Experimental American leishmaniasis in the Brazilian squirrel monkey (Saimiri sciureus): lesions, hematology, cellular, and humoral immune responses

Unulcerated cutaneous lesions appeared and persisted in squirrel monkeys experimentally infected with Leishmania braziliensis braziliensis or L. b. panamensis. Peripheral blood mononuclear cell (PBMC) numbers increased following infection, and cultured PBMCs from infected monkeys proliferated in response to parasite antigens. The responses of PBMCs to mitogens were not suppressed in infected monkeys. Elevated levels of leishmania-specific immunoglobulins M and G were also observed. Thus, the squirrel monkey is susceptible to American leishmaniasis and is capable of responding to the infection with measurable cellular and humoral immunity.     

Mycobacterium kansasii infection in squirrel monkeys (Saimiri sciureus sciureus)

Abstract: This report documents asymptomatic infections of Mycobacterium kansasii in four of five tuberculin positive squirrel monkeys (Saimiri sciureus sciureus). The mycobacterial DNA amplified by polymerase chain reaction (PCR) from a bronchial lymph node had no affinity for the species specific probes of M. tuberculosis, M. avium, and M. intracellular, thus allowing the presumptive diagnosis of an atypical mycobacterial infection. Infection by Mycobacterium kansasii was confirmed by culture of bronchial lymph nodes from three monkeys. The source of the infection was never identified.     

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.     

Food-storing behavior in captive squirrel monkeys (Saimiri sciureus)

Observations of food-storing in caged squirrel monkeys are described. Frequencies of storage and attempted retrievals increased with the introduction of novel objects. The type of storage site, its location and defense, all indicate hiding of food or favored objects to avoid stealing attempts rather than food or object play behavior.     

Reconciliation in captive Guyanese squirrel monkeys (Saimiri sciureus)

The tendency for agonistic interaction to increase the probability of friendly interaction between social partners has been demonstrated across a range of Old World primates. While research on such post-conflict behavior proceeds into an hypothesis-testing phase, new comparative information must accumulate to provide full phylogenetic perspective on primate social behavior. Data from New World and prosimian primates are yet extremely limited. We studied captive squirrel monkeys (Saimiri sciureus) via post-conflict (PC) and matched control (MC) observations and analyzed results using both the PC-MC and time-rule methods. Former opponents maintaining affiliative relationships soon engaged in friendly interaction following large proportions of agonistic interactions, whereas non-affiliated individuals, including virtually all male-female pairs, reconciled conflicts rarely. Close-proximity approaching and huddling contact constituted the principal modes of post-conflict amicability. Agonistic interactions of relatively high intensity were most likely to be reconciled and most likely to be reconciled via physical contact. High vulnerability of Saimiri to predation may have favored this species' strong inclination to reconcile soon after agonistic interaction. Research on free-living populations of this and other primate species is needed to illuminate similarities and differences across taxa.     

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.     

Captive breeding of squirrel monkeys,Saimiri sciureus and Saimiri boliviensis: The problem of hybrid groups

The electrophoretic variability of blood proteins coding for up to 32 genetic loci was analyzed in 108 squirrel monkeys (Saimiri sciureus, Saimiri boliviensis, hybrids) from two captive colonies. Twelve polymorphic loci with 31 alleles are reported. The biallelic Ada* locus, G-statistics and Hardy-Weinberg genotype equilibria are useful for recognizing hybrids between S. sciureus and S. boliviensis. Backcrosses in hybrid stocks and gene flow in a natural hybrid belt, however, complicate the taxonomic diagnosis of captive specimens: S. sciureus phenotypes imported from Peru possessed the allele Ada*132, which generally characterizes S. boliviensis (or species hybrids). The complex taxonomy of Saimiri spp. Requires careful planning of captive breeding. We suggest a genetic analysis of the founder individuals before their inclusion in the European studbook population and to breed S. sciureus from Guyana separately from Peruvian imports, because the latter bear a greater risk of being taxonomically heterogeneous. Zoo Biol 17:95–109, 1998. © 1998 Wiley-Liss, Inc.     

Social hierarchy under different criteria in groups of squirrel monkeys,Saimiri sciureus

Under different criteria the individual members of groups of squirrel monkeys show different social capacities. The ranking of the subjects was much the same for Restraining and Genital display. The hierarchies for Approaching and Following fitted well with each other, showing few similarities with the above two. Location of individual ranks for Withdrawing tended to be the opposite to that of Approaching and Following. Restraining and Genital display showed quasi-linear hierarchies, with males on top and females at the bottom of them. For Approaching, Following, Withdrawing, and Genital inspection the results varied from quasi-linear structure to circular or even unisexual arrangement. As a rule the animals behaved towards partners close in rank to themselves. Several individual roles could be isolated: An alpha male role, directing Restraining and Genital display to all other partners more frequently than any of them towards him, basing his ability more in adequate distribution of total performance among social partners than in high total frequency; an omega male role under the same criteria, whose function would be to connect with the hierarchy of females and a scapegoat role, a very passive female receiving all kinds of attention from most subjects.     

Age differences and developmental trends in alarm peep responses by squirrel monkeys (Saimiri sciureus)

Alarm calls can code for different classes of predators or different types of predatory threat. Acoustic information can also encode the urgency of threat through variations in acoustic features within specific alarm call types. Squirrel monkeys (Saimiri sciureus) produce an alarm call, known as the alarm peep, in highly threatening situations. Infant squirrel monkeys appear to have an innate predisposition to respond to alarm peeps but require experience to associate alarm peeps with the appropriate type of predatory threat [Herzog & Hopf, American Journal of Primatology 7:99-106, 1984]. Little is known about age-related differences in the type or frequency of response to alarm peeps, or the development of alarm peep response in infants. The purpose of this study was to test experimentally the response strategies of different age classes of squirrel monkey to the playback of alarm peeps that were produced by infants, juveniles, or adults. Results suggest that infants, juveniles, and female subadults respond more frequently to alarm peeps than do adult females. Infant squirrel monkeys showed different behavioral strategies in response to alarm peeps as a function of age. Adult females differentiate between infant and adult alarm peeps by responding more frequently to the alarm peeps of adult females. These data demonstrate that squirrel monkeys use acoustic information to discern when to respond to the alarm peeps from conspecifics, and that infants gradually develop an adult-like response to alarm peeps over the first year of development.     

Breeding and rearing squirrel monkeys (Saimiri sciureus) in captivity.

A breeding colony of squirrel monkeys (Saimiri sciureus) was established to provide animals for behavioral research concerned with early development. The origin of the initial breeders was Peru, Colombia, and Bolivia. During the past 10 years, the colony has grown to 125 adult females, 20 adult males, and 120 immature animals of various ages. The annual conception rate for the last 5 years averaged 68%. This resulted in 84% viable births of which 82% survived past 6 months of age. The majority of the births (65%) occurred during June-August, and 87% during May-September. The most efficient and successful breeding strategy was to form mixed-sexed groups of 10--15 females and 2--3 males before the mating season began and to maintain the integrity of these groups with minimal interference. Progeny were reared apart from their natural mother without difficulty, and their growth and development were found to be similar to those of mother-reared monkeys.     

Characterization of Gilbert-like syndrome in squirrel monkeys (Saimiri sciureus)

Bolivian squirrel monkeys, unlike those of Brazilian origin, exhibit a marked fasting hyperbilirubinemia (FH) similar to that observed in Gilbert's syndrome in man. Since no delays in the hepatic clearance of sulfobromophthalein or indocyanine green are present, the Bolivian monkey appears to be similar to Gilbert's type I syndrome. FH can be significantly decreased by either phenobarbital or tin-protoporphyrin pretreatment. Nicotinic acid-induced hyperbilirubinemia and delayed tolbutamide clearance were not observed as in the human syndrome.     

Clinical description of tetanus in squirrel monkeys (Saimiri sciureus).

Nineteen cases of clinical tetanus developed in Bolivian squirrel monkeys (Saimiri sciureus) which were housed in outdoor corrals with soil-based floors. The disease was initially characterized by stiffness in gait followed by extensor rigidity, trismus and opisthotonus. Eleven of the 19 monkeys (58%) had evidence of external wounds. The case fatality rate was 100%. Tetanus accounted for 12% of adult female and 19% of adult male mortalities in the colony. Immunization with tetanus toxoid was effective in reducing the incidence of tetanus.     

Social and reproductive behaviors in surrogate-reared squirrel monkeys (Saimiri sciureus).

A colony of 16 surrogate-reared squirrel monkeys was observed for the adequacy of social and reproductive behaviors at maturity. Aside from some self-directed abnormalities centering around nonnutritive orality, this group was behaviorally normal in spite of having no contacts with mother-reared, older conspecifics. Half (N=5) of the females gave birth, with four infants viable. One infant has remained with the colony and is thriving. The other three remained with the group for as long as 42 days before death or removal. Maternal care appeared adequate. Mean estimated conception age for females was 35 months, and the mean impregnation age for males was estimated to be 42 months.     

Conditions of observation and social distance in groups of squirrel monkeys,Saimiri sciureus

Observation conditions were very influential in determining the social distance among members of groups of squirrel monkeys. With observer visible to the animals and recording by talking into a tape recorder the monkeys did not show a consistent pattern of social distance as reflected by actual space and frequency of bodily contacts, whereas when the observer was concealed, looking through a one-way vision screen and recording silently by marking on paper, the subjects tended to group in unisexual clusters, with that of the females showing higher cohesiveness.     

Elevation in plasma glucagon levels in response to stress in squirrel monkeys: comparisons of two subspecies (Saimiri sciureus boliviensis and Saimiri sciureus sciureus)

Bolivian (Bo) and Brazilian (Br) squirrel monkeys (SMs) were captured and restrained to determine patterns of glucagon and glucose response. In both subspecies, plasma glucagon and glucose levels rose rapidly in response to restraint procedures; glucagon levels in BrSMs and glucose levels in both subspecies returned to basal values in 15 minutes. The magnitude of the glucagon and glucose responses differed significantly between BoSMs and BrSMs.     

Aneurysms in a large colony of squirrel monkeys (Saimiri sciureus)

This communication reports the findings of a retrospective study of extracranial aneurysms found at necropsy in a large colony of squirrel monkeys (Saimiri sciureus). Eleven (1.5%) of 730 cases had dissecting, saccular, or fusiform aneurysms of the carotid arteries or aorta. Saccular and fusiform aneurysms were found only in animals that had been fed atherogenic diets, whereas dissecting aneurysms occurred in both normo- and hypercholesterolemic monkeys. Neither the type or location of aneurysms, however, could be predicted by the length of time an animal consumed an atherogenic diet, nor by the total mean serum cholesterol concentration. The anatomical characteristics, location, and incidence of aneurysms found in squirrel monkeys resembled closely those observed in human autopsy cases.