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Genetic studies not only contribute substantially to our current understanding of the natural variation in behavior and health in many species, they also provide the basis of numerous in vivo models of human traits. Despite the many challenges posed by the high level of biological and social complexity, a long lifespan and difficult access in the field, genetic studies of primates are particularly rewarding because of the close evolutionary relatedness of these species to humans. The free-ranging rhesus macaque (Macaca mulatta) population on Cayo Santiago (CS), Puerto Rico, provides a unique resource in this respect because several of the abovementioned caveats are of either minor importance there, or lacking altogether, thereby allowing long-term genetic research in a primate population under constant surveillance since 1956. This review summarizes more than 40 years of genetic research carried out on CS, from early blood group typing and the genetic characterization of skeletal material via population-wide paternity testing with DNA fingerprints and short tandem repeats (STRs) to the analysis of the highly polymorphic DQB1 locus within the major histocompatibility complex (MHC). The results of the paternity studies also facilitated subsequent studies of male dominance and other factors influencing male reproductive success, of male reproductive skew, paternal kin bias, and mechanisms of paternal kin recognition. More recently, the CS macaques have been the subjects of functional genetic and gene expression analyses and have played an important role in behavioral and quantitative genetic studies. In addition, the CS colony has been used as a natural model for human adult-onset macular degeneration, glaucoma, and circadian rhythm disorder. Our review finishes off with a discussion of potential future directions of research on CS, including the transition from STRs to single nucleotide polymorphism (SNP) typing and whole genome sequencing. [ABSTRACT FROM AUTHOR]

Female primates endure great costs during pregnancy and lactation. Some studies have been conducted on exploring these; however, information on how maternal condition before conception influences maternal postpartum recuperation and infant development are not well known, especially in primipares. This 2-year investigation explored how maternal condition, maternal foraging time and alert time, and infants' time on nipple influenced postpartum recovery of primiparous rhesus macaques, as well as their infant's development during the first 3 months postpartum. The study was conducted on 11 female rhesus macaques (Macaca mulatta) living at the Caribbean Primate Research Center, Sabana Seca Field Station, Puerto Rico. Infant survivorship and development were not influenced by maternal age at first parturition or by the infants' time on the nipple. Infant development and maternal recovery were influenced by maternal condition before conception. Older primipares demonstrated greater postpartum recuperation. Maternal postpartum recuperation was not influenced by maternal feeding time or time the infant spent on the nipple. Maternal recuperation was negatively correlated with increased vigilance (alert time). Am. J. Primatol. 70:1047–1054, 2008. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

When agonistic interventions are nepotistic, individuals are expected to side more often with kin but less often against kin in comparison with non-kin. As yet, however, few mammal studies have been in a position to test the validity of this assertion with respect to paternal relatedness. We therefore used molecular genetic kinship testing to assess whether adult female rhesus macaques ( Macaca mulatta) from the free-ranging colony of Cayo Santiago (Puerto Rico) bias their interventions in ongoing dyadic aggressive interactions towards maternal and paternal half-sisters compared with unrelated females. It turned out that females supported maternal half-sisters significantly more often than paternal half-sisters or non-kin regardless of the costs associated with such interventions. Similarly, females targeted maternal half-sisters significantly less often than non-kin when this was associated with high costs. Unrelated females provided significantly higher mean rates of both high- and low-cost support to each other than did paternal half-sisters. However, females targeted paternal half-sisters significantly less often than non-kin when targeting was at low cost, suggesting that females refrain from intervening against paternal half-sisters. Our data confirm the general view that coalition formation in female mammals is a function of both the level of maternal relatedness and of the costs of intervention. The patterns of coalition formation among paternal kin were found to be more complex, and may also differ across species, but clear evidence for paternal kin discrimination was observed in female rhesus as predicted by kin selection theory. [ABSTRACT FROM AUTHOR]

Prior to 1985 tetanus was a major cause of mortality in the free-ranging colony of rhesus monkeys on Cayo Santiago, accounting for almost a quarter of annual deaths. In 1985 and 1986 all animals (except infants) received primary and booster doses, respectively, of tetanus toxoid. In subsequent years primary immunizations were given to all yearlings, and boosters were administered to all 2-year-old animals during the annual capture of the colony. The main objectives of the tetanus immunization program were to reduce the pain and suffering caused by tetanus infections and to decrease mortality in the colony. Other objectives were to evaluate the efficacy of the two-dose tetanus toxoid immunization protocol and to determine whether additional boosters might be required to provide adequate long-term protection against tetanus infections. The immediate effect of the mass immunization program was the elimination of clinical tetanus infections in the population and a 42.2% reduction in the overall mortality rate. Since the immunization program began, no cases of tetanus have been observed in the colony, except in two unimmunized infants, and it has not been necessary to give tertiary injections of tetanus toxoid to maintain protection against infection. A sample collected in 2004 of the original cohort of monkeys immunized in 1985 and 1986 showed that 93.3% (14/15) had protective tetanus antibody titers (>0.01 IU/ml) at the ages of 20–23 years, which is close to the life expectancy of the Cayo Santiago rhesus macaques. Two intramuscular doses of tetanus toxoid provided long-term, if not lifelong, protection against tetanus for rhesus monkeys living in a tropical clime where tetanus is enzootic and the risk of infection is great. Am. J. Primatol. 68:725–731, 2006.© 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Rhesus macaque females regularly copulate with a number of partners, and produce a single offspring per reproductive cycle in over 99% of cases. We used genotyping of 10 STR markers to determine paternity in the Cayo Santiago population of rhesus macaques. About 1,500 monkeys have been analyzed to date, with their marker genotypes entered into a computerized database. These data enable us to report the first documented case in any cercopithecine nonhuman primate species of the production of twin offspring sired by different males. Am. J. Primatol. 57:31–34, 2002. © 2002 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Gene conversion and balancing selection have been invoked to explain the ubiquitous diversity of the antigen-presenting proteins encoded in the vertebrate major histocompatibility complex (MHC). In the present study, direct evidence for over-dominant selection promoting MHC diversity in primates is provided by the observation that, in a large free-ranging population of rhesus macaques, males heterozygous at MHC class II locus Mamu-DQB1 sired significantly more offspring than homozygotes (the male-specific selection coefficient s equals 0.34). This heterozygote advantage appeared to be independent of the actual male Mamu-DQB1 genotype. No similar effect emerged for a captive group of monkeys of similar genetic background but under veterinary care. [ABSTRACT FROM AUTHOR]

Body size is associated with menarche and ovarian function, but the relationship to first conception is rarely examined. We conducted a longitudinal investigation of rhesus macaques, Macaca mulatta , to determine the effect of differences in body weight on both the age at first conception and survivorship of first progeny. Young females who became pregnant weighed significantly more than peers who remained barren, with weight changes for females who successfully raised offspring no different than those for females who did not produce offspring. Infant mortality among primiparae was not significantly greater than that among multiparae, although nearly twice as high. First-born males tended to have lower survivorship than first-born female offspring. We suggest that reproductive costs encountered by primiparous females are more likely to be modulated by immature neuroendocrine function than by inexperience, small body size, or infant suckling patterns. We conclude that body size influences probability of first conception, socioendocrine factors mediate the likelihood of infant survival, and primiparous production of male progeny seems to exert a greater reproductive cost than does production of female progeny. Am. J. Primatol. 46:135–144, 1998. © 1998 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The intensity of sperm competition is often measured wing the gonado-somatic index (testes/body weight). But sperm competition could be mediated more by size of the epididymis than by size of the testicles, and little information is available on the relationship between testicular and epididymal size. We found that both organs were positively correlated in size among male rhesus macaques. Body weight accounted far over 70% of variance in testicle size and valumetric estimates of testicle size accurately reflected testicle weight. We conclude that methods for ascertaining tide size are accurate, but the covariation in size between testicles epididymis will hamper understanding of the physiological mechanisms revolved in sperm competition in primates. [ABSTRACT FROM AUTHOR]

The goal of this study was to develop a relatively noninvasive technique for generating ovulatory estrogen levels in cycling females over extended periods of time. Eleven intact cycling rhesus macaques were given weekly injections of estradiol cypionate in an effort to obtain weekly levels which approximated ovulatory levels. A dose of 500 μg generated weekly estrogen values averaging 370 ± 18 pg/ml. This method is a satisfactory alternative to more traditional techniques. It involves no surgical procedures, it is relatively nonintrusive, it does not terminate a female's reproductive career, and it is not as time-consuming as daily injections. Female cycle state can be altered with a minimum of manipulation for studies involving the behavior of estrous females. [ABSTRACT FROM AUTHOR]

Examines the relationship between alarm vocalizations and the endocrine stress response in rhesus macaques. Cortisol as the frequently analyzed hormone in stress-response research; Administration of adrenal steroidogenic inhibitor Metyrapone; Threats used to elicit alarm vocalizations; Differences in the types of alarm vocalization according to treatment.

Levels of aggression may be affected by stability of social relationships or by population density. A number of studies of nonhuman primates have indicated that spatial density influences agonistic activity levels less than does social density. Artificial fissioning of a captive troop of rhesus macaques was undertaken and the resultant differences in patterns of aggression and affiliation were examined. if population density has a major effect on levels of aggression, then fissioning will result in a decrease in aggression; If social stability has a major effect on levels of' aggression, then fissioning is likely to be accompanied by an Increase in aggression. An increase in rates of both aggressive and affiliative behavior resulted from artificial troop fissioning. These findings concur with other studies that have concluded that social stability Is a more important determinant or primate aggression than Is population density. Nonhuman primates use affiliative mechanisms to adjust their behavior when population density increases such Quit potentially adverse consequences of crowding are avoided. [ABSTRACT FROM AUTHOR]

Rape has been posited to be an outgrowth of male reproductive strategies. Forced copulations may have evolved as a consequence of the low parental investment made by males in producing and raising offspring. We designed a laboratory experiment which paired rhesus macaque males with females in order to assess the influence of intersexual aggression on male sexual activity. Younger and older adult males had comparable levels of sexual behavior, but younger males were more aggressive towards females than were older males. In addition, females threatened younger males more than older males. Male attacks on females did not result in sexual intercourse. On the contrary, a negative correlation existed between male aggression towards females and male success at achieving intromissions. Female aggression towards males appeared to be an effective tactic which reduced the chances of sexual intercourse. We conclude that intersexual aggression acts either as a mechanism of dominance assertion or as a means to increase spatial distance between individuals. These data do not support the idea that rape in humans has an evolutionary foundation derived from male reproductive strategies. [ABSTRACT FROM AUTHOR]

Asserts that paternal relatedness and age proximity regulate social relationships among adult female rhesus macaques. Effect of both maternal and paternal kinship, as well as age proximity, on affiliative interactions among semifree-ranging adult female rhesus macaques, Macaca mulatta; Observation pertaining to parental kin discrimination.