Observations of parturition among captive patas monkeys (Erythrocebus patas)

Six cases of labor and delivery by laboratory-housed patas monkeys (Erythrocebus patas) are described. Five of the births occurred during the daytime, and the sixth occurred just after the usual “lights out” time. Although it was impossible to determine the actual onset of labor, the final 1.5–0.5 hr before parturition were observed in all cases. Throughout labor, females tended to begin a contraction every 2–4 min and contractions usually lasted 35–60 sec. Females did not show common patterns of change in contraction frequency or duration as birth neared. It was not possible to describe patas monkey labor and delivery in terms of “stages.” Postpartum, females typically began cleaning their infants within 90 sec and picked them up within 5 min. Placental delivery times varied among females, as did the extent of placental consumption. One “mother-only” - reared female proved to be an inadequate mother.     

Patterns of mating among male patas monkeys (Erythrocebus patas) in Kenya

An habituated group of wild patas monkeys was observed in Kenya for 550 h in 1984. Observations were made primarily during an interval that, as previous studies at the same site had demonstrated, coincided with the annual mating and conception periods. Earlier field studies of patas at other sites had reported that heterosexual patas groups had only a single resident adult male and that mating was harem-polygynous. At the Kenya site, by contrast, as many as six males were simultaneously resident and mated in the group during the conception period. Males adopted a variety of tactics to gain access to receptive females, ranging from opportunistic mating to attempts at sequestration that resembled consort behavior in other cercopithecoids such as savanna baboons and rhesus macaques. Aggressive competition for access to females took place among the males, although the number of completed copulations per male did not bear a positive relation to agonistic dominance rank. For patas monkeys, harem polygyny is only one available option within an overall mating system that is best described as a form of promiscuous polygyny, especially during periods when conception is most likely.     

Color changes in the haircoat of patas monkeys (Erythrocebus patas)

Caged patas monkeys were evaluated monthly to determine changes in the color of their hair during infancy, adolescence, pregnancy and lactation. From birth until 3 months of age the facial and anterior crown hairs were short, sparse, and completely black. The body fur was a fine, short, fawn-colored hair mixed with longer black hairs which produced a black-tipped effect. During the second 3 months of life the body fur and anterior crown fur became coarser, longer, and changed to a red-brown color. The facial hairs thickened and became longer, but remained totally black. A thin line of black hairs outlined the brow and temple. The black chin hairs were gradually replaced by white from 7 to 24 months of age, and the upper lip hairs changed from black to white during the second year of life. Color changes related to pregnancy and lactation were confined to the nosepatch, cheek, and browline hair. The nosepatch and cheek hair changed from black or grey to completely white, and the browline faded to the approximate color of the body fur. These changes began approximately at the end of the second trimester of pregnancy, maximized during the third month of lactation, began to darken 1 to 2 months later, and returned completely to the black, nonpregnant colors approximately 1 year postpartum. In one nonlactating female, the darkening was delayed until 500 days postpartum and in one female ovariectomized in the light color phase, the darkening was complete 200 days later. The cause of these changes is believed to be hormonal, resulting from altered endocrine function during maturation and pregnancy, which may alter melanocyte stimulating hormone activity.     

Naturally occurring Yersinia enterocolitica septicemia in patas monkeys (Erythrocebus patas)

Two cases of Yersinia enterocolitica septicemia occurred in a breeding group of 22 adult patas monkeys (Erythrocebus patas). Affected animals had acute clinical signs of depression, weakness, dehydration, hypothermia, hepatomegaly and pronounced leukopenia. Both animals died a few hours after treatment was initiated. Gross necropsy findings included jaundice, fluid in body cavities, hepatomegaly, splenomegaly, multiple white foci within the liver and spleen, generalized lymph node enlargement and numerous mucosal ulcerations in the colon. Primary histopathological lesions were multifocal hepatic necrosis, splenic necrosis, chronic ulcerative enteritis and diaphragmatic myositis with necrosis and edema. Yersinia enterocolitica was cultured from the liver, spleen, lung, jejunum and rectum. Wild rodents, particularly mice, may have been a source of infection for these animals, as the monkeys were housed in a rural, indoor-outdoor facility. A preliminary culture survey showed that some clinically normal patas monkeys harbored the organism in their intestinal tracts.     

Mating strategy and reproductive success of male patas monkeys (Erythrocebus patas)

Mating behavior and paternity of offspring of wild patas monkeys were studied at Kala Maloue National Park, Cameroon. Observation of patas groups over three years revealed that multi-male situations occurred after takeover of the position of a resident male. Direct observation of behavior showed that resident males (harem males) occupied only 31% of mating in multi-male situations and 100% in one-male situations. DNA-typing revealed that resident males sired two of four of infants in the one-male situation and four of five in the multi-male situation. Under the two years cycle of the one-male situation and the multi-male situation, calculation shows that resident males sired more offspring than sneakers both in observation and paternity testing. Sneak mating occurred during both one-male and multi-male situations, and resident males performed compensatory mating, with dilution of sneaker sperm; these activities explain the discrepancy found between observation of mating and results of paternity discrimination.     

Life-history parameters of a wild group of West African patas monkeys (Erythrocebus patas patas)

Based on long-term, although intermittent, observations (2 years 4 months of 14 years), we present data on birth seasonality, age at first birth, interbirth intervals, mortality rates, age at first emigration, and population change of a wild population of West African patas monkeys (Etythrocebus patas patas) in northern Cameroon. Birth season was from the end of December until the middle of February, corresponding to the mid-dry season. In spite of large body size, the patas females had the earliest age at first birth (36.5 monthsold) and the shortest interbirth intervals (12 months) compared to the closely related wild forest guenons. Age at first emigration of the males was considered to occur between 2.5 and 4.5 years. The group size of the focal group drastically decreased between 1984 and 1987, and steadily increased until 1994, then decreased again in 1997. The neighboring group also showed a similar trend in group size. The population decreases were likely to be caused by drought over 3 years. Annual crude adult mortality rate was 4% during population increase periods (PIP) between 1987 and 1994. It rose to 22% during all the periods (AP), including drought over 3 years. Despite their smaller body size, the rate of the wild forest guenons (Cercopithecus mitis) (4%) was the same and much lower than those of the patas during PIP and AP, respectively. The annual average juvenile mortality rate was 13% during PIP and it also rose to 37% during AP. That of wild forest guenons (C. ascanius) (10–12%) was a little lower and much lower than those of the patas during PIP and AP, respectively. These findings were consistent with Charnov's theoretical model of mammalian life-history evolution in that patas with high adult and juvenile mortality showed early and frequent reproduction in spite of large body size. Charnov also considered high adult mortality as a selective force and high juvenile mortality as a density-dependent consequence of high fecundity. Our results support the former but not the latter research findings.     

Development and mother-infant relations among captive patas monkeys

Generalizations about the rate of behavioral development and mother-infant relations in nonhuman primates are often based largely on observations of a few closely related species of macaques. Patas monkeys (Erythrocebus patas)are sufficiently distant phylogenetically and distinct in their social and ecological adaptations from the well-studied macaque species that observations of their patterns of infant development and mother-infant relations may indicate to what extent macaque patterns are typical of Old World monkey species. Eight patas infants living with their mothers in an established captive group were observed for 960 hr over the first year of life. These infants showed a rapid rate of behavioral development and attainment of independence from mothers. Patas also have one of the fastest rates of sexual maturation of any Old World monkey species. This pattern of rapid social and sexual development can be viewed as a response to a highly seasonal savannah environment in which there is a premium on ability to achieve nutritional, locomotor, and social self-sufficiency as quickly as possible and to reproduce as early and as often as developmental constraints will permit. Patterns of infant development and mother-infant relations may be best understood as an integral part of a species’ overall life history pattern.     

Reproductive performance of a laboratory breeding colony of patas monkeys (Erythrocebus patas)

Reproductive statistics were gathered over a 5½-year period on a colony of Erythrocebus patas. Pregnancies occurred throughout the year under laboratory conditions with a suggestion of a mating peak in the late fall and early winter. Menstrual cycles were monitored and found to average 30.6 days in length. Maximal vaginal cornification occured on day 15 of the cycle suggesting a midcycle ovulation. However, production of timed-mated pregnancies indicated ovulation occurred earlier and that breeding on days 10, 11, and 12 after menstruation was more likely to result in pregnancy. The gestation length was found to average 167.2 days in 142 harem-bred females and 167.5 days in 11 timed-mated pregnancies. Sixty-two percent of all pregnancies resulted in live births; 28% of the conceptions terminated with in-utero death of the fetus. Stillborn infants were delivered in 9% of the pregnancies. Infant mortality during the first 6 months of life was 10.2%. Females raised in the colony conceived their first offspring at approximately 3 years of age and males were able to sire infants at 3 years and 8 months.     

Longitudinal study of dominance relations among captive patas monkeys

Eight and a half years of dominance relations within a captive group of patas monkeys were analyzed. It was found that matrilineal kinship significantly influenced individuals' ranks. In contrast, with the exception of certain intramatriline changes, increasing age had no predictable effect on overall rank, at least for females (this was untestable for males). Offspring typically challenged maternal dominance and in eight of twelve dyads, offspring either rose fully over their mothers (three cases, all daughters) or at least achieved dominance ambiguity with them. Additionally, two of the four younger sisters with an opportunity to rise in rank over an older sister did so. The group dominance hierarchy was unstable for 75% of the study due to a combination of agonistically induced and demographically induced rank changes. Concentration of the highest ranks in a single matriline showed a stronger association with group hierarchy stability than did the presence of an adult, nonnatal male. Group hierarchy stability was associated with increased affiliation (sitting close and sitting touching), but otherwise there were no behavioral correlations. Individuals' ranks within the group hierarchy were unrelated to their chances of being wounded or having diarrhea. Adult females' ranks were over twice as stable as the group hierarchy (57.1% stability), but stability/instability was not correlated with any behavioral changes. Available evidence suggests that dominance relations play only a minor role in the organization of patas monkeys' intragroup behavior. Am. J. Primatol. 42:41–51, 1997. © 1997 Wiley-Liss, Inc.     

Foraging energetics in patas monkeys (Erythrocebus patas) and tantalus monkeys (Cercopithecus aethiops tantalus): implications for reproductive seasonality

The patas monkeys (Erythrocebus patas) in Kala Maloue, Cameroon, have their birth season in the mid-dry season, whereas closely related, sympatric tantalus monkeys (Cercopithecus aethiops tantalus) have their birth season in the wet season. To evaluate the optimality of a species-specific birth season, I estimated the daily intake of available energy and gross protein, and energy expenditure for one individual of each sex of each species between respective birth and mating seasons. The monkeys obtained a larger amount of available energy and gross protein in the birth season than in the mating season. No significant seasonal differences in energy expenditure between the birth and mating season were found. Thus, the birth season appears to be timed to the season when the monkeys can obtain more surplus energy and protein. Interspecific differences in the optimality of birth season were attributed to widely exploitative foraging, supported by the patas' high locomotive ability, which may enable them to obtain more energy from seeds of Acacia seyal and gums of A. sieberiana, and more protein from grasshoppers and seeds of A. seyal in the mid-dry season than the tantalus monkeys. A review of preceding studies suggests that the availability of seeds of Acacia fruiting during the dry season may exert the dominant influence on timing of birth not only in patas but also in savanna monkeys (Cercopithecus aethiops), which include the tantalus monkeys.     

Differential habitat utilization by patas monkeys (Erythrocebus patas) and tantalus monkeys (Cercopithecus aethiops tantalus) living sympatrically in northern Cameroon.

In order to obtain reliable evidence for differences in habitat preferences between two closely related savanna-dwelling primate species, namely, patas monkeys (Erythrocebus patas) and tantalus monkeys (Cercopithecus aethiops tantalus), I collected data on vegetation and patterns of range use concurrently at a single study site, Kala Maloue, Cameroon, in a similar manner for a group of each species. Kala Maloue consisted of 64% grassland mostly dominated by Gramineae spp. and the rest was woodland. Tantalus monkeys showed preference for woodland, especially gallery forest, much more than did the patas irrespective of the season. Moreover, patas preferentially established their home range in grassland in the wet season. Interspecific and seasonal differences in habitat preferences could be interpreted on the basis of interspecific and seasonal differences in preferences for main food. In dry season, tantalus utilized water-containing areas at a frequency closely in proportion to the availability of such areas while the patas utilized water-containing areas more frequently than expected. This is because tantalus established a smaller home range along the river where water was never completely depleted throughout the dry season. Both the patas and the tantalus preferred woodland to grassland as sleeping sites possibly owing to predation avoidance. Both the daily travel distance per group weight and the home range size per group weight were greater for patas than for tantalus partly because of higher preference for grassland with low habitat quality in the case of patas. It is suggested, however, that high locomotive ability enabled patas to effectively utilize small and widely dispersed items of food such as grasshoppers and to explore areas with high availability of food and water and with preferable sleeping sites.     

Body mass distribution and gait mechanics in fat-tailed dwarf lemurs (Cheirogaleus medius) and patas monkeys (Erythrocebus patas)

Most quadrupeds walk with lateral sequence (LS) gaits, where hind limb touchdowns are followed by ipsilateral forelimb touchdowns. Primates, however, typically walk with diagonal sequence (DS) gaits, where hind limb touchdowns are followed by contralateral forelimb touchdowns. Because the use of DS gaits is nearly ubiquitous among primates, understanding gait selection in primates is critical to understanding primate locomotor evolution. The Support Polygon Model [Tomita, M., 1967. A study on the movement pattern of four limbs in walking. J. Anthropol. Soc. Nippon 75, 120-146; Rollinson, J., Martin, R.D., 1981. Comparative aspects of primate locomotion, with special reference to arboreal cercopithecines. Symp. Zool. Soc. Lond. 48, 377-427] argues that primates' use of DS gaits stems from a more caudal position of the whole-body center of mass (COM) relative to other mammals. We tested the predictions of the Support Polygon Model by examining the effects of natural and experimental variations in COM position on gait mechanics in two distantly related primates: fat-tailed dwarf lemurs (Cheirogaleus medius) and patas monkeys (Erythrocebus patas). Dwarf lemur experiments compared individuals with and without a greatly enlarged tail (a feature associated with torpor that can be expected to shift the COM caudally). During patas monkey experiments, we experimentally shifted the COM cranially with the use of a weighted belt (7-12% of body mass) positioned above the scapulae. Examination of limb kinematics revealed changes consistent with systematic deviations in COM position. Nevertheless, footfall patterns changed in a direction contrary to the predictions of the Support Polygon Model in the dwarf lemurs and did not change at all in the patas monkey. These results suggest that body mass distribution is unlikely to be the sole determinant of footfall pattern in primates and other mammals.