Search

This study explores the question of reproductive termination (loss of reproductive ability) in female Japanese macaques (Macaca fuscata) from the Arashiyama West (Texas) troop. We used a large sample of completed lives to identify reproductively terminated female Japanese macaques and to consider reproductive termination in Japanese macaques from a comparative life history perspective, which permits meaningful comparisons to be made with human female menopause. We classified a female as reproductively terminated if the time lag between last parturition and death exceeded two standard deviations of the female's own mean lifetime interbirth interval (Caro et al. [1995] Int. J. Primatol. 16:205-220). Seventy of the 95 females in the sample had at least 3 infants over their lifetime (the minimum required for the calculation of a mean and standard deviation), and thus were included in the analysis. Of these 70 females, 20 showed reproductive termination. Reproductively terminated females ranged in age from 14.5-32.7 years, although in females under age 25, reproductive termination was unlikely. The majority of females up to age 25 showed continued parturition. However, after age 25, reproductive termination was population-wide. Length of postreproductive life for reproductively terminated females varied from 0.07-4.4 years, with a mean of 2.08 years. Variation in length of postreproductive life was not related to the age at death of the female. While the occurrence of population-wide reproductive termination after 25 years does suggest similarities with human female menopause, the age at which this termination occurs is very late in the life span, and it was experienced by only 2.9% of the population. Female Japanese monkeys over age 25 are visibly aged and show outward signs of weakness and deterioration, quite unlike the healthy middle age of menopausal human females. Accordingly, as a life history characteristic, reproductive termination in Japanese macaques does not appear to coincide with menopause as experienced by human females., (Copyright 1999 Wiley-Liss, Inc.)

Theorists argue that mortality in male mammals should be higher than that of females, and many studies of primates followed across the life course have found this to be the case. This study examines mortality patterns in the rapidly expanding Arashiyama West (Texas) population of Japanese macaques (Macaca fuscata) and finds that males have a significantly lower median survival age (12.2 years) in comparison to females (20.5 years). Males and females are born in equal proportions, but by adulthood there are 2-5 females to every male. Males are at higher risk of falling victim to infectious diseases and human-related causes of death, and they are more likely to "disappear" from the population, which is inferred to result largely from emigration. There are no significant sex differences in the risks of dying from predation, non-infectious illnesses, neonatal defect, or social stress. Males become more susceptible to mortality than females once they reach sexual maturity, and they remain at greater risk than females until their old age. There is no evidence that one sex or the other is at greater risk of dying as infants, or as juveniles. Comparing males of different age classes, adolescent and adult males are more likely to die and to disappear than are juvenile males. These findings support the "high-risk, high-gain" hypothesis that males are mainly lost to the population because of their risk-taking behaviors after sexual maturity, rather than the "fragile male" hypothesis that males are more vulnerable to mortality during the period of growth and development.

Lifetime reproductive success, measured by the number of offspring surviving to age five, varied from 0 to 10 in a group of 33 provisioned female Japanese macaques. Of the three contributors to reproductive success, the number of reproductive years, fecundity per year and survivorship of offspring to reproductive age, the first accounted for two-thirds of the variation. Fecundity per year and survivorship were negatively correlated, indicating reproductive costs of reducing interbirth interval. No other demographic measure used, nor the behavioral measure 'dominance rank', significantly correlated with lifetime reproductive success or its components. Age-specific changes in fecundity and infant survival were not found for this sample, neither could cessation of reproduction, even in very old females, be demonstrated.

Thirteen cases of a spontaneous neuropathy were observed among 150 free-ranging Japanese snow monkeys (Macaca fuscata). Necropsy of 4 individuals revealed lesions in the peripheral and central nervous systems. Pathologic changes were associated with ingestion of coyotillo berries (Karwinskia humboldtiana).

The Arashiyama West troop of Macaca fuscata consists of 150 monkeys transported from Kyoto, Japan, in February 1972 to their present location near Laredo, Texas. At this site the animals range over 108 acres and during the study period were only minimally provisioned and disturbed. In the report of a 3-year study of consort partner selection it was suggested that yearlong social bonds within the troop appeared to be distinct from consort bonds formed during mating season. Like Sade, we consider grooming to be a good measure of yearround affinitive bonding in macaques. This study compares the pairs formed for consorting with those formed for yearlong grooming activities, by the 94 individuals who formed consort relationships during the mating season of 1973--1974. It was found that yearlong grooming involved pairs of monkeys which were significantly different from those for consorting. Grooming was relatively frequent between related monkeys, while consort partners were seldom related. In addition, yearlong grooming patterns were not disrupted during mating season. These results suggest that consort and grooming activities are behavioral expressions of two important social networks, involving mutually exclusive social bonds.