Growth in Howler monkeys

Howler monkeys (Alouatta caraya) were studied in northern Argentina and subjected to complete post-mortem examination in connection with field observations of atherosclerosis. In order to estimate age of the animals, data was obtained on gross body dimensions, dental age, and organ weights in 298 animals covering the range of about 1–10 kg. The animals were divided into four size groups, and into male, non-pregnant and pregnant female categories. Statistical parameters were obtained for relative organ weights, organ allometry coefficients, gross body lengths, a body length formula based on the Ponderal Index and dental age. The parameters from howlers were compared with those for rhesus monkeys, chimpanzees, human and general primate organ allometric formulas, and differences due to sex and pregnancy reviewed. It is concluded that the growth pattern in howlers is rather similar to that reported for other primates, which makes it possible to estimate maturity satisfactorily, but that further methods must be developed for post-maturity dating.Publication No. 190 of the Oregon Regional Primate Research Center, Beaverton, Oregon, supported in part by Grants FR 00163 and GM 13605 of the National Institutes of Health.