Phylogenetic relationships of the callitrichinae (Platyrrhini,Primates) based on β2‐microglobulin DNA sequences

The phylogenetic relationships of callitrichine primates have been determined by DNA sequence analyses of exons 1, 2, and 3 of the β₂‐microglobulin gene. Parsimony, distance, and maximum likelihood analyses of ca. 900 base pairs of 21 taxa, representing all callitrichine genera, indicated that Saguinus was the most basal offshoot. Within Saguinus, S. fuscicollis appeared as the first divergent lineage followed by an unresolved trichotomy formed by S. mystax/S. imperator, S. midas/S. bicolor, and S. oedipus. A second callitrichine lineage was formed by Leontopithecus; each of the three species studied showed identical nucleotide sequences. Callimico appeared as the sister taxon of Callithrix/Cebuella. Genetic distances within this latter group were very small, although a stronger association between Cebuella and species of the Callithrix argentata group was observed. The inclusion of Cebuella in the genus Callithrix is suggested. These studies indicated that tamarins are more plesiomorphic than marmosets in agreement with the phyletic dwarfism hypothesis. Am. J. Primatol. 48:225–236, 1999. © 1999 Wiley‐Liss, Inc.     

Variable infant care contributions in cooperatively breeding groups of wild saddleback tamarins

Among non-human primates, alloparental infant care is most extensive in callitrichines, and is thought to be particularly costly for tamarins whose helpers may suffer increased energy expenditure, weight loss, and reduced feeding time and mobility. The costs and benefits of infant care likely vary among group members yet very few wild studies have investigated variable infant care contributions. We studied infant care over an 8-month period in four wild groups of saddleback tamarins in Bolivia to evaluate: (a) what forms of infant care are provided, by whom, and when, (b) how individuals adjust their behavior (activity, vigilance, height) while caring for infants, and (c) whether individuals differ in their infant care contributions. We found that infant carrying, food sharing, and grooming varied among groups, and immigrant males—those who joined the group after infants were conceived—participated less in infant care compared to resident males. Adult tamarins fed less, rested more, and increased vigilance while carrying infants. Although we did not detect changes in overall activity budgets between prepartum and postpartum periods, tamarins spent more time scanning their environments postpartum, potentially reflecting increased predation risk to both carriers and infants during this period. Our study provides the first quantitative data on the timing and amount of infant carrying, grooming, and food transfer contributed by all individuals within and among multiple wild groups, filling a critical knowledge gap about the factors affecting infant care, and highlighting evolutionary hypotheses for cooperative breeding in tamarins.     

Gum feeder as environmental enrichment for zoo marmosets and tamarins

Tamarins and marmosets are small-bodied social callitrichines. Wild callitrichines feed on exudates, such as sap and gum; particularly, marmosets are mainly gummivores, while tamarins consume gums only occasionally and opportunistically. Zoo marmosets and tamarins are usually provided with gum arabic as an alternative to the exudates normally found in the wild. The aim of this study was to evaluate the effects of a gum feeder on the behavior and well-being of four zoo-managed callitrichines. We studied four cotton-top tamarins (Saguinus oedipus), four red-handed tamarins (S. midas), two pygmy marmosets (Cebuella pygmaea), and three Geoffroy's marmosets (Callithrix geoffroyi) housed at Parco Natura Viva (Italy). We conducted the study over two different periods, a baseline (control, without the gum feeder) and then a gum feeder (when the gum feeder was provided) period. We used continuous focal animal sampling to collect behavioral data, including durations of social and individual behaviors. We collected 240 min of observations per period per study subject, with a total of 3,120 min for all the subjects in the same period and of 6,240 min in both periods. We analyzed data by using nonparametric statistical tests. First, we found that the gum feeder promoted species-specific behaviors, such as exploration, and diminished self-directed behaviors, suggesting an enriching effect on tamarin and marmoset behavior. Moreover, in red-handed tamarins, the provision of the gum feeder reduced the performance of self-directed and abnormal behavior, specifically coprophagy. These results confirm that gum feeders are effective foraging enrichment tools for zoo marmosets and tamarins.     

The functional morphology of the anterior masticatory apparatus in tree‐gouging marmosets (cebidae,primates)

Although all genera of Callitrichinae feed on tree exudates, marmosets (Callithrix and Cebuella) use specialized anterior teeth to gouge holes in trees and actively stimulate exudate flow. Behavioral studies demonstrate that marmosets use large jaw gapes but do not appear to generate large bite forces (relative to maximal ability) during gouging. Nonetheless, the anterior teeth of marmosets likely experience different loads during gouging compared to nongouging platyrrhines. We use histological data from sectioned teeth, μCTs of jaws and teeth, and in vitro tests of symphyseal strength to compare the anterior masticatory apparatus in Callithrix to nongouging tamarins (Saguinus) and other cebids. We test the hypotheses that (1) marmoset anterior teeth are adapted to accommodate relatively high stresses linked to dissipating gouging forces and (2) the mandibular symphysis does not provide increased load resistance ability compared with closely related nongouging platyrrhines. Differences in decussation between Callithrix and Saguinus are greatest in the anterior teeth, suggesting an increased load resistance ability specifically in incisor and canine enamel of Callithrix. Callithrix lower incisor crowns are labiolingually thicker suggesting increased bending resistance in this plane and improved wedging ability compared with Saguinus. Anterior tooth roots are larger relative to symphyseal bone volume in Callithrix. Anterior tooth root surface areas also are larger in marmosets for their symphyseal volume, but it remains unclear whether this relative increase is an adaptation for dissipating dental stresses versus a growth‐related byproduct of relatively elongated incisors. Finally, simulated jaw loading suggests a reduced ability to withstand external forces in the Callithrix symphysis. The contrast between increased load resistance ability in the anterior dentition versus relatively reduced symphyseal strength (1) suggests a complex loading environment during gouging, (2) highlights the possibility of distinct loading patterns in the anterior teeth versus the symphysis, and (3) points to a potential mosaic pattern of dentofacial adaptations to tree gouging. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.