Skeptical responding in rhesus monkeys (Macaca mulatta)

Signalers that misinform sufficiently open may become devalued as sources of information; however, “skepticism” and any comparison involved in testing reliability entail a cost that involves delays and energy expenditure. Skepticism may be less costly though, if, as a rule, animals are not equally skeptical of the signals of all conspecifics. Animals with the ability to recognize individual conspecifics and to recall past encounters with them may have the capacity to restrict skepticism to subsets of animals that are most likely to benefit from deception. We played tape-recorded alarm calls of high- and low-ranking rhesus monkeys(Macaca mulatta) to their groups in a feeding context once daily over 8 consecutive days at the Yerkes Primate Center Field Station. Over the sequence of playbacks, response was greater to the calls of high-ranking monkeys, adult response patterns were different from those of juveniles, and for adults especially, decline in responsiveness was punctuated by partial resurgences of response. These differences may be the consequence of the adults’ more extensive histories of interaction with group members that, though generally reliable, vary with respect to the potential benefits of deceptive signaling.     

High-resolution chromosomes of rhesus macaques (Macaca mulatta)

Late-prophase high-resolution chromosomes were successfully cultured for 22 of 27 Macaca mulatta samples. Twelve of the successful cultures were adequate for karyotyping high-resolution spreads. High-resolution chromosome technique provides an important contribution to primate genetics because it can be used to identify chromosomal anomalies undetected in metaphase spreads and may be useful for paternity exclusion analysis.     

Food-associated calls in rhesus macaques (Macaca mulatta): I. Socioecological factors

Upon discovering food, free-living rhesus macaques (Macaca mulatta)on the island of Cayo Santiago, Puerto Rico, produce a complexof vocal signals consisting of five acoustically distinguishablecalls. This report examines the socioecological factors elicitingcall production and the information protentially conveyed toothers. The primary contexts for three vocalizations ("warbles," "harmonicarches, " and "chirps") are encounters with rareand highly preferred foods (e.g., coconut). Two other vocalizations("coos" and "grunts") are produced both in food (primarily provisionedchow) and in nonfood contexts, such as during mother-infantseparation and grooming interactions. Grunts given upon encounteringfood are acoustically distinct from those given in nonfood contexts.In contrast, coos associated with food are statistically indistinguishablefrom coos given in other contexts. When conspecitics hear thesefood-associated calls, they typically approach the caller. Coosare less likely to lead to approach than other food-associatedcalls, Results from all-day follows on adult males and adultfemales reveal that changes in hunger level influence call ratebut not call type; the different call types are produced throughoutthe day. We infer that the structure of food-associated callsprovides information about the quality of the food discovered,whereas call rate conveys information about the relative hungerlevel of the caller. In this population, adult males give fewerfood-associated calls than adult females. In addition, femaleswithin large matrilines call more than females within smallermatrilines, and males who are resident in a group are more vocalthan peripheral males.     

Geophagy as a therapeutic mediator of endoparasitism in a free-ranging group of rhesus macaques (Macaca mulatta)

Parasite levels were determined for 141 members of a naturally formed social group of rhesus macaques living under free-ranging conditions. Results indicate that group members harbor Trichuris trichiura, Balantidium coli, and large numbers of Strongyloides fuelleborni. Parasite counts decrease significantly with age in this population. Females have significantly fewer parasites than males and a significantly lower prevalence of multiple infections. There were no rank effects regarding parasitosis. While 89% of the animals examined are infected with one or more species of enteric parasite, the prevalence of diarrhea is negligible (2%). The low prevalence of diarrhea in the presence of high parasite loads may be due to the practice of geophagy, which is engaged in by 76% of group members. Soil eaten by these monkeys contains large amounts of kaolinitic clays. Kaolin-based pharmaceuticals (i.e. Kaopectate^®) are commonly used in human populations to treat diarrhea and intestinal upsets. The mechanical and pharmaceutical properties of the natural kaolinite-based clays may counteract the effects of parasitosis in this free-ranging population. Am. J. Primatol. 44:71-82, 1998. © 1998 Wiley-Liss, Inc.     

Fetotoxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for rhesus macaques (Macaca mulatta)

The fetotoxic and teratogenic potential of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for rhesus macaques (Macaca mulatta) was tested through oral administration to monkeys early in pregnancy. A single or divided dose, 1 μg of TCDD/kg of body weight, was followed by abortion in 13 of 16 pregnant monkeys treated between days 20 and 40 of gestation. One of four aborted at 0.2 μg/kg, and two of two at 5 μg/kg. None of the mothers given 0.2 μg/kg showed signs of toxicity. Eight of the monkeys aborting at 1 μg/kg showed clinical toxicity 44 to 111 days after aborting, and three died. Both given 5 μg/kg became toxic soon after abortion and died. No malformations except for two minor palatal abnormalities of questionable significance were found in the six fetuses that were not aborted at doses of 0.2 and 1.0 μg/kg. These results indicate (1) that TCDD is fetotoxic at doses that frequently have delayed toxicity to the mother, but that conclusions about teratogenicity cannot be drawn, and (2) that pregnant rhesus females are more sensitive to the toxic effects of TCDD than any species tested but the guinea pig.     

A microagglutination test for blood typing rhesus monkeys, Macaca mulatta

Summary. We have developed a microagglutination test for typing rhesus monkey erythrocytes that is sensitive, accurate and easy to perform. The technique requires only μ1 quantities of antiserum and cells, and agglutination is easily detected using an inverted microscope. An advantage of this technique is that the typing plates can be stored at -70°C without loss of activity. The results of typing over 400 rhesus blood samples with this technique were 95% concordant with results using the standard microtitre agglutination technique. Preliminary results indicate that this test is also adaptable to typing human blood.     

Age estimation in rhesus macaques (Macaca mulatta) based on mandibular dimensions

A new technique has been developed for estimating age in rhesus macaques (Macaca mulatta) that is based on mandibular measurements and has several advantages over presently available techniques. First, the new technique is relatively quick and inexpensive because a single measurement or radiograph suffices to produce an age estimate. Second, mandibular growth represents a more continuous phenomenon than either epiphyseal union or dental eruption; therefore, age estimates may be made throughout the period of growth without significant gaps in the process. Finally, the new technique may be used on incomplete or even fragmentary skeletal material because it requires that only a portion of the mandible be preserved. The new technique produces age estimates with a prediction error of ±5.08 months in males and ±7.29 months in females. These errors are only slightly higher than those found previously for dental eruption or epiphyseal union data.     

Food-associated calls in rhesus macaques (Macaca mulatta): II. Costs and benefits of call production and suppression

In field experiments, free-ranging rhesus macaques (Macaca mulatto)gave food-associated calls in 45% of the trials in which theywere presented with food, either monkey chow or coconut; theydid not call in control trials when sticks were presented. Consistentwith prior naturalistic observations, adult females called ina higher proportion of trials than adult males. Coconut, oneof the most highly preferred food items in the diet, eliciteddifferent call types and a higher rate of calling from "discoverers"than did chow. The call types produced to coconut (warbles,harmonic arches, and chirps) were primarily those that, undernonexperimental conditions, were associated with relativelyrare and preferred foods. In contrast, coos and grunts wereprimarily produced in response to chow. The relative hungerlevel of the discoverer had no significant effect on the calltype produced but did affect the rate of call production; discovererscalled at higher rates when they were hungry. Upon hearing food-associatedcalls, individuals within the vicinity of the discovery respondedby rapidly approaching the caller. A larger number of individualsapproached when discoverers called than when they did not. Discovererswho failed to call received significantly more aggression fromgroup members and, in the case of females, actually consumedless food than discoverers who called. The probability of receivingaggression did not appear to be associated with the discoverer'sdominance rank. Results suggest that food-associated calls are"honest" signals reflecting food possession. Those who failto signal and are caught with food are apparently punished.     

Normative nerve conductions in the tail of rhesus macaques (Macaca mulatta)

BACKGROUND: The aim of this study was to test the feasibility of using the tail of Macaca mulatta for neurophysiological testing of the peripheral nervous system. METHODS: Motor and sensory nerve conduction studies (NCS) of the tail were obtained by surface stimulation and recording. The technique utilized was novel. Unlike other NCS obtained from other peripheral nerves, this technique did not require any special neurophysiological expertise. RESULTS: The latency of the motor and sensory response was 2.5 +/- 0.71 and 1.1 +/- 0.27 ms respectively. The amplitude of the motor and sensory response was 8.1 +/- 5.1 mV and 14.6 +/- 9.4 microV respectively. Similar to human beings, there was a statistically significant relationship between age and motor amplitude, motor latency and sensory latency. CONCLUSIONS: Based on our results, a relatively simple, reproducible neurophysiological monitoring technique of the peripheral nervous system is possible.     

Genetic variation in transferrin alleles of rhesus macaques, Macaca mulatta

The rhesus macaque displays an extensive polymorphism at the transferrin locus. A principal components analysis describes the variance and covariance of alleles at the transferrin locus in eight widely dispersed sample populations. Using an eigenvectorial representation of the covariance matrix and systematically approximated geographical locations the distribution of populations and transferrin alleles is compared. Alleles with high variance prove to be the determining factor in the placement of populations in a "genetic map" and provide a means for interpreting the low congruence of genetics and geography found.     

Antibody responses to two encephalomyocarditis virus vaccines in rhesus macaques (Macaca mulatta)

Abstract: Two groups of rhesus macaques (Macaca mulatta) housed in rodent-controlled outdoor corrals were inoculated with two different encephalomyocarditis virus (EMCV) vaccines. One group (n = 45) received a vaccine made from an inactivated field isolate of virus cultured during an outbreak at a zoo in Florida. This vaccine produced fourfold increases in the titers of 28 animals (62%); the increases persisted for at least 18 months (last test) after a single injection of the vaccine. The other group (n = 51) received a vaccine made from an inactivated porcine field strain of the virus. This vaccine did not produce titers in any of the vaccinees.     

Aspects of fight interference in free-ranging and compound-dwelling rhesus macaques (Macaca mulatta)

Patterns of fight interference (agonistic aiding) were compared among three groups of rhesus monkeys (Macaca mulatta) living in two settings: (1) two groups at Cayo Santiago (Caribbean Primate Center); and (2) one group at the Yerkes Regional Primate Research Center (YRPRC). A total of 1,227 interference episodes were recorded in 1,650 hours of observation. The only significant intergroup difference was the increased tendency of males at YRPRC to aid aggressors rather than victims. Among other findings, females aided relatives, interfered against target animals dominant to themselves, aided juveniles, and aided victims more consistently and frequently than did males. Importantly, female interference became more male-like in pattern when aid was given to nonrelatives. Neither the dominant males nor males in general displayed a unique or consistent tendency to interfere in fights in a manner which could be interpreted as controlling aggression. The males' interference patterns also did not suggest they were forming coalitions to either attain or defend status rankings. It is concluded that, overall, observations of compound-dwelling and free-ranging rhesus monkeys reveal similar relationships. Further, while female rhesus monkeys interfered in fights in a manner consistent with the control of aggression and protection of kin, the motives of male interferers remain unknown; however, their behavior is consistent with the hypothesis that they were reducing intermale tensions while, at the same time, minimizing physical risk.     

Demodex spp. in the hair follicles of rhesus macaques (Macaca mulatta)

The perineal or perineal and facial skin were evaluated on 53 rhesus macaques as part of a necropsy protocol. Microscopic evaluation of H & E stained skin sections revealed 19 animals positive for Demodex spp. Mites were seen within all portions of the hair follicles. Infestation varied from minimal to severe. Mites were found in macaques of all ages and in both sexes. Reaction to the mites ranged from no reaction, to minimal follicular epidermal hyperplasia to furunculosis. Immune status of the animal did not determine infestation but immune compromised macaques had more severe lesions. This is the first known report of Demodex spp. in rhesus macaques.     

Genetic characterization of Indian-origin and Chinese-origin rhesus macaques (Macaca mulatta)

Genetic differences between Indian-origin and Chinese-origin rhesus macaques are as great as those between some primate species and can influence the results of experiments in which both are used as animal models for the study of the same human diseases. Unfortunately, many breeding facilities do not know with certainty the origin of the founders of their rhesus breeding colonies. Here I summarize the most definitive of the genetic traits among the microsatellite (STR) loci and mitochondrial DNA sequences that my laboratory previously reported to characterize Indian-origin and Chinese-origin rhesus macaques and then estimate the frequencies of these traits and their reliability as indicators of country of origin. The expression of diagnostic traits at two or more of four different unlinked loci provides a nearly 100% reliability in distinguishing rhesus macaques of Indian and Chinese origin.     

Assessment of genetic management at three specific-pathogen-free rhesus macaque (Macaca mulatta) colonies

Genetic management is required to maintain genetic diversity by minimizing inbreeding and genetic subdivision in colonies of animals bred for biomedical research. Polymorphic short tandem repeat (STR) loci are useful for genetic management because they facilitate parentage assignments, genetic characterization of individuals, and estimates of baseline population genetic parameters. Using highly informative STR loci, we estimated gene diversity and F-statistics to determine the level of genetic heterogeneity and genetic structure of three specific-pathogen-free (SPF) rhesus macaque (Macaca mulatta) colonies. Effective population sizes, variance in male reproductive success, and rate of decrease in genetic variability also were estimated for two of the three colonies. We documented the overall success of genetic management in maintaining genetic diversity in captive colonies. We report that even genetically managed SPF colonies, despite maintaining high and stable levels of gene diversity (over 0.75), are prone to genetic subdivision due to different management strategies, founder effects, genetic isolation, and drift. These processes are accelerated by the high variances in male reproductive success and low adult sex ratios that are typical of captive rhesus macaque breeding groups, both of which reduce the effective population sizes of these groups.     

Gestation length in rhesus macaques (Macaca mulatta)

We describe some of the sources of variation in gestation length among rhesus macaques. the data were obtained from the timed-mating breeding program at the California Regional Primate Research Center (CRPRC). Information about approximately 700 pregnancies that resulted in spontaneous vaginal deliveries of liveborn young is presented. The average length of these pregnancies was 166.5 days. In this population, older females with higher parities had significantly longer pregnancies and significantly heavier infants than other females did. Other factors, including infant sex, month of conception, maternal reproductive history, and paternal identity, had no consistent effect upon gestation length.     

Decrease in sexual initiative and responsiveness in female rhesus macaques (Macaca mulatta) during pregnancy

Although the sexual behavior of female rhesus macaques (Macaca mulatta) has been reported to decrease during pregnancy, systematic studies have been largely confined to reports of male behavior. Therefore, we designed a study to examine changes in female sexual behavior during pregnancy. Six cycling multiparous female rhesus macaques were paired during the periovulatory period of the menstrual cycle and during the first and second halves of pregnancy with six sexually experienced males of the same species. Each female was paired with the same male in all tests. The means of the behavioral measures scored on days 11–13 of the menstrual cycle, 35–56 of pregnancy, and 147–168 of pregnancy were compared. Females showed a significant decrease in the present contact ratio and the rate of threat-aways during pregnancy. Males showed lower rates of threatening-away, contacting, mounting, intromitting, and ejaculating when females were pregnant. The extent to which the decrease in male sexual behavior can be accounted for by an increase in female rejection is uncertain, but it is probably as significant as any loss of attractiveness that might accompany pregnancy.     

The human-ABO blood groups of free-ranging long-tailed macaques (Macaca fascicularis) and parapatric rhesus macaques (M. mulatta) in Thailand

BACKGROUND: Long-tailed and rhesus macaques are widely used in biomedical research; therefore, the known blood group is important. METHODS: The human-type ABO blood group was determined in wild or semi-wild long-tailed and rhesus macaques in Thailand. A total of 729 long-tailed and 160 rhesus macaques from 20 localities were temporarily caught. RESULTS: The frequency profiles of blood groups, calculated by averaging the frequency of each troop in long-tailed and rhesus macaques, were AB > O > B > A at 29.6%, 27.4%, 27.2%, and 15.8%, and B > AB > A > O at 39.6%, 33.4%, 18.2%, and 8.8%, respectively. Irrespective of locality, the frequencies were AB > O > B > A of 29.6%, 28.0%, 24.4%, and 18.0%, and AB > B > A > O of 37.5%, 28.7%, 26.9%, and 6.9%, respectively, for all long-tailed and rhesus macaques. The frequency profile of blood groups in Thai rhesus macaques was somewhat similar to that in the parapatric long-tailed macaques; however, it was different from other rhesus populations where only group B was detected. CONCLUSIONS: Our data support the hypothesis that Indochinese rhesus macaques are hybrids between rhesus and long-tailed macaques in the past.     

Colonic adenocarcinoma in a rhesus macaque (Macaca mulatta)

Abstract: A spontaneous colonic adenocarcinoma and endometriosis was diagnosed in a 34-year-old female rhesus macaque (Macaca mulatta). The tumor caused partial obstruction of the ascending colon and histologically resembled the commonly described napkin-ring tumors of the descending and sigmoid colon found in humans. Serum levels of CA 125, a high-molecular-weight glycoprotein antigen that has been reported elevated in a variety of pathological conditions of the pelvic cavity in humans, was severely elevated. Both the adenocarcinoma and the endometriosis may have contributed to this finding.