Behavioral effects of enrichment on pair-housed juvenile rhesus monkeys

Among captive primates, inanimate environmental enrichment can lead to measurable changes in behavior indicative of an improvement in psychological well-being. Although this has been demonstrated repeatedly for singly caged primates, the relationship is not as well studied for pairhoused animals. Study of the pair-housed setting has become increasingly relevant because of the social housing mandate of the Animal Welfare Act regulations. We therefore observed 68 juvenile rhesus monkeys born in 1988 and 1989 and living in mixed-sex pairs from the ages of 2 to 3 years. All pairs were compatible. Half of the pairs received two types of enrichment, while the remaining pairs served as controls. Enriched and control juvenile subjects differed in the amount of time that they spent being inactive, playing, and drinking, but did not differ in the amount of time they spent interacting with their partner. Grooming and play were the two most common socially directed activities in both groups, a species-appropriate pattern. Males played more and vocalized less than did females. Overall, enriched and control subjects spent equivalent amounts of time located within a social distance of one another, but there was some difference between groups in allocation of behaviors while near the pairmate. Environmental enhancers were frequently utilized, and led to relatively small changes in behavior between control and enriched subjects, suggesting that the presence of a partner for juvenile rhesus monkeys acts as a form of enrichment that may dilute the effects of inanimate environmental enhancements. © 1994 Wiley-Liss, Inc.     

Role of some physical characteristics in species recognition by pigtail monkeys

Three adult pigtail monkeys pressed a lever to see pictures of pigtail and Japanese monkeys with a variety of physical features being removed. The features included head, tail, body, background, and color. The duration and the interval of exposure of these visual stimuli were dependent upon subjects' responding. Preferences for those pictures were evaluated by the ratio of lever-pressing duration to interval of lever-pressing. Two of the subjects showed a consistent preference to see pictures of pigtail monkeys over those of Japanese monkeys. Though this preference tended to maintain when these physical features were removed, it became relatively weak when head and head + tail were removed. These results suggest that pigtail macaques may discriminate species based not on a single characteristics but on some combination of features, and that head may be relatively important than the other features.     

Insights into ovarian function in wild muriqui monkeys (Brachyteles arachnoides)

Fecal samples were collected systematically during a 6-week period, from 13 September-24 October, 1990, from four nonlactating female muriquis (Brachyteles arachnoides) inhabiting an 800 ha forest at Fazenda Montes Claros in Minas Gerais, Brazil. All four females were experienced mothers; one had most recently given birth in June 1988; the other three had most recently given birth in August 1988. Fecal assays measuring progesterone, estradiol, and estrone indicated consistently low levels in the one female who had given birth in June 1988 and in two of the three females who had given birth in August 1988. Elevated steroid levels did, however, appear in fecal samples from the fourth female on day 15 of the collection period. Steroid levels subsequently dropped and then began to rise again during what appeared to be a second cycle. The cycling female was the only one of the four females examined observed to copulate during the collection period. These preliminary data indicate that nonlactating female muriquis do not cycle year-round, resumption of cycling is not tightly synchronized among females even when their prior parturitions were tightly synchronized, and resumed sexual activity appears to be associated with resumed cycling. © 1994 Wiley-Liss, Inc.     

A semi-natural habitat for housing small,nonhuman primates

A semi-natural habitat that was designed to house a social group of squirrel monkeys (Saimiri sciureus sciureus) at Goucher College, in Maryland is described. The design could be readily adapted for use with other small primate species.     

Power and limits of DNA-profiling in primate populations: Paternity assessment in rhesus macaques from Cayo Santiago

Paternity testing was performed in one social group (S) of rhesus macaques from Cayo Santiago, Puerto Rico. In 11/15 cases, sires could be identified comparing the multilocus DNA profiles of 19 males to those of the corresponding mother/child dyads. All 19 males could be excluded from paternity in the remaining four cases. Decision making was partly based on likelihoods of DNA profiles, and the theoretical model underlying these calculation is described. In a second social group (M), held in captivity, paternity testing was impeded by a deficit of maternal bands and by an increased extent of band sharing of mothers and their infants. Some possible explanations for these findings, including increased homozygosity in group M, are discussed.     

How laboratory-raised Japanese monkeys (Macaca fuscata) perceive rotated photographs of monkeys: Evidence for an inversion effect in face perception

Five laboratory-raised Japanese monkeys (Macaca fuscata) were presented various types of photographs of Japanese and rhesus monkeys (Macaca mulatta) in upright, horizontal, and inverted orientations in a sensory-reinforcement experiment. The ratio of the duration of potential viewing time for the photographs which the subjects controlled to the interval between subject-controlled presentations of them (the D/I score) was used as a measure of preference for the photographs. When inverted photographs were presented, the D/I scores were lower than for upright photographs. The difference in D/I scores between photographs of the two species, which indicated discriminability between them, also diminished when the photographs were inverted. The results obtained suggest an inversion effect in face perception in macaque monkeys.     

Mangabey (Cercocebus albigena) population density,group size,and ranging: A twenty-year comparison

Mangabey groups studied in the Kibale Forest Reserve, Uganda, in 1971 were studied again in 1991 using similar data collection protocols. The results were used to assess the effect of group size on activity budgets and travel costs, and to document the effects of habitat changes on mangabey density and demography. Larger mangabey groups traveled longer distances per day than smaller groups. Time budgets were less clearly influenced by group size. Mangabey population density increased over the 20 year period. This increase in population density paralleled habitat changes, particularly an increase in tree density, and was accompanied by increased use of regenerating forest. © 1994 Wiley-Liss, Inc.     

The mitochondrial control region of the black howler monkey,Alouatta caraya (Primates,Platyrrhini), and the development of new primers

The analysis of polymorphic genetic markers is necessary to assess the genetic variability of natural populations in order to develop effective conservation strategies. However, the molecular genetic variability of most neotropical primates is not well known. Therefore, we describe 13 primers for the amplification and sequencing of the mitochondrial control region that were developed for Alouatta caraya. Six of these primers gave unique bands on four other platyrrhine species (Alouatta palliata, Ateles paniscus, Ateles belzebuth and Saimiri boliviensis) showing their utility for control region amplification and sequencing in these platyrrhine species.     

Airborne vs. radio-transmitted vocalizations in two primates: a technical report

Elucidating the structure and function of joint vocal displays (e.g. duet, chorus) recorded with a conventional microphone has proved difficult in some animals owing to the complex acoustic properties of the combined signal, a problem reminiscent of multi-speaker conversations in humans. Towards this goal, we set out to simultaneously compare air-transmitted (AT) with radio-transmitted (RT) vocalizations in one pair of humans and one pair of captive Bolivian grey titi monkeys (Plecturocebus donacophilus) all equipped with an accelerometer – or vibration transducer – closely apposed to the larynx. First, we observed no crosstalk between the two radio transmitters when subjects produced vocalizations at the same time close to each other. Second, compared with AT acoustic recordings, sound segmentation and pitch tracking of the RT signal was more accurate, particularly in a noisy and reverberating environment. Third, RT signals were less noisy than AT signals and displayed more stable amplitude regardless of distance, orientation and environment of the animal. The microphone outperformed the accelerometer with respect to sound spectral bandwidth and speech intelligibility: the sounds of RT speech were more attenuated and dampened as compared to AT speech. Importantly, we show that vocal telemetry allows reliable separation of the subjects’ voices during production of joint vocalizations, which has great potential for future applications of this technique with free-ranging animals.