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PubMed1998

Ontogeny, function, and scaling of the mandibular symphysis in papionin primates.

In vivo study of mastication in adult cercopithecine primates demonstrates a link between mandibular symphyseal form and resistance to "wishboning," or lateral transverse bending. Mechanical consideration of wishboning at the symphysis indicates exponentially higher stresses along the lingual surface with increasing symphyseal curvature. Lengthening the anteroposterior width of the symphysis acts to resist these higher loads. Interspecific adult cercopithecine allometries show that both symphyseal curvature and symphyseal width exhibit positive allometry relative to body mass. The experimental and allometric data support an hypothesis that the cercopithecine mandibular symphysis is designed to maintain functional equivalence--in this case dynamic strain similarity--in wishboning stress and strain magnitudes across adult cercopithecines. We test the hypothesis that functional equivalence during masticatory wishboning is maintained throughout ontogeny by calculating relative stress estimates from morphometric dimensions of the mandibular symphysis in two cercopithecine primates, Macaca fascicularis and M. nemestrina. Results indicate no significant differences in relative stress estimates among the two macaque ontogenies and an interspecific sample of adult papionin primates. Further, relative stress estimates do not change significantly throughout ontogeny in either species. These results offer the first evidence for the maintenance of functional equivalence in stress and strain levels during postnatal growth in a habitually loaded cranial structure. Scaling analyses demonstrate significant slope differences for both symphyseal curvature and width between the ontogenetic and interspecific samples. The distinct interspecific cercopithecine slopes are realized by a series of ontogenetic transpositions in both symphyseal curvature and width. Throughout papionin ontogeny, symphyseal curvature increases with less negative allometry, while symphysis width increases with less positive allometry versus the interspecific pattern. As symphyseal curvature and width are inversely proportional to one another in estimating relative stresses, functionally equivalent stress levels are maintained both ontogenetically and interspecifically, because the relatively slower rate of allometric increase in symphyseal curvature during growth is compensated for by a slower rate of allometric increase in symphyseal width. These results indicate the primacy of maintaining functional equivalence during growth and the need for ontogenetic data in understanding the evolutionary processes that affect form-function relations as well as the interspecific patterning of adult form across a clade.

Analysis of Variance↗

PubMed1997

Development of an enzyme-immunoassay (EIA) for the measurement of follicle-stimulating-hormone (FSH) in Callitrichid primates using a monoclonal antibody against the human-FSH-beta-subunit.

Despite the importance of Callitrichid primates in both biomedical and conservation research, practical and reliable immunoassays for the measurement of follicle-stimulating hormone (FSH) have not yet been described. A panel of monoclonal antibodies against specific peptide fragments within either the alpha or beta subunit of human FSH was evaluated for their ability to recognize FSH from Callitrichid and other New World primates. One of these, monoclonal antibody 46.3h6.b7 raised against human FSH, was selected due to its ability to recognize marmoset monkey FSH and its low crossreactivity with other gonadotrophins. The antibody formed the basis of an enzymeimmunoassay using a highly purified human urinary FSH (Metrodin, Serono) preparation coupled to biotin as label and unmodified as standard. After 24 h incubation, antibody bound label was visualized by addition of streptavidin-peroxidase followed by the appropriate substrate. Parallelism was obtained between the standard and dilutions of pituitary extracts, urine and plasma from the common marmoset (Callithrix jacchus) as well as from two tamarin species (Saguinus fuscicollis and S. oedipus) and one squirrel monkey (Saimiri sciureus). Profiles of plasma and urinary FSH during the follicular phase are shown for two individual marmosets. The ability to measure FSH in Callitrichidae provides new opportunities for studies of the reproductive biology of these New World primate species.

Animals↗

PubMed1997

Milk composition reflects pattern of maternal care in prosimian primates.

Hypothesized relationships between milk composition and life history traits were examined by analyzing mid-lactation milks of seven lemurs (Eulemur fulvus, E. macaco, E. rubriventer, E. mongoz, Varecia variegata, Hapalemur griseus, Lemur catta), three bushbabies (Otolemur crassicaudatus, O. garnettii, Galago moholi), and two lorises (Nycticebus coucang, Loris tardigradus); partial data were also obtained for the lemuroid Cheirogaleus medius. There were no significant differences in milk composition among species within either Eulemur or Otolemur, but the four genera for which multiple samples were available (Eulemur, Varecia, Otolemur, and Nycticebus) exhibited large composition differences. Eulemur milk was, on average, very dilute (9.9% dry matter) and low in energy (0.49 kcal/g). These milks contained 0.9% fat, 1.2% protein, and 8.4% carbohydrate on a fresh weight basis. Protein energy comprised only about 15% of total milk energy. Varecia had significantly higher dry matter (13.5%), fat (3.2%), protein (4.2%), gross energy (0.80 kcal/g), and protein energy:total energy ratio (28%) than Eulemur. Milks of the lorisoid genera Otolemur and Nycticebus were very similar, and both had significantly higher dry matter (18.3, 16.3%), fat (7.6, 7.0%), and gross energy concentration (1.27, 1.13 kcal/g) than either lemuroid genus. Otolemur milk was higher in protein than Nycticebus milk. We conclude that lorises, bushbabies, and perhaps cheirogaleids produce relatively rich, energy-dense milks in comparison with anthropoid primates. However, dilute milks appear to be uniformly found among species of Eulemur and perhaps in Lemur catta. The milk of Varecia (and perhaps Hapalemur) is intermediate in composition. Differences in milk composition among prosimians may be related to differences in maternal care: prosimians that carry their young during lactation produce more dilute milks than do species which leave their young unattended for prolonged periods. When looking at primates as a whole, however, the picture somewhat less clear, since the milks of some "parkers" like Varecia do closely resemble those of large anthropoid primates who carry their young.

Animals↗

PubMed1998

A new pitheciin primate from the middle Miocene of Argentina.

We report here a new fossil primate from the middle Miocene of Argentina. The material consists of isolated teeth, mandibular fragments, and a talus. The fossils were collected in the Collón Cura formation at Cañadón del Tordillo in Neuquén Province. An age of 15.71 +/- 0.07 Ma has been reported for the Pilcaniyeu Ignimbrite, which lies just below the paleosols in which the fossils were found. This material is thus the youngest occurrence of fossil primates in Argentina (hitherto documented in the Santacrucian and older land mammal ages) but still is older than the middle Miocene platyrrhine primates from La Venta, Colombia, in particular the pitheciins Nuciruptor and Cebupithecia. The material is recognized as a new genus and species of Pitheciinae, Propithecia neuquenensis. The mesiodistally compressed, high-crowned incisors are specialized and similar to species in the tribe Pithecini and to the nonpitheciin Soriacebus (early Miocene, Patagonia). We rule out a phylogenetic relationship to the latter because of differences in molar morphology. Propithecia does, however, fit well into the pattern of pitheciin evolution, being more derived than the middle Miocene pitheciin Nuciruptor but not as much as another middle Miocene taxon, Cebupithecia. As such, this makes Propithecia the oldest taxon that can be confidently placed within this modern New World monkey subfamily. By analogy with the molar structures and diets of extant platyrrhines, Propithecia has a molar structure consistent with a variety of low-fiber diets ranging from fruit and gum to seeds. Its incisors suggest seed-eating in much the same way as extant pitheciins, like Pithecia. The talus resembles that of Callicebus, suggesting arboreal quadrupedal locomotion.

Animals↗

PubMed1998

Effects of radio transmitter weight on a small nocturnal primate.

An increasing number of primatologists have begun using radio telemetry to study the behavioral ecology of nocturnal prosimian primates. Radio telemetry has enabled the collection of data on these nocturnal and cryptic prosimians that was previously difficult or impossible to otherwise obtain. A critical assumption of studies employing radio telemetry is that the radio transmitters have no appreciable negative effects on the study animals and the data being collected are not being biased by the presence of radio transmitters. This assumption is made because comparable data from a non-radio-collared control group are impossible to obtain. In an attempt to determine the tolerable weight limit for radio collars for a small nocturnal primate, the spectral tarsier, Tarsius spectrum, a comparison of the behavior and body weight of individuals wearing collars of two different weights was conducted. This study was conducted in Tangkoko Dua Saudara Nature Reserve in Sulawesi, Indonesia. A total of 16 individuals from seven groups were trapped in mist nets, radio-collared, and observed using focal follow sampling between April 1994 and June 1995. Each individual was observed for 4-6 months depending on the life span of the radio-collar battery. The two radiocollar weights appeared not to affect spectral tarsiers differentially. Average body masses in neither set of subjects differed between the days collars were attached and 6 months later, when they were removed. No differences in activity patterns, home range size, or prey capture rate were detectable between subjects wearing the different transmitters. These results suggest that the heavier radio collars used in this study did not have any appreciable effects on the behavioral patterns of this primate.

Animals↗

PubMed1999

Describing behavioral states using a system model of the primate brain.

A system model of the primate neocortex is presented, based mainly on the neuroanatomy of the rhesus macaque monkey and consisting of a set of processing modules arranged as a perception-action hierarchy. These modules correspond to regions of the neocortex and their connectivity to that of the neocortex. A computational approach based on predicate logic is explained, and the results of a computer implementation of the model are reported, which demonstrate social behaviors involving affiliation and social conflict. The behavioral states of primates involved in these behaviors can be represented by the states of the system model, which have a logical representation and a diagrammatic form. It is shown how the behavioral states in goal-directed behaviors can be represented and also their short term moment-to-moment development in time. It is then shown how the state of social interaction among two or more primates can be represented, using their individual behavioral states, with interindividual action and perception. The causal dynamics of behavioral states is explained and also a control mechanism, namely, the use of confirmation signals, which stabilizes behavioral states and their dynamics. Stabilized behavioral states are seen as corresponding to coherent activations of the system, resulting from successful selection of module activations and intermodule communication with confirmation.

Animals↗

PubMed1997

Functional D1 and D5 dopamine receptors are expressed in the suprachiasmatic, supraoptic, and paraventricular nuclei of primates.

In rodents, D1 dopamine receptors are expressed in the suprachiasmatic nucleus and are believed to play important roles in regulating circadian rhythms. It is not currently known if the primate circadian system can be influenced by dopaminergic agents, which have broad clinical use. To determine if dopamine receptors can potentially influence primate circadian function, we examined the expression of D1 dopamine receptors in the anterior hypothalamus of ring-tailed macaques (Macaca nemestrema), baboons (Papto sp.), and humans. Because D5 dopamine receptors also stimulate adenylyl cyclase activity, D5 dopamine receptor expression was studied as well. We used [125I]SCH 23982, which binds to D1 and D5 dopamine receptors, and labeling of the suprachiasmatic (SCN), supraoptic (SON), and paraventricular (PVN) nuclei was detectable in each species. In situ hybridization studies revealed differential expression of D1 and D5 dopamine receptor mRNA in the hypothalamus. D1 dopamine receptor mRNA was expressed in the SCN, SON, and PVN. By contrast, D5 dopamine receptor mRNA was expressed only in the SON and PVN of baboons and humans. Injection of the D1/D5 dopamine receptor agonist SKF 38393 at night increased the uptake of 2-deoxy-D-[14C]glucose in the SCN, SON, and PVN of newborn baboons. By contrast, c-fos mRNA expression was induced in the SON and PVN, but not in the SCN. These data show that D1 and D5 dopamine receptors are present in the hypothalamus of primates and show that activation of these receptors acutely influences SCN, SON, and PVN activity.

Animals↗

PubMed1997

Threat to Humans from Virus Infections of Non-human Primates.

Several hundred distinct non human primate species are recognised, and they are likely to harbour a similar range of viruses to humans. Simians such as cynomolgus and rhesus macaques, African green monkeys, and marmosets are widely used for biomedical research, but despite this extensive close contact very few simian viruses have been shown to pose a threat of infection or illness to humans. Herpesvirus Simiae is the best recognised zoonotic hazard of simians. It is an alphaherpes virus of Asiatic macaques, which causes a mild or subclinical primary infection followed by latency in its natural host. It can be acquired by humans following a bite and causes an ascending meningoencephalitis. Less than 40 human cases have been described and the mortality rate in untreated human infections is 70%. The infection is treatable with acyclovir and extensive guidelines for managing simians and potential exposures have been developed. Ebola virus and Marburg virus have caused epizootics in cynomolgus macaques and vervet monkeys respectively, which have resulted in human infection and fatalities. However, non human primates are unlikely to be their natural host. More recently simian immunodeficiency virus and simian foamy virus have infected researchers, but infection has not been linked to illness. Simian viruses also pose a direct threat to humans through the use of primary monkey tissue cultures in laboratory work and vaccine manufacture, indeed a significant exposure of the human population occurred when cells contaminated with SV40 a polyomavirus of rhesus monkeys were used for polio vaccine production. New medical interventions such as xenotransplantation using primate organs pose a potential risk which requires careful assessment. Copyright 1997 by John Wiley & Sons Ltd.

Journal Article↗

PubMed2000

Converging evidence from microstimulation, architecture, and connections for multiple motor areas in the frontal and cingulate cortex of prosimian primates.

In the present study, somatotopic organization, architectonic features, and patterns of connections were used to define motor areas in the frontal and cingulate cortex of the prosimian primate Galago garnetti. Sites throughout portions of the motor cortex were electrically stimulated with microelectrodes at the approximate depth of layer V. In some of the same animals, injections in primary motor cortex (M1), and in the spinal cord, revealed patterns of connections with physiologically identified motor areas. Results were related to cortical architecture in brain sections processed for Nissl, myelin, cytochrome oxidase, acetylcholinesterase, or neurofilaments. Evidence was obtained for a number of fields previously identified in simian primates, including M1, dorsal premotor field with caudal (PMDc) and rostral (PMDr) divisions, ventral premotor area (PMV), supplementary motor area (SMA), presupplementary motor area (pre-SMA), frontal eye field (FEF), and cingulate motor areas, CMAr and CMAc located rostrally and caudally, respectively. In addition, we distinguished area 6Ds of Preuss and Goldman-Rakic (1991a) between PMV and PMDc, and a more posterior cingulate sensorimotor area (CSMA) with motor connections that may correspond to the supplementary sensory area of monkeys. Areas M1, SMA, PMDc, PMV, CMAr, CMAc, and CSMA projected to the spinal cord, while all of these areas and 6Ds projected to M1. Although area M1 had the lowest stimulation thresholds for evoked movements, movements were also evoked from the other motor areas, as well as from somatosensory areas 3a and 3b. These results indicate that prosimian galagos have a complex of motor areas that closely resembles that in monkeys and suggest that at least 10 motor fields emerged early in primate evolution.

Action Potentials↗

PubMed2002

Single-copy nuclear DNA sequences obtained from noninvasively collected primate feces.

Noninvasively collected primate feces have been shown to provide a useful source of mitochondrial DNA for sequencing and nuclear microsatellite DNA for size analysis. In this study, single-copy nuclear DNA sequences were obtained from noninvasively collected fecal samples of two species of wild tamarins, Saguinus fuscicollis and S. mystax, in the context of a project on the functional utility of color vision. Noninvasive genotyping of the X-linked opsin gene is important for future studies of selection and adaptation at this locus in a number of primate species. The wide range of techniques that can now be applied successfully to DNA extracted from feces introduces a broad spectrum of potential genetic studies that can be undertaken on primates, without the need for intrusive or invasive methods.

Animals↗

PubMed2002

Patterns of lateralized hand use in an arboreal primate, Simias concolor.

Studies of hand use in nonhuman primates suggest that several species exhibit hand preferences for a variety of tasks. The majority of studies, however, focus on the lateralized hand use of captive nonhuman primate populations. Although captive settings offer a more controlled environment for assessing hand preferences, studies of wild populations provide important insights into how handedness is affected by natural environmental conditions and thus potential insights into the evolution of handedness. To investigate handedness in a population of wild nonhuman primates, we studied patterns of lateralized hand use during feeding in four simakobu monkeys (Simias concolor), an arboreal species inhabiting the Mentawai Islands, Indonesia. Our data show that individual variation in hand preferences for feeding existed among our study animals. In addition, each simakobu expressed a significant hand preference for supporting itself on a branch during feeding, an uncoordinated bimanual task. This bias was most prevalent when the branch used for support was a main branch rather than a terminal branch. When both hands were employed in a coordinated bimanual feeding activity (bimanual manipulation), only two subjects showed a significant bias for feeding. Our data suggest that these individuals are more likely to express significant hand preferences when feeding from stable, rather than precarious, positions within the canopy.

Animals↗

PubMed1988

The effects of feedback lighting on the circadian drinking rhythm in the diurnal new world primate Saimiri sciureus.

Feedback lighting provides illumination primarily during the subjective night (i.e., the photosensitive portion of the circadian cycle) in response to a given behavior. This technique has previously been used to test the nonparametric model of entrainment in nocturnal rodents. In three species (Rattus norvegicus, Mesocricetus auratus, and Mus musculus), the free-running period of the locomotor activity rhythm was similar whether the animals were exposed to continuous light or discrete light pulses occurring essentially only during the subjective night (i.e., feedback lighting). In the current experiments, feedback lighting was presented to squirrel monkeys so that light fell predominantly during the subjective night. Feedback lighting was linked to the drinking behavior in this diurnal primate so that when the animal drank, the lights went out. Despite the seemingly adverse predicament, the monkeys maintained regular circadian drinking rhythms. Furthermore, just as the period of the free-running activity rhythms of nocturnal rodents exposed to continuous light or feedback lighting were similar, the period of the drinking rhythms of the squirrel monkeys in continuous light and feedback lighting were comparable (25.6 +/- 0.1 and 25.9 +/- 0.1 hours, respectively), despite a substantial decrease in the total amount of light exposure associated with feedback lighting. The free-running period of monkeys exposed to continuous dark (24.5 +/- 0.1 hours) was significantly shorter than either of the two lighting conditions (P < 0.001). The results presented for the drinking rhythm were confirmed by examination of the temperature and activity rhythms. Therefore, discrete light pulses given predominately during the subjective night are capable of simulating the effects of continuous light on the free-running period of the circadian rhythms of a diurnal primate. The response of squirrel monkeys to feedback lighting thus lends further support for the model and suggests that the major entrainment mechanisms are similar in nocturnal rodents and diurnal primates.

Animals↗

PubMed2007

Plant DNA sequences from feces: potential means for assessing diets of wild primates.

Analyses of plant DNA in feces provides a promising, yet largely unexplored, means of documenting the diets of elusive primates. Here we demonstrate the promise and pitfalls of this approach using DNA extracted from fecal samples of wild western gorillas (Gorilla gorilla) and black and white colobus monkeys (Colobus guereza). From these DNA extracts we amplified, cloned, and sequenced small segments of chloroplast DNA (part of the rbcL gene) and plant nuclear DNA (ITS-2). The obtained sequences were compared to sequences generated from known plant samples and to those in GenBank to identify plant taxa in the feces. With further optimization, this method could provide a basic evaluation of minimum primate dietary diversity even when knowledge of local flora is limited. This approach may find application in studies characterizing the diets of poorly-known, unhabituated primate species or assaying consumer-resource relationships in an ecosystem.

Animals↗

PubMed2002

Variability of metapodials in primates with rudimentary digits: Ateles geoffroyi, Colobus guereza, and Perodicticus potto.

A tenet of evolutionary theory is that, within a species, phenotypic variability is inversely related to the intensity of stabilizing selection. A corollary is that a rudimentary or vestigial structure should be highly variable. This relationship between rudimentation and variability, however, may simply be part of a continuum, as several studies have shown that variability and size of a structure are inversely related. This study tests whether the first metacarpal (MC1) in Ateles geoffroyi and Colobus guereza and the second metacarpal (MC2) in Perodicticus potto are highly variable in their lengths relative to their other metapodials. The former two species have rudimentary thumbs, and the latter species has a rudimentary index finger. Fourteen other species of primates are included in the comparison. The results show that MC1 in A. geoffroyi and C. guereza and MC2 in P. potto are the relatively shortest first and second metapodials, respectively, in this sample of primates. However, an intraspecific analysis shows that neither MC1 in A. geoffroyi and C. guereza nor MC2 in P. potto is significantly more variable than the other metapodials. Nevertheless, an interspecific analysis shows that MC1 in A. geoffroyi and C. guereza is relatively the most variable among the first metapodials (i.e., MC1 and first metatarsal) in this study. MC2 in P. potto, however, is of relatively low variability compared with the other primates. These contrasting results are interpreted in terms of the developmental and evolutionary biology of digits.

Adaptation, Physiological↗

PubMed2004

Genetics and the evolution of primate enamel thickness: a baboon model.

The thickness of mammalian tooth enamel plays a prominent role in paleontology because it correlates with diet, and thicker enamel protects against tooth breakage and wear. Hominid evolutionary studies have stressed the importance of this character for over 30 years, from the identification of "Ramapithecus" as an early Miocene hominid, to the recent discovery that the earliest hominids display molar enamel intermediate in thickness between extant chimpanzees and Australopithecus. Enamel thickness remains largely unexplored for nonhominoid primate fossils, though there is significant variation across modern species. Despite the importance of enamel thickness variation to primate evolution, the mechanisms underlying variation in this trait have not yet been elucidated. We report here on the first quantitative genetic analysis of primate enamel thickness, an analysis based on 506 pedigreed baboons from a captive breeding colony. Computed tomography analysis of 44 Papio mandibular molars shows a zone of sufficiently uniform enamel thickness on the lateral surface of the protoconid. With this knowledge, we developed a caliper metric measurement protocol for use on baboon molars worn to within this zone, enabling the collection of a data set large enough for genetic analyses. Quantitative genetic analyses show that a significant portion of the phenotypic variance in enamel thickness is due to the additive effects of genes and is independent of sex and tooth size. Our models predict that enamel thickness could rapidly track dietary adaptive shifts through geological time, thus increasing the potential for homoplasy in this character. These results have implications for analyses of hominoid enamel thickness variation, and provide a foundation from which to explore the evolution of this phenotype in the papionin fossil record.

Animals↗

PubMed1975

Phylogenetic significance of the skin of New World monkeys (order primates, infraorder Platyrrhini).

The combined properties of a given cutaneous system, like other characters classically employed by systematic zoologists, are useful criteria in the assessment of primate taxonomy and phylogeny. From the synthesis of all available data, it is also concluded that (1) the results define a baseline regarding the normal histology and histochemistry of the skin of most genera and many species of New World monkeys; (2) intrageneric and intraspecific subtleties in cutaneous variation exist in primate integument; (3) single and multiple cutaneous traits contribute to the characterization and accurate identification of most levels of taxa within the primate hierarchy; (4) some traits, however, negate recent taxonomic practices, e.g., the familial position of Callimico; (5) basic cutaneous patterns confirm currently accepted concepts of taxonomy and phylogeny; and (6) the various cutaneous signatures of extant platyrrhines record a history of adaptive radiation in isolation, and suggest that the designation of at least two distinct families is warranted.

Alkaline Phosphatase↗

PubMed1986

Morphometrics of the anterior dentition in strepsirhine primates.

Size variations in the anterior dentition were analyzed for 26 species of strepsirhine primates. The upper and lower incisor rows of strepsirhines, like those of anthropoid primates, scale isometrically with body size. Within the order Primates, strepsirhines exhibit the smallest incisors relative to body size, followed in increasing size by tarsiers, platyrrhines, and catarrhines. If the lateral teeth of the indriid toothcomb are interpreted as incisors and not canines, correlations between mandibular tooth size variables and body weight are maximized. The upper incisors of strepsirhines are extremely small and frequently widely separated, most likely to minimize occlusion with the toothcomb. Species deviations for assorted size variables of the anterior dentition generally fail to reflect functional variations in the use of the anterior teeth; some of the variables, however, do reflect taxonomic differences within the Strepsirhini. Although toothcomb size variations among extant strepsirhines are more readily interpreted in terms of gum feeding and bark scraping than they are in terms of grooming, anterior dental morphology as a whole is more easily explained by a grooming hypothesis when existing models of toothcomb origins are considered.

Animals↗

PubMed1992

Dental microwear and diet in Venezuelan primates.

Recent microwear analyses have demonstrated that wear patterns can be correlated with dietary differences. However, much of this work has been based on analyses of museum material where dates and locations of collection are not well known. In view of these difficulties, it would be desirable to compare microwear patterns for different genera collected from the same area at the same time. The opportunity to do this was provided by the collections of the Smithsonian Venezuelan Project (Handley, 1976), in which multiple primate genera were collected from the same humid tropical forest sites within the same month. The monkeys represent a wide range of dietary preferences, and include Saimiri, Cebus, Chiropotes, Ateles, Aotus, Pithecia, and Alouatta. As in previous microwear analyses, epoxy replicas were prepared from dental impressions, as described by Rose (1983) and Teaford and Oyen (1989). Two micrographs were taken of facet 9 on an upper second molar of each specimen. Computations and analyses were the same as described by Teaford and Robinson (1989). Results reaffirm previously documented differences in dental microwear between primates that feed on hard objects versus those that do not--with Pithecia and Alouatta at the extremes of a range of microwear patterns including more subtle differences between species with intermediate diets. The subtle microwear differences are by no means easy to document in museum samples. However, additional results suggest that 1) the width of microscopic scratches may be a poor indicator of dietary differences, 2) large and small pits may be formed differently, and 3) there are very few seasonal differences in dental microwear in the primates at these humid tropical forest sites.

Analysis of Variance↗