Callitrichid Species Research Articles

Callitrichid responses to dead and dying infants: the effects of paternal bonding and cause of death.

Many primates show responses to dead infants, yet testing explanations for these behaviors has been difficult. Callitrichids present a unique opportunity to delineate between hypotheses, since unlike most species, male caretakers form closer social bonds with infants than mothers. Callitrichids are also known to commit infanticide, leaving obvious wounds that may enable them to more readily recognize death. We present: (1) a case study of a wild common marmoset (Callithrix jacchus) group responding to an infant's natural death, and (2) a review of published infant deaths across callitrichids (N = 16), testing for trends in the sex of reacting individuals and cause of death. In our case study, several group members frequently interacted with the dead infant, attempting to carry it. However, the strongest response was from a male that remained with the corpse for ~ 3h, despite his group leaving the area. Across callitrichid species, corpse interactions were significantly sex-biased: 100% (N = 6) of accidental deaths involved corpse interaction by males (p = 0.007), compared to 60% (N = 3 of 5) by females (p = 0.095). Cause of death also played a significant role, with individuals attempting to carry dead infants in 100% (N = 6) of accidental deaths, but only 11.1% (N = 1 of 9) of infanticides (p = 0.001). Although the available literature is small and potentially subject to publication biases, these data support the idea that visually obvious wounds may influence callitrichids' perception of dead conspecifics. Additionally, male-biased patterns of corpse interaction in callitrichids indicate that social bonds likely shape reactions to the dead, in addition to kinship. While published data on primate thanatology are limited, this study demonstrates quantitative approaches that can provide empirical insights into primates' responses to dead conspecifics.

Intraspecific and intrafamilial variation in primate forearm muscle architecture

Recent studies have examined locomotion and postural correlates of primate forearm muscle architecture. However, these have done so using relatively small sample sizes – usually one or two specimens per species, and relatively few species per genus and family. Thus, little is known about intraspecific variation in forearm muscle fiber architecture in primates, and whether there are notable differences in these variables between closely related taxa. The current study addresses these deficits by assessing both qualitative (presence/absence of specific muscles) and quantitative (physiological cross‐sectional area [PCSA], fascicle length [FL] and muscle mass [MM]) differences in forearm muscle architecture of larger intraspecific and samples with greater coverage of specific primate families than had been included in previous work. Namely, we studied 30 callitrichid specimens from 11 species, 15 lemurid specimens from 7 species and 9 cebids from two species ‐ a total sample size of 54 specimens from 20 species. Within species, FL varied the greatest among architectural variables and MM varied the least. We also found that there is great variation in both the extent of separation and fusion of flexor digitorum superficialis and profundus, and in the extent of accessory extensors in most species of callitrichids and Saimiri, but no variation in the gross forearm muscle architecture within lemurids. More than a quarter of the callitrichid specimens had forearm muscle configurations that deviate from their standard published description, suggesting that blanket characterizations of anatomical configurations at the genus or family level may obscure potentially important intra‐ and inter‐specific trends.Support or Funding InformationNational Science Foundation: IOS‐15‐57125, BCS‐14‐40599

Inferential reasoning in the visual and auditory modalities by cotton-top tamarins (Saguinus oedipus).

Nonhuman primate species appear to vary markedly in inferential reasoning abilities as measured by a classic inference-by-exclusion cup task. Even within species, individuals who can solve the cup task in the visual domain often struggle to use analogous auditory cues. Here we tested five cotton-top tamarins (Saguinus oedipus), cooperatively breeding New World monkeys that use both visual and auditory information when foraging, to investigate whether they might be able to solve the inference-by-exclusion task in both domains. Four subjects completed the testing series in both domains. Although three subjects performed well in the visual task, only one subject chose food location significantly above chance in response to positive auditory cues. These results demonstrate the first evidence of inferential reasoning abilities in a callitrichid species, while also revealing the performance asymmetry between the visual and auditory modalities observed in many other primates. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Identification of possible nutritional and stress risk factors in the development of marmoset wasting syndrome.

Marmoset wasting syndrome (MWS) describes a series of symptoms in callitrichids that lead to general weakness and a failure to thrive in captive conditions such as zoological institutions. Though the cause of MWS has not been identified, the majority of hypotheses are linked to deficiencies of specific nutrients and increased stress levels. Questionnaires were sent to zoos requesting information on diets and housing of currently living and dead callitrichids before their deaths, as well as their postmortem reports. Risk factors for development and occurrence of MWS include close proximity of predator enclosures and high levels of dietary magnesium and zinc. Variables with effects which may protect against the development of MWS included provision of a nest box, natural trees within enclosure, reduced visibility to visitors, as well as dietary factors such as higher concentrations of potassium and fiber fractions. The protective effects of limited concentrate feeds and increased total dietary fiber may help reduce the risks of developing MWS. The minerals may not have biological implications in MWS per se, however, they may be reflective of diets too high in concentrates and too low in plant matter. Habitat designs that are less naturalistic and those which provide insufficient privacy or hide areas may increase chronic stress for callitrichid species, possibly because of visitor-related stress. Other causes of chronic stress in captive zoo populations should be the topic of further research to reduce occurrence of MWS.

Multi-male groups positively linked to infant survival and growth in a cooperatively breeding primate

Cooperative breeding is a system where helper individuals care for breeding individuals’ offspring. As a result, social environment is likely to play a key role in regulating reproductive success. In primates, cooperative breeding is only found in the family Callitrichidae. Callitrichid males typically provide more infant care than non-breeding females, and in many callitrichid species, the presence of multiple males has been linked to infant survival. Leontopithecus chrysomelas (the golden-headed lion tamarin) is an endangered callitrichid found in the Atlantic Forest of Brazil. We used long-term data for wild L. chrysomelas to assess the influence of social group composition on reproductive success. Our survival model found that infant survival was negatively associated with group size, but this cost was mitigated by the presence of multiple adult males vs a single adult male. We also found that infants raised in groups with multiple adult males exhibited faster growth rates and higher adult weights than infants raised with a single adult male. This study adds novel evidence for the positive influence of adult males on callitrichid reproduction, demonstrating that adult males influence infant growth, as well as survival, in wild populations of cooperatively breeding primates. We suggest that social group composition, particularly the presence of adult males, be considered in future conservation strategies given its importance for reproductive success. In cooperatively breeding species, group members care for breeding individuals’ offspring. Due to this care, group composition may have a strong influence on infant success. In cooperatively breeding primates, males often provide more infant care than females. We investigated the influence of group composition on infant success in a cooperatively breeding primate, the golden-headed lion tamarin. Using long-term field data, we found that infant survival decreased as group size increased. However, this effect was reduced when multiple adult males were present in the group compared to a single male. We also found that infants grew faster and reached larger adult weights in the presence of multiple adult males compared to a single male. Our results demonstrate the importance of group composition for cooperative breeders and provide new evidence for the positive influence of adult males on cooperatively breeding primate infants.

Environmental complexity and feeding enrichment can mitigate effects of space constraints in captive callitrichids.

Non-human primates housed in zoos and laboratories often exhibit reduced activity and this poses welfare concerns. We examined the effects of enclosure types of differing size and environmental complexity on the activities of two species of callitrichids. We found that cotton-top tamarins housed in an enclosure of larger size and more environmental complexity showed higher activity levels, which was mainly contributed by more feeding/foraging activity. By contrast, Goeldi's monkeys housed in an enclosure of larger size and more environmental complexity showed lower activity levels, which was mainly contributed by less locomotory activity. In both species, off-exhibit groups housed in smaller enclosures did not show significantly less locomotory activity which would have been expected, as larger availability spaces should allow more opportunities for locomotion. Furthermore, the feeding enrichment had significant effects on increased feeding/foraging activity for both cotton-top tamarins and Goeldi's monkeys, irrespective of enclosure type. These results suggested that environmental complexity (or application of feeding enrichment) that provided more opportunities for natural foraging could have a larger effect on overall activity levels compared with larger enclosure sizes that should provide more locomotion opportunities. More importantly, it showed that even when enclosure space and complexity were limited, increased opportunities for foraging through the application of enrichment could increase species-typical behaviours. Such inexpensive, easy to implement enrichment methods should be applied to provide more complex environments for captive non-human primates, particularly in situations where there are logistical and/or cost constraints to the modification of physical exhibits.

An investigation of ecological correlates with hand and foot morphology in callitrichid primates

Studies of primate taxonomy and phylogeny often depend on comparisons of limb dimensions, yet there is little information on how morphology correlates and contributes to foraging strategies and ecology. Callitrichid primates are ideal for comparative studies as they exhibit a range of body size, limb proportions and diet. Many callitrichid species exhibit a high degree of exudativory, and to efficiently exploit these resources, they are assumed to have evolved morphologies that reflect a level of dependence on these resources. We tested assumptions by considering measurements of limb proportion and frictional features of the volar surfaces in preserved specimens of 25 species with relation to published life history and ecological data. The degree of exudativory and utilization of vertical substrates during foraging were found to correlate both with size and with size-corrected foot and hand dimensions. Smaller species, which engage in greater degrees of exudativory, had proportionally longer hands and feet and more curved claw-like tegulae (nails) on their digits to facilitate climbing on vertical substrates. The density of patterned ridges (dermatoglyphs) on the volar surfaces of the hands and feet is higher in more exudativorous genera, suggesting a role in climbing on vertical tree trunks during foraging. Dermatoglyph comparisons suggest that ridges on the soles and palms may facilitate food procurement by enhancing frictional grip during exudate feeding. Volar pad features corroborate taxonomic relationships described from dental morphology.

Alarm Calls of Marmosets (Callithrix geoffroyi) to Snakes and Perched Raptors

Communication about the presence of predators is an important benefit of group living. Critical information about the nature of danger can be conveyed through referential alarm calls. Raptors pose a significant predatory threat to callitrichid species. Unlike a raptor in flight, a perched raptor cannot attack suddenly at great speed, and it can be monitored from a safe distance. In this sense a perched bird may pose a threat more similar to that of a terrestrial predator such as a snake. Here we compare predatory contexts by addressing these two questions: 1) Do marmosets produce acoustically distinct alarm calls to snake models and perched raptor models? 2) Do the visual responses of the marmosets to the playbacks of perched raptor–elicited calls differ from those given to the playbacks of calls given in response to snakes? We recorded alarm calls from two groups of outdoor-housed Geoffroy’s marmosets (Callithrix geoffroyi) in response to predator models. Later, we played back stimuli created from these recordings to the marmosets and scored their gaze direction. Results show that calls given to models of perched raptors are acoustically distinct from those given to models of snakes. Further, the relative number of upward to downward looks while listening to the playbacks of perched raptor–elicited calls was significantly greater than it was for snake-elicited calls. Reactions to airborne raptors are known to elicit freezing or rapid flight, neither of which occurred in response to our playbacks. Our data suggest a greater complexity in the alarm call repertoire of marmosets than previously demonstrated.

EVOLUTION OF ASPM IS ASSOCIATED WITH BOTH INCREASES AND DECREASES IN BRAIN SIZE IN PRIMATES

A fundamental trend during primate evolution has been the expansion of brain size. However, this trend was reversed in the Callitrichidae (marmosets and tamarins), which have secondarily evolved smaller brains associated with a reduction in body size. The recent pursuit of the genetic basis of brain size evolution has largely focused on episodes of brain expansion, but new insights may be gained by investigating episodes of brain size reduction. Previous results suggest two genes (ASPM and CDK5RAP2) associated with microcephaly, a human neurodevelopmental disorder, may have an evolutionary function in primate brain expansion. Here we use new sequences encoding key functional domains from 12 species of callitrichids to show that positive selection has acted on ASPM across callitrichid evolution and the rate of ASPM evolution is significantly negatively correlated with callitrichid brain size, whereas the evolution of CDK5RAP2 shows no correlation with brain size. Our findings strongly suggest that ASPM has a previously unsuspected role in the evolution of small brains in primates. ASPM is therefore intimately linked to both evolutionary increases and decreases in brain size in anthropoids and is a key target for natural selection acting on brain size.

Progressive parenting behavior in wild golden lion tamarins

Young primates in the family Callitrichidae (the marmosets and tamarins) receive extensive and relatively prolonged care from adults. Of particular note, callitrichid young are routinely provisioned until well after weaning by parents and helpers, which is in stark contrast to typical juvenile primates, who must acquire most of their food independently once they are weaned. Adults of some callitrichid species produce a specialized vocalization that encourages immature group members to take proffered food from the caller. Here, I report that wild adult golden lion tamarins (Leontopithecus rosalia) not only used this food-offering call to encourage young, mobile offspring to approach and take captured prey from them, but as the young began to spend significant time foraging for themselves and to acquire prey by independent means, the frequency of these vocalizations in the context of food transfer declined. Adults then began to use food-offering calls in a novel context: to direct juveniles to foraging sites that contained hidden prey that the adults had found but not captured. During the period of these most frequent adult-directed prey captures, the independent prey-capture success rates of juveniles improved. Thus, adults modified their provisioning behavior in a progressive developmentally sensitive manner that may have facilitated learning how to find food. I hypothesize that as a result of these demonstrations by adults, juveniles either may be encouraged to continue foraging despite low return rates or to learn the properties of productive prey-foraging substrates in a complex environment.

Feeding ecology of a group of buffy‐headed marmosets (Callithrix flaviceps): fungi as a preferred resource

Mycophagy is a relatively rare behavior in primates and has only been recorded in five callitrichid species. Here, we present data on the feeding ecology of a free-ranging group of Callithrix flaviceps, which was studied in the Augusto Ruschi Biological Reserve, Southeastern Brazil, in 2008. In contrast with other marmosets, which are typically gummivorous, the study group was predominantly mycophagous-insectivorous, with fungi corresponding to 64.8% of total feeding records, and gum (6.1%) and fruit (3.3%) together providing only a minor part of the diet. Prey corresponded to 25.8% of the group's diet. The fungi (Mycocitrus spp.) consumed by the marmosets were found attached to the stems of Merostachys bamboo. As the animal component of the group's diet was similar to that recorded in studies of other marmosets, we propose that fungi were exploited primarily as a substitute for plant material, in particular exudates. This highly mycophagous diet may be determined by two principal factors: (1) the abundance of fungi within the study area, and (2) the avoidance of bark gouging, for which C. flaviceps may be less specialized than most other marmosets. These conclusions are supported by comparisons with other marmoset groups, which indicate an ecological specialization for mycophagy in C. flaviceps, and that the species will resort to gummivory in habitats where fungi are scarce.

Reconciliation in captive cotton‐top tamarins (Saguinus oedipus), a cooperative breeding primate

Reconciliation has been demonstrated in all primate species in which the phenomenon has been studied. However, reconciliation has been studied in only two species of callitrichids, and conclusions remain controversial. The first aim of this study has been to find out whether captive cotton-top tamarins (Saguinus oedipus) reconcile, since this is the first such study on this species. We examined 227 conflicts in three family groups (N=19). Instances in which individuals remained together in t=0 (29; 12.8%) were not analyzed. The cotton-top tamarins showed heightened affiliation between opponents in the postconflict periods (PC) compared with matched control (MC) periods (39.88+/-5.12% and 3.18+/-1.27%, respectively), with a corrected conciliatory tendency of 37.17+/-5.37%, and a "time window" that included the first 180 sec of the PC period. Former opponents were the most likely recipient of affiliative behaviors during the PC periods: 39.83+/-4.26% vs. 11.36+/-5.33% during MC periods. The proportion of attracted pairs (47.13+/-6.25%) was significantly higher than those of dispersed pairs for male-male conflicts (3.79+/-1.79), but not for male-female conflicts (27.31+/-9.32 and 4.82+/-2.9, respectively). In cooperative-breeding species, specific sex-class dyads might differ in how they resolve conflicts.

Hematologic iron analyte values as an indicator of hepatic hemosiderosis in callitrichidae

Hepatic hemosiderosis is one of the most common postmortem findings in captive callitrichid species. Noninvasive evaluation of hematologic iron analytes has been used to diagnose hepatic iron storage disease in humans, lemurs, and bats. This study evaluated the relationship between hematologic iron analyte values (iron, ferritin, total iron binding capacity, and percent transferrin saturation) and hepatic hemosiderosis in callitrichids at the Wildlife Conservation Society's Central Park and Bronx Zoos. Results revealed that both ferritin and percent transferrin saturation levels had strong positive correlations with hepatic iron concentration (P<0.001, r=0.77, n=20; P<0.001, r=0.85, n=10, respectively). Serum iron levels positively correlated with hepatic iron concentration (P=0.06, r=0.56, n=11), but this finding was not significant. Serum total iron binding capacity did not significantly correlate with hepatic iron concentration (P=0.47, r=0.25, n=10). Both ferritin and hepatic iron concentration positively correlated with severity of hepatic iron deposition on histology (P<0.05, r=0.49, n=21; P<0.001, r=0.67, n=21, respectively). This study suggests that ferritin, serum iron concentration, and percent transferrin saturation are convenient, noninvasive, antemortem methods for assessing severity of hemosiderosis in callitrichids.

Vocal Response of Captive-reared Saguinus oedipus During Mobbing

Mobbing is an important component of antipredator behavior for animals from many taxa. Callitrichids are small-bodied primates that mob multiple types of predators. Though there have been several observations of callitrichids mobbing predators in the wild, their anecdotal nature provides only rough descriptions of behavior and vocalizations. Researchers could neither spectrographically identify nor quantify vocalizations owing to the limitations of observing predation in the field. We examined in detail the mobbing response of 1 callitrichid species, the cotton-top tamarin, in captivity. We recorded vocalizations for quantitative analysis and observed behavior qualitatively. We report 3 new vocalizations that had not been described in the original repertoire for the cotton-top tamarin. Analysis of the time course of a mobbing session yielded a pattern in which the highest intensity mobbing vocalizations decreased over the session even though lower intensity vocalizing continued, which may reflect a shifting strategy from mobbing to vigilance. The rate of calling during mobbing sessions differed from the rate of calling during control sessions. We discuss the vocalizations in relation to 2 hypotheses of form and function of antipredator calls. The newly described mobbing vocalizations may have an important impact on the study of mobbing because they represent a class of vocalizations that researchers have largely ignored in studies of callitrichids, thus raising new issues concerning past and future research on antipredator behavior in the family.

Paracellular nutrient absorption in a gum‐feeding new world primate, the common marmoset Callithrix jacchus

The common marmoset is one of the few callitrichid species that is not threatened or endangered in the wild, and is widely used in biomedical research, yet relatively little is understood about its digestive physiology. Dietary specialization on plant exudates has lead to relatively reduced small intestines, yet the common marmoset has exceptional dietary breadth, allowing it to successfully utilize a variety of habitats. We predicted that passive, paracellular nutrient absorption would be used by the common marmoset to a greater extent than in other non-flying mammals. We measured the bioavailability and rates of absorption of two metabolically inert carbohydrates not transported by mediated pathways (L-rhamnose and cellobiose, molecular masses of 164 and 342, respectively) to measure paracellular uptake, and of a non-metabolized D-glucose analog (3-O-methyl-D-glucose) to measure total uptake by both mediated and paracellular pathways. We found high bioavailability of 3-O-methyl-D-glucose (83+/-5%), and much higher bioavailability of the paracellular probes than in similarly sized non-flying mammals (30+/-3% and 19+/-2% for L-rhamnose and cellobiose, respectively). Passive, paracellular nutrient absorption accounts for around 30% of total glucose absorption in common marmosets and intestinal permeability is significantly higher than in humans, the only other species of primate measured to date. This may allow the common marmoset to maintain high digestive efficiency when feeding on higher quality foods (fruit, arthropods, gums with higher proportions of simple sugars), in spite of relatively reduced small intestines correlated with adaptations for fermentative digestion of plant gums. We find no evidence to support, in primates, the hypothesis that reliance on paracellular nutrient absorption should increase with body size in mammals, but suggest instead that it may be associated with small body size and/or taxon-specific adaptations to diet.

EVALUATION OF CONTROL AND TREATMENT OF GONGYLONEMA SPP. INFECTIONS IN CALLITRICHIDS

Numerous cases of Gongylonema spp. infection with associated pathological lesions and clinical signs were identified in a collection of Goeldi's monkeys (Callimico goeldii) (GMs) at a zoological park during a 3-yr period. An increase in the incidence of clinical signs in the GMs and other callitrichid species prompted an investigation to determine the prevalence of infection within the collection and evaluate treatment protocols. Twenty-one callitrichids [nine GMs, four golden lion tamarins (Leontopithecus rosalia), six cotton-top tamarins (Saguinus oedipus), and two golden-headed lion tamarins (Leontopithecus chrysomelas)] were included in this study. Many of the animals had been positively diagnosed on past examinations. Repeated cytological evaluations of scrapings taken from the mucosa of the tongue were performed to diagnose infection. The animals were randomly divided into two groups and treated with either ivermectin (290 microg/kg p.o., q7 days for four doses) or mebendazole (70 mg/kg p.o. q24 hr for three doses). Follow-up scrapings were performed on all animals at days 35, 64, and 156. Numerous animals displayed clinical signs (facial pruritus, inflammation, and ptyalism) before and throughout the investigation; however, Gongylonema spp. infections were only confirmed by tongue scrapings in two animals. Fecal floatation by using a sodium nitrate solution for recovery of spirurid eggs also was performed, but it yielded no positive results. The low number of confirmed cases precluded comparative evaluation of the efficacy of the anthelmintic treatment protocols. However, both regimes seemed subjectively similar in decreasing clinical signs and were safe with no adverse effects. Diagnosis of Gongylonema spp. infection is challenging, even when severe clinical signs are present. This investigation further demonstrates the lack of a reliable ante-mortem test for the parasite and underscores the importance of treatment based on clinical signs. Until a more sensitive test is available, further comparison studies on treatment regimes will be difficult and likely unrewarding.

Demographic review of a captive colony of callitrichids (Callithrix kuhlii).

Although reports on colony demographics for a variety of callitrichid species are available in the literature, to date there has not been a detailed examination of Wied's black tufted-ear marmoset (Callithrix kuhlii). The purpose of this study is to present colony demographics for C. kuhlii from the University of Nebraska at Omaha's Callitrichid Research Center from 1991 to 2002. C. kuhlii are currently held in a number of zoological parks in the United States and abroad; however, the University of Nebraska at Omaha held the only breeding colony in North America. Here we report data on lifespan, sex ratio, litter size, and interbirth interval (IBI) for that captive breeding colony.

Golden lion tamarin sleeping‐site use and pre‐retirement behavior during intense predation

Sleeping sites, their patterns of use, and cryptic pre-retirement behavior mitigate predation risk at sleeping sites and could influence prey fitness. We evaluated sleeping-site usage for 10 groups of golden lion tamarins (GLTs) from a population that recently suffered a substantial decline due to predation at sleeping sites. We recorded the average number of nights that groups spent at their different sleeping sites to determine whether patterns of sleeping-site use were influenced by predation risk, as measured by the rate of encounters with predators, or the availability of suitable sleeping sites, as measured by the size of a group's home range and amount of mature forest within their home range. In addition, we measured travel speed to sleeping sites and compared this speed with that recorded at other times of day. GLT groups spent more nights on average at each of their sleeping sites compared to other callitrichid species for which data are available. Predation risk and habitat characteristics were not significant predictors of how many times groups used each of their different sleeping sites. Groups significantly increased their travel speed just before entering the sleeping site. Rapid locomotion to secure tree cavities may help GLTs avoid crepuscular and nocturnal predators; however, we speculate that this strategy failed numerous GLTs in our study population during the previous decade because they used sleeping sites that were accessible to predators.

Neophilia, innovation and social learning: a study of intergeneric differences in callitrichid monkeys

In a comparative study of neophilia, innovation and social attentiveness we exposed individuals in seven callitrichid species, from three genera, to novel extractive foraging tasks. The results revealed consistently shorter response latencies, higher levels of successful and unsuccessful manipulation, and greater attentiveness to the task and to conspecifics inLeontopithecus (lion tamarins) than in both Saguinus (tamarins) and Callithrix (marmosets). This is consistent with the hypothesis that species dependent upon manipulative and explorative foraging tend to be less neophobic and more innovative than other species. Furthermore, Callithrix appeared to be less neophobic than Saguinus; ifCallithrix is regarded as the greater specialist, this result is inconsistent with the hypothesis that neophobia is associated with foraging specialization. We consider the relevance of our findings to taxonomic relationships, and to technical and Machiavellian intelligence hypotheses and discuss the implications for captive breeding and reintroduction strategies.Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Feeding Gum Arabic to New World Monkeys: Species Differences and Palatability

AbstractMembers of the New World primate generaCallithrixandCebuellahave specialisations for eating plant exudates. Exudates are also an important component of the diets of many other callitrichid species in the wild, especially at times of nutritional stress. Gum arabic is fed daily to all marmosets and to some tamarins in Jersey Zoo's collection. This study investigated species differences in liking for gum and the effects of the concentration of gum solutions on palatability. As predicted from field data,Callithrixspecies consumed more gum than other species;Saguinusalso showed quite a strong liking for gum. In parallel with data from the wild, lion tamarins(Leontopithecusspp.) consumed the least, andCallimicoalso took relatively little. The two marmoset species tended to like stronger solutions of gum more than weak solutions and, therefore, the provision of smaller amounts of stronger concentrations is likely to be the most cost-effective way of incorporating gum into the diet. Providing gum to callitrichids on a regular basis can have significant welfare benefits.