A study of a black howling monkey ( Alouatta caraya ) population in northern Argentina

A population of Alouatta caraya in northern Argentina had an ecological density of 130 animals per km 2 . Mean troop size varied from 7.2 to 8.9 individuals, and the ratio of adult males to adult females from 0.58 to 0.51. Infants comprised from 6% to 14% of the population, juveniles from 16% to 21%. These percentages probably vary seasonally in response to a birth peak at the beginning of the dry season. Males were age‐graded in multi‐male troops. Sexual dimorphism was extreme in this species. Males were all black and averaged 6.7 kg; females were yellow‐brown and averaged 4.4 kg. Juvenile males retained the pelage color of the female until approximately 4.5 yr of age and 5 kg in weight. No genital mimicry or exaggeration occurred in this species. Vocalizations of A. caraya were similar to those of A. seniculus , both of which tend to be lower pitched than those of A. palliata .