Mustached tamarins prefer dry, upland forests in the Amazonian lowland and avoid flooded forests. (Fleagle, 1999)
Mustached tamarins, being callitrichines, have distinguishing features that set them apart from other New World monkeys. These include their diminutive body size and the presence of claw-like nails on all digits except the hallux. Mustached tamarins have also lost both their upper and lower 3rd molars and the hypocones on their upper molars. The dental formula is 2.1.3.2 / 2.1.3.2. Tamarins have spatulate incisors that are shorter than their canines, unlike marmosets which have incisors and canines of more similar size. The labial and lingual sides of their incisors are also thickened with enamel. Mustached tamarins have jet black pelage on their body and tail and a characteristic white stripe on their upper lip, which gives the appearance of a "white mustache." Mustached tamarins do not have prehensile tails. (Sussman and Kinzey, 1984)
Mustached tamarins do not exhibit sexual dimorphism and there are only minor differences in body and canine size between males and females. On average, adult male mustached tamarins weigh 491 ± 23.0 g and measure 61.2 ± 31.2 cm (n=95), whereas adult females weigh 511.0 ± 49.0 g and measure 62.0 ± 29.0 cm (n=80). (Garber and Teaford, 1986; Rylands and Mittermeier, 2008)
According to Cesar and Bicca-Marques (1999), feeding behaviors are correlated with the relative size and shape of hands in callitrichines. Mixed-species groups of tamarins are observed to form only between species that have different foraging behavior, which reduces direct competition. Consequently, due to the specialization conferred by hand morphology, species with dissimilar hand shapes are usually found in association with each other in such mixed-species groups. This is the case in the mixed-species groups of mustached tamarins and saddle-back tamarins. Saguinus mystax captures exposed insects on branches and thus has evolved relatively wide and short hands, as opposed to saddle-back tamarins, which have made use of longer and more slender appendages to manipulate openings in tree trunks and other substrates to search for insect prey. (Cesar and Bicca-Marques, 1999)
Mustached tamarins usually associate in stable troops, which vary widely in size. For example, the mean group size was found to be 6 to 7 individuals per group in two studies (Garber et al., 1993; Löttker et al., 2004), with a range of 4 to 11 individuals in each group. (Garber, et al., 1993a; Löttker, et al., 2004)
The reproductive strategy of S. mystax is described as polyandrous or polygynous. Each group is typically centered on one breeding female, which is usually also the oldest female. Despite the lack of breeding opportunities, adult non-breeding females may continue to persist in the group, and may ascend to breeding female status in the event of death or illness of the current breeding female. (Garber, et al., 1993a)
A study by Löttker et al (2007) suggests that breeding females use social grooming as incentive to induce adult males and non-breeding offspring to stay in the group as helpers to care for their young. (Löttker, et al., 2007)
Adult mustached tamarins live in highly tolerant and cooperative societies. Garber (1997) estimated that the frequency of cooperative to aggressive acts between adult mustached tamarins was 52:1. Intragroup sexual aggression between male mustached tamarins is exceedingly rare, but mate guarding may be practiced by the dominant breeding adult male during the breeding female’s most fertile periods. (Garber, 1997; Huck, et al., 2004)
Male mustached tamarins may compete for reproductive success via sperm competition and other physiological mechanisms. For example, testes volume in males within a group varied greatly among individuals and this could directly impact reproductive viability of males. (Garber, et al., 1996)
Despite a polyandrous mating system and seemingly a lack of evidence of strong competition or aggression over breeding opportunities, a genetic analysis of paternity in mustached tamarins revealed that 67 to 100% of S. mystax infants in a troop were fathered by the same adult male. Genetic relatedness within a troop is high but both non-related and related adults can co-exist in a troop. There is a need for a better understanding of the critical factors that govern the observed reproductive bias among adult S. mystax males. (Huck, et al., 2005)
Mustached tamarins have characteristic twinned births, with an annual birth peak from November through March. Some S. mystax troops experience 2 birthing cycles, from June to October and in February and March. (Garber, et al., 1993a)
Spatio-genetic analysis of a population of mustached tamarins in Peru by Huck et al. (2007) revealed variable genetic relatedness within a troop. Migration is common among male and female mustached tamarins, but females are often required to travel for longer distances than males before settling down with a new troop due to scarce breeding opportunities in a polyandrous mating society. Matings are generally between non-closely related partners, hence the degree of inbreeding is reduced. (Huck, et al., 2007)
There is an annual birth peak from November through March. Some S. mystax troops experience 2 birthing cycles, from June to October and in February and March.
Maternal infanticide, while rare, has been documented twice in Saguinus species, in S. mystax by Culot et al. (2011) and S. fuscicollis by Herrera et al. (2000). In both cases, infanticides occurred under circumstances of low availability of helpers (2 to 3 male helpers compared to 4 to 5 helpers at other times) and presence of more than 1 breeding female in the troop. Both of these factors lower the likelihood of obtaining sufficient care for the infant within the group.
The single most important determinant of maternal infanticide could be the mother’s perception of low probability of survival of her infant in the group, which is directly caused by external factors in the troops, such as low helper availability. Low helper availability or competition for care with infants from another breeding female in the same troop greatly reduces the chances of survival for infant mustached tamarins. Maternal infanticide may thus represent a strategy to maximize efforts that go into ensuring survival of infants. On the contrary, infanticide of unrelated infant tamarins by male mustached tamarins, which is usually attributed to sexual selection pressures, has never been observed in Saguinus. Males do not gain reproductive advantages from infanticide, as infant mortality has minimum effect on the mother’s fertility status. Female mustached tamarins remain reproductively viable during nursing of their young. (Culot, et al., 2011; Herrera, et al., 2000)
Birth intervals were also shorter during the periods when infanticide occurred (1 to 2.5 months). In Saguinus fuscicollis, which also practices cooperative breeding like S. mystax, the optimal birth spacing is 3 months, so as to allow for efficient care of the young. Shorter birth intervals increase the burden on the troop to care for the young, and this effectively reduces the likelihood of providing adequate care for all of them. (Goldizen, 1989)
Although not demonstrated in S. mystax, care and transport of infants results in significant personal costs for small-sized mustached tamarins. Loss of body mass of carriers of infants has been demonstrated in wild and captive Saguinus oedipus. Cooperative breeding allows the costs of caring for the young to be distributed to other members of a troop to a certain extent, and carriage of infant mustached tamarins is not restricted to certain members of a troop, as members usually take turns in transporting the young when foraging. (Achenbach and Snowdon, 2002; Sanchez, et al., 2005; Sanchez, et al., 2008)
There are inconclusive data on the longest lifespan of mustached tamarins in the wild, though individuals in captivity have been known to live in excess of 20 years. (Weigl, 2005)
Mustached tamarins are social and diurnal animals and usually co-exist in stable groups characterized by infrequent conflicts and relatively low occurrence of sexual interactions within the group. (Heymann, 1996)
Being arboreal, mustached tamarins usually occupy the middle and upper layers of the forest at a height of 10 m above the ground. This is in contrast to their congener, saddle-back tamarins, which occupy the lower layers of the forest. (Buchanan-Smith, et al., 2000; Rylands and Mittermeier, 2008)
Aggressive intergroup encounters between mustached tamarin groups result primarily from resource and mate defense and less from territorial disputes. (Garber, et al., 1993b)
Interestingly, it was observed that in mixed-species groups, the larger S. mystax members are more likely to gain access to disputed food resources over Saguinus fuscicollis members in the same troop. (Norconk, 1990)
Conflicts between neighboring troops of mustached tamarins frequently occur over food resources and especially near important feeding trees. The loss of such feeding opportunities will result in extra foraging efforts by the displaced troop. According to Garber (1988b, p. 27-28), "in those instances in which the troop was excluded from using these nearby feeding sites, mean distance traveled to the next major feeding tree was 331 m. This is considerably greater than the distance traveled to the next major feeding site (59.2 m) after a successful defense." Hence, mustached tamarins that are displaced from feeding by another troop will have to expend more energy to travel longer distances to find another suitable feeding site. (Garber, 1988a)
The development of trichromatic vision in primates has been proposed as an adaptation to allow better detection and identification of fruits in their forested habitats. New World monkeys, such as Saguinus, are unique in having a polymorphic vision system. Only heterozygous female mustached tamarins have trichromatic vision, with the rest retaining dichromatic vision. There is some evidence in the closely related species Saguinus labiatus that those with trichomatic vision "were more efficient at selecting ripe fruits than were dichromats" (Smith et al 2003, p.3159), but this has not been independently demonstrated in S. mystax. (Smith, et al., 2003a)
According to a study by Smith et al. (2003b), mixed-species troops of mustached and saddle-back tamarins were usually led by a mustached tamarin during migration through its home range. Color vision status did not consistently influence the choice of the lead animal of a troop. However, it was observed that a trichromatic female was significantly more likely to lead when the troop was approaching a fruiting tree. This lends support to the hypothesis that trichromats are more endowed to differentiate between fruiting and non-fruiting trees, and thus would be able to identify fruiting trees that are ready for feeding. Color vision is likely to be just one of many factors affecting leadership selection in wild S. mystax and S. fuscicollis troops. (Smith, et al., 2003b)
Vigilance, defined as "observable head movements in stationary animals where scanning is directed beyond arm's reach" (Stojan-Dolar and Heymann, 2010b, p. 327), appears to serve the primary function of predator detection and avoidance in S. mystax. Secondarily, vigilance has also been proposed to maintain group cohesion within one’s own group and to monitor the movement of neighboring troops. Group composition and size affect the vigilance of mustached tamarins. Individuals in mixed-species groups appeared to be less vigilant when feeding and during periods of resting than those not in mixed-species groups. Saguinus mystax members in mixed-species groups also exhibited a greater reduction in vertical vigilance, compared to that in the horizontal direction. One reason may be the positional preferences of Saguinus mystax and S. fuscicollis, which occupy different forest strata. Tamarins in mixed-species groups may share responsibility for group vigilance in the vertical direction; hence, greater reduction in vertical scanning is observed. Development of mixed-species groups provides some evolutionary advantage in enhancing predator detection and avoidance for the troop so as to increase the chances of overall survival of its S. mystax and S. fuscicollis members. (Stojan-Dolar and Heymann, 2010a; Stojan-Dolar and Heymann, 2010b)
Symmetrical quadrupedalism is the dominant type of locomotion in S. mystax (63%), followed by asymmetric quadrupedalism (23%) and leaping (14%). Mustached tamarins also preferentially use more horizontal supports when traveling, and thin and flexible supporting structures when feeding. (Nyakatura and Heymann, 2010)
The movement of S. mystax has been described by Sussman and Kinzey (1984, p. 427) as “quadrupedal, running, and leaping along medium to small branches and jumping among the fine terminal branches and leaves between trees.” (Sussman and Kinzey, 1984)
Although other primates do form sympatric groups, the mixed-species groups of tamarins are among the most stable and permanent of all primate groups. Group cohesion is important in maintaining mixed-species groups, and this can be enhanced by intra-group communication and shared responsibility in predator defense and avoidance. As tamarin species in mixed-species groups may compete for similar resources, spatial segregation between species is important in allowing such mixed-species groups to persist. (Nadjafzadeh and Heymann, 2008)
By differing in locomotor types, support preference, and food/prey selection, and by occupying different strata of their forest habitat, mustached tamarins and saddle-back tamarins are able to co-exist harmoniously in groups without competing for the same scarce resources. (Norconk, 1990)
The home range of mustached tamarins is highly variable, and several troops may co-exist with overlapping territorial limits. A study of mustached tamarins inhabiting Padre Isla (in the Amazon Basin) showed that home ranges of neighboring S. mystax groups overlapped by approximately 38%. (Garber, et al., 1993b)
Allogrooming and scent marking have been studied in S. mystax societies. Allogrooming or social grooming is commonly observed in mustached tamarins, but it is not practiced equally by all members of a troop. In one study by Heymann (1996), an adult male contributed 70% of all grooming observed in a group, without bias to any one of the other members in his troop. The reasons for this asymmetry are not well-characterized but may be attributed to differences in social standing or competition for reproductive success. As mentioned above, breeding females may employ social grooming as a way of encouraging other members in her troop to stay to assist in parental care duties. (Heymann, 1996; Löttker, et al., 2007)
The use of scent marking for territorial demarcation is variable among Saguinus species. In both wild and captive S. mystax, there is little evidence for the use of scent marking in territorial defense. (Heymann, 2000)
Scent marking functions prominently in intra-group communication and female mustached tamarins are more likely to engage in scent marking behavior, compared to males. On the contrary, male mustached tamarins are more likely to respond to scent marks of the opposite sex, which may be related to mate selection. Mustached tamarins do not engage in "collective scent marking" or allomarking, unlike in S. fuscicollis. (Heymann, 2001)
The rates of scent marking by mustached tamarins are directly proportional to the duration of occupation of areas by the troop. Intense scent marking in more frequented areas enhances the effectiveness of olfactory communication between members of the same troop. (Heymann, 1998)
Vocalization has also been demonstrated to be a form of communication in S. mystax, such as in situations where a mustached tamarin becomes separated from its troop. According to Snowdon and Hodun (1985, p. 211), "The long-call structure of the moustached tamarin is similar to that of its sympatric tamarin species, saddleback tamarins. In both species the calls last 2 to 3 seconds, consist of several short, frequency-modulated syllables, and has a frequency range of 8 to 12 kHz". The same study also noted that "nonbreeding adult females gave fewer calls" and they were also slower to make the first long call upon separation. This could reflect "the relatively low status of nonreproductive mature females" (p. 211) in their troop, which is usually centered on a single breeding female. Members of a troop are able to recognize members of their troops by responding to long calls from separated members. This ability to distinguish individual members suggests that a S. mystax troop in the wild is able to maintain its integrity by ensuring that all members are accounted for. (Snowdon and Hodun, 1985)
Early morning vocalizations and subsequent coordinated movement patterns within mixed-species troops of mustached tamarins and saddle-back tamarins are also crucial in maintaining group integrity on a daily basis. (Norconk, 1990)
Being frugivorous-insectivorous, mustached tamarins feed on fruits, flowers, and nectar, insects, and plant exudates. Food sources like gums and soil appear to supplement nutrients and minerals lacking in their main diet of fruits and insects. (Heymann and Hartmann, 1991; Heymann, et al., 2000)
Mustached tamarins typically only feed on a small number of plant species in their home range. However, feeding trees are numerous and scattered throughout their home range. Feeding trees are usually continuously fruiting and produce a small amount of fruits daily, hence mustached tamarins may visit the same trees regularly over a span of several months to exploit the resources. (Garber, et al., 1993b)
In a group of mustached tamarins in northeastern Peru, up to a third of feeding time was spent feeding on nectar from Symphonia globulifera in the dry season. Mustached tamarins concentrated their foraging efforts on trees that yielded more nectar, despite having to travel greater distances between feeding sessions in some cases. Therefore, proximity of feeding trees from one another did not predict foraging patterns, as mustached tamarins preferentially chose feeding trees that allowed them to feed for longer periods of time instead of trees that were closer and would thus minimize traveling time from one tree to another. (Garber, 1988b; Garber, 1989)
Although feeding trees are typically scattered throughout their home range, mustached tamarins are able to remember the locations of the important feeding trees to minimize efforts in foraging. The use of spatial memory and learning in foraging are important because they provide "an efficient means of exploiting a widely scattered set of predictable feeding sites" (Garber, 1989, p. 212). (Garber, 1989)
Gum feeding is highly seasonal, but it is a major dietary staple during dry and early wet seasons when other food sources are scarce. Furthermore, gum exudates balance mineral intake, which will otherwise suffer from the effects of a low-calcium and high-phosphorus insectivorous diet. (Sussman and Kinzey, 1984)
Since mustached tamarins lack the dental specialization to gouge holes into tree bark, gum feeding is "dependent principally on either natural weathering of the bark or on the parasitic activity of woodboring insects, or both" (Garber, 1992, p. 471). (Garber, 1992)
Heymann and Smith (1999) found that Saguinus mystax concentrated gum feeding in the afternoon. They hypothesized that this may be "a behavioral strategy to prolong the time that the gums are retained in the gastrointestinal tract" (p. 468). Prolonged passage allows for better digestion and more complete microbial fermentation of the substrates. This in turn yields nutritional benefits while providing these small animals with a means to generate heat during the night via the fermentation process. (Heymann and Smith, 1999)
Garber (1992) described mustached tamarins as exhibiting "a highly opportunistic foraging pattern," with "seasonal exudate feeding, occasional trunk foraging patterns, and small-branch fruit and insect feeding" (p. 471). (Garber, 1992)
The main vertebrate prey for mustached tamarins includes "katydids (Tettigoniidae, Orthoptera), stick grasshoppers (Proscopiidae, Orthoptera), and spiders (Araneidae), although lizards (Squamata) and frogs (Anura) were also taken" (Smith, 2000, p. 315). Mustached tamarins also feed on nestling birds, albeit less frequently. They forage for prey at higher levels within the forest strata than Saguinus fuscicollis (average of 8.84 m vs. 1.50 m; Smith 2000), and also capture most prey from slender and horizontal substrates. (Smith, 2000)
Due to their small size, mustached tamarins are vulnerable to predation by a large number of terrestrial predators, such as tayras (Eira barbara), ocelots (Leopardus pardalis), and jaguarundis (Puma yagouaroundi). Large snakes like Boa constrictor and birds of prey are also important predators. (Oversluijs Vasquez and Heymann, 2001)
Cooperative defense against predators was observed in a tribe of mustached tamarins in northeastern Peru. Members of this tribe successfully rescued a mustached tamarin that was being attacked by a Boa constrictor by counter-attacking the predator. The tribe subsequently avoided low heights for a week after the attack, as further deterrence to attacks by snakes. (Tello, et al., 2002)
In general, mustached tamarins counter predators by avoiding attracting attention. Mustached tamarins are camouflaged in densely foliated areas and they carefully select resting and sleeping sites that have lower chances of being exposed. They may also choose resting sites that are physically isolated from surrounding vegetation, as this would increase the likelihood of them being able to detect approaching predators. (Smith, et al., 2007)
Mustached tamarins play an important ecological role in their habitat by dispersing seeds of plant species in primary and secondary rain forest, and thus indirectly impact forest regeneration and maintenance. (Culot, et al., 2010)
As mustached tamarins are opportunistic feeders and are able to explore many kinds of plant resources, they are able to disperse a great variety of seed species. (Herrera, et al., 2003; Knogge and Heymann, 2003)
Due to their small size, there is a limit to the size of seeds that they can disperse. Seasonal changes in diet, sleeping and resting patterns, and variation in foraging behavior and migration may also affect their contribution to seed dispersal in the rainforest. (Muñoz Lazo, et al., 2011)
On a negative note, mustached tamarins have been observed to be highly destructive in their nectar-feeding activities but the widespread ecological impact of this has not been demonstrated. (Garber, 1988b)
Mustached tamarins that foraged near human settlements were found to have higher prevalence of a primate parasite, Prosthenorchis elegans. However, in the same study by Wentz et al. (2010), mustached tamarins were not found to be infected by human parasites even though they lived in close proximity to human communities with high rates of infestation of nematodes such as Ascaris lumbricoides and hookworms. (Wenz, et al., 2010)
Saguinus mystax, like other tamarin species, has been used extensively in biomedical research, e.g., in the development of the hepatitis A vaccine. (Ebert, et al., 1978)
Although commensally associated with human communities, there is no evidence for adverse economic effects on humans.
Mustached tamarins are on the least concern list of animals on The IUCN Red List of Threatened Species (last assessed in 2008). Populations of wild mustached tamarins have been noted to be stable, although habitat destruction remains a threat to species living in the Amazonian rainforest. (Rylands and Mittermeier, 2008)
The effects of agriculture on S. mystax populations in Peru have been studied. Populations recovered and even exceeded pre-agricultural numbers due to "increased reproductive rate, early breeding, and reduced infant mortality", while "immigration seemed to play a minor role" (Ramirez, 1984, p. 258). (Glander, et al., 1984; Ramirez, 1984)
Genetic analysis supports the division of tamarin taxa into small-bodied and large-bodied clades (Matauschek et al., 2011, p. 564), of which S. mystax is a member of the large-bodied clade. Molecular phylogenetic evidence also supports the “phyletic dwarfism” hypothesis in Callitrichinae, which is "defined as a gradient in morphological size partially correlated with evolutionary time" (Perelman et al., 2011, p. 4). In this case, Saguinus is the first to diverge, followed by the remaining callitrichines in order of decreasing body size. Within Saguinus, phylogenetic analysis of mitochrondrial DNA has demonstrated that Saguinus labiatus is the closest relative of S. mystax, with the two taxa diverging about 1.15 mya. (Matauschek, et al., 2011; Perelman, et al., 2011; Tagliaro, et al., 2005)
Jayne Lim (author), Yale University, Eric Sargis (editor), Yale University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
Stock photo of a dragonfly head on. This is a photograph of a dragonfly flying directly at the camera.