Factors influencing weight changes in callitrichids at the Bronx Zoo.

Callitrichids are small monkeys with high metabolic rates who appear to be susceptible to spontaneous diseases and possibly to environmental changes creating challenges in maintaining them in captivity. This study investigates whether life events (i.e. medical, social and housing changes) can influence weight. In previous research, body mass has been shown to be correlated with periods of illness, group composition changes and stress. Weights of 56 individual callitrichid monkeys (20 marmosets, 26 tamarins and 11 lion tamarins) at the WCS's Bronx Zoo were examined over approximately 2½ years. Weight fluctuations were scored based on 5%, 10% and 1 standard deviation criteria during periods of medical (illness and injury), social (introductions and separations), housing (movement within or between buildings) events and during periods when no-events occurred. Additionally, weights were examined for 3 months before and after periods of illness to look for trends in weight changes for 47 medical events (14 marmosets, 21 tamarins and 12 lion tamarins). Moreover, in five alloparenting males (four tamarins and one lion tamarin), weights were examined to determine if weight loss occurred after births as observed in earlier studies. The results show that a 5% and 1SD criterion may be too sensitive a criterion. We therefore deemed that a 10% weight loss may be the best criterion. For marmosets, a 10% weight loss occurred in association with all events. For tamarins, weight loss occurred with housing events. In lion tamarins, weight loss was observed with medical events. No significant weight loss was observed in alloparenting males.

Modeling reciprocation and cooperation in primates: evidence for a punishing strategy.

Experiments in which animals strategically interact with one another or search over some controlled domain are becoming common. While these experiments often promise to illuminate sophisticated animal behavior, the analyses brought to bear on these data are often quite coarse. For example, many papers simply tally the number of observations consistent with a behavioral theory. This analysis is simple, but ignores a potentially rich source of information by failing to take into account patterns and systematic variation among observations inconsistent with the theory. Using a new data set generated by cotton-top tamarin monkeys playing a repeated food-exchange game, we apply a maximum-likelihood estimation technique (more commonly used to study human economic behavior) which utilizes much more of the information in these data, and which uncovers unexpectedly sophisticated cooperative behavior from our subjects. Tamarin cooperation remains stable as long as both actors consistently cooperate, but requires at least two consecutive unexpected acts of cooperation to restart cooperation after it has collapsed, a strategy that resembles two-tits for a tat. We conclude by enumerating the benefits of a maximum-likelihood approach in experimental settings such as ours, and suggest other areas in which these techniques may be fruitful.

Response to novel objects and foraging tasks by common marmoset (Callithrix jacchus) female pairs.

The authors analyze the effects of enrichment devices on the behavior of common marmoset female pairs, and determine which aspects of these devices are more likely to elicit explorative behaviors, and how their presence affects aggressive and stress-related behaviors. The results support the use of enrichment devices for captive primates and show that in marmosets, their effectiveness strongly depends on location within the enclosure and the presence of hidden food.

Cone pigment variations in four genera of new world monkeys.

Previous research revealed significant individual variations in opsin genes and cone photopigments in several species of platyrrhine (New World) monkeys and showed that these in turn can yield significant variations in color vision. To extend the understanding of the nature of color vision in New World monkeys, electroretinogram flicker photometry was used to obtain spectral sensitivity measurements from representatives of four platyrrhine genera (Cebus, Leontopithecus, Saguinus, Pithecia). Animals from each genus were found to be polymorphic for middle to long-wavelength (M/L) sensitive cones. The presence of a short-wavelength sensitive photopigment was established as well so these animals conform to the earlier pattern in predicting that all male monkeys are dichromats while, depending on their opsin gene array, individual females can be either dichromatic or trichromatic. Across subjects a total of five different M/L cone pigments were inferred with a subset of three of these present in each species.

Multiple environmental contexts and communication in pygmy marmosets (Cebuella pygmaea).

There are multiple components to the concept of Umwelt experienced by an organism that may constrain the type and structure of communication signals as well as the usefulness of these signals. To illustrate the impact of these multiple environmental components, the authors used signals of the pygmy marmoset (Cebuella pygmaea), a small primate from the western Amazon. The authors summarize studies to show how the physical effects of the habitat; effects of other species, both predators and nonpredators; anthropogenic effects on the communication environment; within-group and between-groups influences other pygmy marmosets exert; and ontogeny influence the structure and usage of vocal signals. Communication within a species can be understood only in consideration of each of these contexts.

Food sharing in black lion tamarins (Leontopithecus chrysopygus).

Food sharing behavior was investigated by studying 10 captive black lion tamarin (Leontopithecus chrysopygus) infants (six litters) between the ages of four and 26 weeks. The frequency of sharing by parents in response to infant begging increased steadily from the age of five to nine weeks, but then declined gradually, although infants were still receiving food even at 26 weeks. Until the age of 15 weeks, infants received more food items by transfer from other group members than they did from self-feeding. Thereafter, self-feeding predominated. Offering of food by adults without prior infant begging occurred at low frequencies (5.3% of items transferred) and ceased at 20 weeks of age. Begging success (the proportion of infant begs which resulted in food sharing) remained relatively constant, averaging 65%. In common with other lion tamarins, black lion tamarins appear to continue to share food with infants well after weaning, and until at least six months of age.

The behavioural ecology of mixed-species troops of callitrichine primates.

This review summarizes information on the behavioural ecology of mixed-species troops (interspecific associations) formed by different species of callitrichines, small New World monkeys, in western and central Amazonia. The formation of mixed-species troops is an integral part of the biology of several species of this subfamily. Niche separation between associated species is obtained through vertical segregation which results in differences in the prey spectrum. The degree of niche separation is a predictor for the stability of mixed-species troops. Individuals may benefit from the formation of mixed-species troops through increased safety from predators, increased foraging efficiency, and/or increased resource defence. Costs of mixed-species troop formation are probably very low and mainly relate to patterns of interspecific behavioural interactions. We point to gaps in our knowledge and suggest pathways for future research into mixed-species troops.

Biological propensities of the Callitrichinae: a much used-little known group.

The use of callitrichid primates in biomedical research was encouraged initially by their susceptibility to various diseases such as infectious hepatitis and rubella. However, there was no supporting biological knowledge which helped to keep them healthy and breed effectively in captivity. Further, various callitrichid biomedical models are endangered species; hence, animal welfare and primate conservation are interrelated. Recent information has extended our knowledge of the natural life styles of these species in various ways; but there is still little to predict persistent concerns of effective management in captivity. Hence, we need practical information such as those derived from laboratory records of housing, reproduction, diet and health, together with studies that compare specifically behaviour in different laboratory conditions. More important in the long run, is that we study the biobehavioural propensities of different species. As yet callitrichids are largely unknown in these regards--a situation that continues to present problems for the reliability, validity, standardization and generalization of experimental procedures.

Relation between food preference and food-elicited vocalizations in golden lion tamarins (Leontopithecus rosalia).

We report the results of 2 studies on food-elicited vocalizations in golden lion tamarins (Leontopithecus rosalia). First, we investigated the preferences of 10 golden lion tamarins for 6 foods. Tamarins prefer mealworms and raisins significantly more than apple, egg, carrot, or marmoset diet. Food preference rank was significantly and positively correlated with the rank of latency to choose a particular food. Second, we investigated the relation between food preference and 15 vocal parameters measured from the calls emitted by 5 tamarins to a subset of the foods. Only 1 parameter was significantly correlated with food preference across animals. Within-subjects multivariate analysis of variance showed that the vocalizations to foods are significantly different. Our results support an hypothesis that food-elicited vocalizations vary in ways that correspond to the caller's preference but not in a manner that labels food type.

Maternal differences in infant carriage in golden-headed lion tamarins (Leontopithecus chrysomelas).

Infant-carrying behaviour was observed in two families of captive golden-headed lion tamarins. Although the young were raised in almost identical social situations, we found a reversed involvement of mother-father pairs in the amount of time they carried their offspring. In one case, the parental division of carrying behaviour was consistent with the standard description for callitrichids in that the adult male was the primary carrier. In the other family, the mother carried the infant considerably more than the male. Comparison of transfer initiations and transfer times showed that maternal choice operated. It is suggested that maternal behavior may depend primarily on the female's physical and hormonal condition.

Patterns of social preference across different social contexts in golden lion tamarins (Leontopithecus rosalia).

We investigated the role of mutual and circumstantial factors in maintaining exclusive social relationships in a New World primate. Four breeding pairs of golden lion tamarins (Leontopithecus rosalia rosalia) were allowed to interact with their mate or an unfamiliar, opposite-sex adult in each of 4 different social contexts: in view of the mate, out of the mate's view, with only the mate present, and with only the unfamiliar animal present. Males and females were in proximity to, approached, and sniffed their mates significantly more often than they did unfamiliar tamarins. These behaviors suggest a preference for the familiar mate. However, when mates were absent, tamarins demonstrated significantly higher levels of approach and sniffs toward unfamiliar animals. These patterns of behavior indicate that circumstantial factors, such as social context, may regulate social interactions between paired tamarins and unfamiliar, opposite-sex conspecifics.

Food-sharing in cotton-top tamarins (Saguinus oedipus).

Food-sharing behaviour was observed in 9 captive families of cotton-top tamarins (range 4-14 individuals per group), during meals of fresh fruit. Food was transferred to infants by their parents and older sibs in response to begging, and was also offered to them without prior solicitation. Older, mature, reproductively suppressed individuals shared more than young immature monkeys. Infants in larger families received more food than those in smaller ones, though individuals in smaller families shared more. Transfer to infants increased to a maximum at 12 weeks of age and then declined gradually. At one year of age they no longer received food from others. Food sharing by older siblings is a form of helping behaviour which may increase their inclusive fitness, and benefit parents, both directly, by reducing the costs they incur in rearing young, and indirectly, by increasing the amount of food available to infants.