Preliminary observations on squirrel monkey (Saimiri oerstedi) vocalizations in Costa Rica

This study was an initial attempt to analyze quantitatively vocalizations from the Central American squirrel monkey, Saimiri oerstedi. Vocalizations were recorded in the wild at P. N. Corcovado (S. o. oerstedi). and at P. N. Manuel Antonio (S. o. citrinellus). Additional recordings were made from captive individuals of both subspecies. The acoustic structure of analyzed vocalizations resembled most closely the vocal repertoire of South American Saimiri with the “gothic arch” phenotype, in agreement with the prominent gothic arch facial pattern of S. oerstedi. New structural subtypes of the twitter (“dog-tooth twitter”) and the chuck (“bent-mast chuck”) not previously found in an extensive library of South American Saimiri sound spectrograms were documented. Calls used by older infants when socially separated and when approaching an adult male were essentially identical (sharing typical “isolation peep” structural features) but had significantly different duration and peak frequency. Analysis of recordings from an escaped captive female calling outside her compound over a 3-day period indicated the presence of numerous structural intermediates between typical chuck, twitter, and peep calls.     

Taxonomy of squirrel monkeys genus Saimiri (cebidae,platyrrhini): A preliminary report with description of a hitherto unnamed form

Two groups of squirrel monkeys, genus Saimiri, are distinguished by external characters. The first, or Roman type, contains Saimiri boliviensis of upper Amazonia south of the Rio Marañón-Amazonas, with two subspecies of which S. boliviensis peruviensis is described as new. The second group, or Gothic type, contains three species: Saimiri sciureus with four subspecies distributed over much of tropical South America, Saimiri ustus of Brazil between the south bank Amazonian Rios Purús and Xingu, and S. oerstedi isolated on a Pacific coastal area straddling Costa Rica and Panamá. The geographic range of S. sciureus overlaps parts of those of S. ustus and S. boliviensis. Incomplete karyotypic data indicate that the diploid number of chromosomes for the genus is 44. Geographic variation is characterized by reduction from seven to six or five paired acrocentric autosomes through pericentric inversion with reciprocal increase in number of paired submetacentric or subtelocentric autosomes. Geographic distribution, behavior, sexual dimorphism including dichromatism, and hybridization are discussed. Ventral guide hairs for orientation of subprecocial newborn toward the maternal mammae are described. Distinguishing characters of species and subspecies are provided in a key. The taxons are listed with the taxonomy of each discussed, their geographic distribution plotted and mapped.     

Taxonomy of squirrel monkeys genus Saimiri (Cebidae,platyrrhini): A preliminary report with description of a hitherto unnamed form

Two groups of squirrel monkeys, genus Saimiri, are distinguished by external characters. The first, or Roman type, contains Saimiri boliviensis of upper Amazonia south of the Rio Marañón-Amazonas, with two subspecies of which S. boliviensis peruviensis is described as new. The second group, or Gothic type, contains three species: Saimiri sciureus with four subspecies distributed over much of tropical South America, Saimiri ustus of Brazil between the south bank Amazonian Rios Purús and Xingu, and S. oerstedi isolated on a Pacific coastal area straddling Costa Rica and Panamá. The geographic range of S. sciureus overlaps parts of those of S. ustus and S. boliviensis. Incomplete karyotypic data indicate that the diploid number of chromosomes for the genus is 44. Geographic variation is characterized by reduction from seven to six or five paired acrocentric autosomes through pericentric inversion with reciprocal increase in number of paired submetacentric or subtelocentric autosomes. Geographic distribution, behavior, sexual dimorphism including dichromatism, and hybridization are discussed. Ventral guide hairs for orientation of subprecocial newborn toward the maternal mammae are described. Distinguishing characters of species and subspecies are provided in a key. The taxons are listed with the taxonomy of each discussed, their geographic distribution plotted and mapped.     

Effect of separation distance on isolation call structure in squirrel monkeys (Saimiri sciureus)

Isolation calls of captive squirrel monkeys were recorded by separating infants from their natal group members and then permitting vocal contact between the “lost” baby and the group at systematically varied distances. Separated infants gave longer calls at greater separation distances from their natal group members, and responding adults and juveniles similarly extended the length of their vocalizations. In the longer variants, a highfrequency element was prolonged, which is considered to be an example of the net advantage of a “frequency window” in the ambient noise of environments.     

Abnormal behaviors in nursery-reared squirrel monkeys (Saimiri sciureus)

Seventeen squirrel monkeys (Saimiri sciureus), 11 nursery-reared and six mother-reared, were monitored to clarify the type and degree of deviant behaviors that result from rearing this species in the nursery. Two observation periods were used: the first when the subjects averaged 6.7 months of age, the second when they averaged 15.5 months. Thirteen activities involving variations of nonnutritive orality, stereotypic posturing, and agitated behaviors were seen in the nursery-reared subjects, but never in the mother-reared subjects. No consistent gender, subspecies, or age differences were evident. Squirrel monkeys, like chimpanzees and some Old World monkeys, do develop atypical self-directed behaviors when deprived of normal stimulation during early development.     

A study of postnatal appendicular skeletal maturation in captive-born squirrel monkeys (Saimiri boliviensis)

This study is based on a mixed longitudinal radiographic sampling of appendicular bones in 82 captive-born squirrel monkeys (Saimiri boliviensis). All appendicular ossification centers had appeared radiographically by 17 weeks of age, and epiphyseal fusion was complete by 47-53 months of age. No statistically significant differences were found between the sexes in comparisons carried out at birth and at 6 and 8 months of age. Valid sex comparisons could not be made at other ages owing to the small size of the sample. The sequence of appearance of the ossification centers (Spearman correlation coefficient of Saimiri vs. Callithrix = 0.68) shows greater interspecies differences than the sequence of fusion (Saimiri vs. Callithrix = 0.88).     

Susceptibility of squirrel monkey (Saimiri sciureus) to infection by mammalian schistosomes.

In a study of host-schistosome relationships, the squirrel monkey (Saimiri sciureus) was exposed to 500 cercariae of Schistosoma bovis (Kenya), S. intercalation (Cameroon), S. mattheei (South Africa), 2 strains of S. mansoni (Puerto Rico and South Africa), 2 strains of S. rodhaini (Uganda and Kenya), and Schistosomatium douthitti (North America). It is apparent that the squirrel monkey can be employed as an experimental host for a broad range of mammalian schistosomes. Based upon cercariae-adult worm ratios, it is a good host for S. intercalatum, S. mattheei, the Puerto Rico and South Africa strains of S. mansoni, and Schistosomatium, but only a fair host for S. bovis and the Uganda and Kenya strains of S. rodhaini. Individuality of host-parasite relationships is borne out by the great ranges recorded for egg deposits in different organs as well as by total body egg counts and eggs/worm pair.     

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.     

A study of correlates of hand preferences in squirrel monkeys (Saimiri sciureus)

The purpose of this study was to test the influence of sex, age, social rank, matriline membership, posture, and visual and tactual motor control on manual preferences inSaimiri sciureus. A well-established social group of 12 squirrel monkeys, aged 2 to 14 yrs and consisting of two matrilines with social rank known for each animal, was presented with four different food-reaching tasks and assessed for hand preferences with a minimum of 100 reaches per animal. Frequency of occurrence of hand preferences at the group level and degree of hand preferences at the individual level depended on posture and on whether the reaching act took place under visual or tactual guidance. Sex, age, social rank, and matriline membership were not found to determine frequency of occurrence, direction or degree of hand preferences with the exception of one task in which a significant negative correlation between the degree of hand preference and age was found. Nine out of 12 monkeys showed task-dependent changes in the hand they used preferentially while only three animals preferred the same hand in all four tasks. Significant preferences for the use of right or left hand on a given task were distributed almost equally between individuals. Thus, the results of this study suggest task-specific demands like posture and/or whether reaching was visually or tactually guided to be the major correlates of hand preferences in food-reaching tasks in squirrel monkeys.     

Taste preference thresholds for food-associated sugars in the squirrel monkey (Saimiri sciureus)

The purpose of this study was to determine taste preference thresholds for four different food-associated sugars inSaimiri sciureus. Using a two-bottle test three male squirrel monkeys were found to significantly prefer 10 mM sucrose, 40 mM fructose, 90 mM glucose, and 100 mM lactose over tap water. Presentation of suprathreshold sugar solutions led to marked concentration-dependent and monotonically increasing polydipsia. The results showed the squirrel monkey to prefer lower sugar concentrations compared to other non-human primates and thus support the assumption that this species may use sweetness as a criterion for food selection.     

The effect of relative humidity on osmoregulation in the squirrel monkey (Saimiri sciureus)

Osmoregulatory balance was studied in four young, tamed squirrel monkeys (Saimiri sciureus, Columbia) after acclimatization to relative humidities (rh) commonly used in laboratories (30% and 50%) and to higher humidities representative of the dry and wet seasons in their natural environment (75% and 95%). The temperature was constant at 25°C and the light-dark cycle was 12:12 hours. The animals were maintained in large metabolism cages and were free moving. Water consumption and urine flow rates increased at each higher humidity from 30% rh to 75% rh and then decreased at 95% rh (p<0.05). Fecal water loss was greater with higher humidity (p<0.05). Evaporative water loss remained relatively constant until a break between 75% and 95% rh, at which point it decreased dramatically (p<0.05). Expressed relative to total water intake, evaporative water loss demonstrated a progressive decrease with increasing humidity: 65%, 56%, 51%, and 42%, at 30%, 50%, 75%, and 95% rh. This indicates that as the humidity approaches maximum saturation, not only is the evaporative water loss component necessarily diminished, but also the apparent precipitation of alternate strategies of thermoregulation leads to a reduction in the overall water requirements of the animals. Potassium/sodium excretion ratios were relatively constant at 30%, 50%, and 95% rh but decreased significantly at 75% rh (p<0.05). As a reflection of adrenocorticosteroid activity, this suggests that at 25°C, 75% rh is an optimal humidity in the maintenance of squirrel monkeys. The significant osmoregulatory alteration occurring between 75% and 95% rh provides further evidence that relative humidity may be an important factor in the seasonal physiological cycles of the squirrel monkey. In conducting the research described in this report the investigators adhered to the “Guide for Laboratory Animal Facilities and Care,” as promulgated by the Committee on the Guide for Laboratory Animal National Academy of Sciences, National Research Council.     

Morphometric analysis of the zona pellucida and ooplasm of squirrel monkey (Saimiri sciureus) eggs

The objective of this study was to correlate the thickness of the zona pellucida (zona) with egg (oocyte) maturity determined through a widely-used method of assessing oocyte maturation namely, the evidence for cumulus and corona cells expansion. Measurements of the zona of cultured oocytes were recorded at 0, 3, 6, 24, and 48 hr after laparoscopic oocyte retrieval from hormonallystimulated squirrel monkeys. The results indicated that at the time of oocyte retrieval, oocytes that were classified as mature had thicker zonae compared with immature oocytes. The zona layer of the mature oocyte expanded to a maximum after 6 hr of incubation while the zona layer of the immature oocyte became compressed. The diameter of the mature oocyte (minus the zona and perivitelline space) became smaller with time while the immature oocyte diameter remained relatively unchanged. The correlation between the maturational state of the oocyte and the thickness of the zona layer suggest the possible application of zona morphometric evaluations as an indicator of oocyte maturation.     

Diurnal variations of androgens in sexually mature male Bolivian squirrel monkeys (Saimiri sciureus) during the breeding season

To assess diurnal fluctuations of serum androgens and cortisol in adult male Bolivian squirrel monkeys, these steroids were measured at predetermined times (0300, 0900, and 2300 hours) during two separate 24-hour periods in the breeding season (January 1983 and late November 1983). A significant diurnal change in serum cortisol was noted, with a nadir of 99.9 ± 11.9 μg/dl (x? ± SEM) at 2300 hours and a peak of 168.9 ± 7.8 μg/dl at 0900 hours. Conversely, a nadir in serum testosterone was noted at 0900 hours (117 ± 26.5 ng/ml) increasing to a peak of 328.5 ± 57.9 ng/ml at 0300 hours. Serum androstenedione and dehydroepiandrosterone followed a pattern similar to testosterone, with a serum androstenedione (176.4 ± 34.9 ng/ml) and dehydroepiandrosterone (11.7 + 1.8 ng/ml) nadir at 0900 hours and a plasma androstenedione (494.5 ± 55.4 ng/ml) and dehydroepiandrosterone (32.5 ± 4.1 ng/ml) peak at 0300 hours. Parallel changes of testosterone, androstenedione, and dehydroepiandrosterone suggest a significant contribution of all three androgens from a common site, the testes. In contrast to old world primates and humans, serum androstenedione levels exceeded serum testosterone levels in this species.     

ABO Blood groups in cebidae (Platyrrhini,Primates) from the Rio Jamari Region

Blood and saliva samples were collected from 84Aotus azarae boliviensis, 31Ateles paniscus chamek, 130Callicebus brunneus, 130Cebus apella, 117Pithecia irrorata irrorata, and 117Saimiri ustus. Saliva samples were investigated for human ABH antigens by the standard hemagglutination inhibition test. Two species,P. irrorata andC. brunneus showed monomorphism, presenting only the A blood group. Among the polymorphic species,A. paniscus andC. apella presented theO (30 and 3) and A (1 and 127) phenotypes, and the B (80) and AB (4) phenotypes were detected inA. azarae. S. ustus was the only species that presented all the four phenotypes. The observed distribution was as expected assuming Hardy-Weinberg equilibrium to be present in those species that could be tested. The ABH substances were titrated and a comparison among species was made. Serum samples were used to detect natural antibodies and the results showed some disagreement between serum and saliva phenotypes.     

Cross-sectional morphometric data on a population of semifree-ranging squirrel monkeys,Saimiri sciureus (Iquitos)

Eight morphometric measurements and weights were taken on 169 members of a semifree-ranging population of squirrel monkeys, Saimiri sciureus (Iquitos), at the MonkeyJungle, Goulds, Florida. Age- and sex-related differences were determined. Weight and brow-rump length correlated most highly with age. Sexually dimorphic differences were particularly evident in weight and head width, and both of these showed seasonal variation in the males.     

The subfossil monkey femur and subfossil monkey tibia of the Antilles: A review

The proximal portion of a subfossil monkey femur found in a Jamaican cave shares all the femoral characters of a mature male Cebus apella.The fragment alone, however, does not prove conspecificity. The Jamaican femur is also of a size that could belong to the extinct Xenothrix mcgregoriof the same island. In contrast, the distal portion of a monkey tibia recovered from a kitchen midden in the Dominican Republic cannot be identified with that of any known living platyrrhine or catarrhine monkey. Geological age, geographic locality, and size of fragment point to probable alignment of the tibia with the recently extinct cebid Saimiri bernensis.Although no conclusive identifications are made, the distinctive characters of the two limb bones are described on the basis of comparisons with femurs and tibias representing all genera of living platyrrhines, most genera of catarrhine monkeys, and some strepsirhines.     

Wild squirrel monkey (Saimiri sciureus) “caregiver” calls: Contexts and acoustic structure

A field study of the vocal behavior of 22 wild adult female squirrel monkeys (Saimiri sciureus) in Parque Nacional del Manu, Peru, found that 21% of vocalizations were “caregiver” calls. Caregiver calls are brief, low frequency calls, often with numerous harmonics, that are addressed by caregivers to their own infants in three contexts: 1) prenurse, signalling the caregiver's location and willingness to nurse; 2) nurse, while nursing; and 3) end nurse, indicating the end of the nursing bout. Three measures (start, end, and peak frequency) of the acoustic structure of the fundamental frequency of the caregiver calls significantly differed across the contexts. Duration of caregiver calls, however, was not distinguished by context. Compared to other primate taxa, the specificity and importance of caregiver calls in squirrel monkey vocal behavior appears unusual, if not unique. That S. sciureus caregiver calls are highly developed and employed so extensively probably follows from an unusual combination of ecological and life history factors. These factors include delayed weaning and large infant body size, high levels of indirect foraging competition which encourages spatial separation, susceptibility to predation, and specialization on a densely foliated, branch-end microhabitat in which visual contact is often impeded. © 1995 Wiley-Liss, Inc.     

Chemotherapy of haemobartonellosis in squirrel monkeys (Saimiri sciureus)

Splenectomised Saimiri sciureus squirrel monkeys are being used increasingly as an experimental host for human malarial studies, notably for the assessment of candidate vaccines against Plasmodium falciparum blood-stage infection. Recently, we have reported that colony-reared S. sciureus monkeys are asymptomatic carriers of Haemobartonella sp. and that patent Haemobartonella infection, activated following splenectomy, may interfere with the course of P. falciparum parasitaemia in these animals. For several years, splenectomised S. sciureus monkeys were routinely submitted to oxytetracycline therapy before their use in malarial studies in order to prevent a possible spontaneous Heamobartonella infection. However, we report here that such antibiotic therapy is often ineffective and that neoarsphenamine chemotherapy may be considered as an alternative to cure both latent and patent haemobartonellosis in S. sciureus monkeys.     

Axial skeleton of Cebupithecia sarmientoi (Pitheciinae,Platyrrhini) from the middle miocene of La Venta,Colombia

The axial skeleton of Cebupithecia sarmientoi is described and analyzed for its functional and phylogenetic implications. The vertebrae of the holotype of C. sarmientoi (UCMP 38762) most closely resemble those of the extant pitheciine genus Pithecia and display features associated with adaptations for clinging and leaping as in that genus. Cebupithecia has a relatively long non-prehensile tail, which is most similar in absolute dimensions and proportions to Pithecia monachus. It also shares with P. monachus a distinctive morphology of the thoracic vertebrae, specifically the presence of a bony pillar spanning the vertebral lamina and body, caudal to the pedicle, herein designated the vinculum laminum. It is proposed that many of these features are shared primitive retentions from the last common ancestor of the Cebupithecia-pitheciine clade.