling survivorship was much lower than that of muriquis (94%), whose IBIs were more than 12 mo longer than those of the howler monkeys. Our study extends comparative knowledge of birth patterns in Alouatta to a poorly known species, and provides insights into the different ways in which diet and life history may affect the timing of births in large‐bodied platyrrhines under the same seasonal ecological conditions. Am. J. Primatol. 55:87–100, 2001. © 2001 Wiley‐Liss, Inc.

[1]  M. D. Di Bitetti,et al.  When will the stork arrive? Patterns of birth seasonality in neotropical primates , 2000, American journal of primatology.

[2]  K. Strier,et al.  Seasonal and Social Correlates of Fecal Testosterone and Cortisol Levels in Wild Male Muriquis (Brachyteles arachnoides) , 1999, Hormones and Behavior.

[3]  K. Strier,et al.  Behavioral and endocrine characteristics of the reproductive cycle in wild muriqui monkeys, Brachyteles arachnoides , 1997, American journal of primatology.

[4]  K. Strier Reproductive Ecology of Female Muriquis (Brachyteles arachnoides) , 1996 .

[5]  L. Fedigan,et al.  Interbirth interval variation in three sympatric species of neotropical monkey , 1995, American journal of primatology.

[6]  K. Strier,et al.  Habitat, density and group size of primates in a Brazilian tropical forest. , 1993, Folia primatologica; international journal of primatology.

[7]  K. Strier Faces in the Forest: The Endangered Muriqui Monkeys of Brazil , 1992 .

[8]  K. Strier Atelinae adaptations: behavioral strategies and ecological constraints. , 1992, American journal of physical anthropology.

[9]  K. Strier Diet in one group of woolly spider monkeys, or muriquis (Brachyteles arachnoides) , 1991, American journal of primatology.

[10]  D. Rumiz Alouatta caraya: Population density and demography in Northern Argentina , 1990, American journal of primatology.

[11]  R. Rudran,et al.  Red howler monkey birth data I: Seasonal variation , 1987, American journal of primatology.

[12]  R. Rudran,et al.  Red howler monkey birth data II: Interannual, habitat, and sex comparisons , 1987, American journal of primatology.

[13]  D. Lindburg Seasonality of reproduction in primates. , 1986 .

[14]  K. Glander,et al.  Female reproductive success in a group of free-ranging howling monkeys (Alouatta palliata) in Costa Rica , 1984 .

[15]  R. Sekulic,et al.  Gestation length red howler monkeys , 1982, American journal of primatology.

[16]  K. Glander Reproduction and population growth in free-ranging mantled howling monkeys. , 1980, American journal of physical anthropology.