Pygmy Marmoset (Cebuella pygmaea)

MORPHOLOGY: The average body mass of an adult pygmy marmoset ranges between 85 and 140 grams with a mean mass of 119 grams, making it the smallest New World primate (Soini, 1988). The total length of adults ranges from 331 to 362 millimeters, with an average of 339 millimeters (Soini, 1988). The dental formula on the upper and lower jaw is 2:1:3:2 (Ankel-Simons, 2000). This small size of the pygmy marmoset is the result of exceptional phyletic dwarfism (Ferrari, 1993); this species evolved from a larger sized callitrichid. This species has thumbs, which are nonopposable, and the nails are claw-like except for the first digit on each toe. The claws (tegulae) are used to cling to large vertical supports (Kinzey et al., 1975). The forelimbs are relatively long, but the radii are relatively short having an advantage in the lateral placement of the forelimbs when vertically clinging when feeding (Thorington and Thorington, 1989). The canines are shaped like incisors, which are equal in shape to the canines, a possible adaptation for excavating exudate holes (Coimbra-Filho and Mittermeier, 1976, 1977). The adult pygmy marmoset has a dorsal pelage coloration that is mostly tawny agouti (Soini, 1988). Adults have a dark gray or blackish semi-striated pattern from the legs to the mid-dorsum (Soini, 1988); in immature individuals the pelage from the legs to the lower back is gray-ticked (Soini, 1988). Ventrally, adults from the chest downwards have a coloration that ranges from drab or light ochraceous to white (Soini, 1988). On the neck, under the chin, there is sometimes a faint, vertical streak of the same color as the ventral pelage (Soini, 1988). The tail of this species is faintly to conspicuously annulated (Soini, 1988). The tail has a small black terminal hair tuft (Aquino and Encarnacion, 1994). The scrotum of adult males is mottled with heavy black pigmentation, and the external genitalia of females are not pigmented (Soini, 1988). Black pelage borders the anogenital region of adult males and females (Soini, 1988); this is developed in the juvenile (5-12 months) (Soini, 1988). On the face there is a vertical nasal ridge stripe that is buffy to white in color (Soini, 1988). White spots may occur over either mouth corner (Soini, 1988).

The pygmy marmoset is divided into two subspecies, each having a slightly different pelage coloration:

• Cebuella pygmaea pygmaea: The ventral side of this subspecies is buffy colored (Groves, 2001).
• Cebuella pygmaea niveiventris: The ventral side of this subspecies is gray colored (Groves, 2001).

RANGE:
The pygmy marmoset is found in the following countries: Bolivia, Brazil, Colombia, Ecuador, and Peru (Soini, 1988; Buchanan-Smith et al., 2000; Bennett et al., 2001). This species ranges from the south bank of Rio Caqueta in northern Colombia to the northern banks of the Rio Orthon-Manupiri or the Rio Madre de Dios in northern Bolivia and southeastern Peru (Soini, 1988). In Bolivia, Izawa and Bejarano (1981) found pygmy marmosets to be distributed in Monte bajo and Barbecho tupido along the rivers between Rio Acre and Rio Tahuamanu. In Colombia, this species is found in Amacayacu National Park (Hernandez-Camacho and Defler, 1985). This species prefers to live in forests at a river’s edge and those found in a flood plain, with the general habitat being described as heterogeneous, evergreen, mesophytic lowland forest (Soini, 1988). Living near water may aid in protection against predators as well as contribute to an abundance of arthropods and exudate sources (Aquino and Encarnacion, 1994). The highest population concentrations are often found in forests on the edges of river and their backwaters (Soini, 1988). In the Cuyabeno Reserve, Ecuador, this species is found in igapo and flooded white-water forests (varzea) (de le Torre et al., 1995; de la Torre, 1996). Pygmy marmosets will live in proximity to human settlements, sometimes in degraded woods that are found between pastures and crop fields (Soini, 1988; Moynihan, 1976).

ECOLOGY:
The pygmy marmoset is a gummivore-insectivore and occasionally eats fruit, buds, flowers, nectar, and vertebrates (Kinzey, 1997; Soini, 1982, 1988; Ramirez, 1985a, b; Coimbra-Filho and Mittermeier, 1977). Fruit consumption may increase with the increased availability of succulent fruits such as those in an orchard or Ficus species (Soini, 1982, 1988). Vertebrate consumption seems to be confined to the lizards of the genus Anolis (Soini, 1988). Observed insect orders consumed include: Coleoptera, Homoptera, Hymenoptera, Lepidoptera, and Orthoptera, with grasshoppers being the most popular prey item (Moynihan, 1976; Ramirez et al., 1977; Soini, 1982; Soini, 1988). Snowdon and Pola (1982) found that in captive individuals, insects are captured with the hands and that at least 75% of the time they are eaten head first. Butterflies feeding on the exudate holes made by pygmy marmosets are often stalked and captured (Soini, 1988). This species is the most specialized gummivore amongst the callitrichids (Garber, 1992). Ramirez et al. (1977) found that the group they were studying spent 67% of the time consuming exudates and 33% on insect foraging.

The pygmy marmoset has been found to feed on exudates (sap and gum) of over 60 species of plants (Soini, 1988). The types of plants include trees, vines, and hemiepiphytes (Soini, 1988). The most important sources of exudates come from the plant species Vochysia lomatophylla, Spondias mombin, and Parkia oppositifolia (Soini, 1988). Other important exudate sources come from Qualea amoena, Inga, and Trichilia (Soini, 1988). The pygmy marmoset has been found to utilize exudates sources from four plant families: Vochysiaceae, Leguminosae, Anacardiaceae, and Meliaceae (Soini, 1988). A group will have one principal tree used as an exudate source, with the dominant breeding pair and young offspring having the most access to the source and older offspring generally have a more restricted access to this source (Soini, 1988). Secondary exudate sources, such as trees or lianas (vines), are also used by the dominant breeding pair and younger offspring (Soini, 1988). When the primary feeding tree fails to yield sufficient exudates, then the group may switch to a secondary source within the home range, or it may move to a new home range (Soini, 1988). Zingg and Martin (2001) found that groups will feed on exudates more in the morning and evening, than in the afternoon, and a decrease in activity at noon may relate microbial fermentation in the gut to digest the exudates. Addington (1998) found in captivity that aggression associated with feeding is rare, resulting from the cooperatively breeding and the cooperative inducement of exudate holes. Pygmy marmosets will use their lower anterior dentition (incisors and canines) to induce exudate flow (Coimbra-Filho and Mittermeier, 1977). Exudate consumption may have evolved to reduce competition with fruit eating mammals and birds (Coimbra-Filho and Mittermeier, 1977).

In Brazil, van Roosmalen and van Roosmalen (1997) found that the tree species used as exudate sources were: Enterolobium schomburgkii (Mimosaceae), Inga edulis (Mimosaceae), Inga ingoides (Mimosaceae), and Ficus guianensis (Moraceae). Enterolobium shomburgkii was found to be the principal food source for pygmy marmosets, visited on a daily basis (van Roosmalen and van Roosmalen, 1997).

In Ecuador, Yepez et al., 2005 found that pygmy marmoset groups at four different sites had different exudate sources: Sterculia apetala at San Pablo, Cedrela odorata at Sacha, Inga marginata at Amazoonico, and Parkia balslevii at Zancudo. The four different groups were found to exploit eighteen different exudate sources, with all sources being trees except one that was a liana (Yepez et al., 2005). Exudate source choice was not found to relate to availability locally or by random usage (Yepez et al., 2005). Source choice may relate to social transmission of feeding preferences, i.e., individual groups develop a preference for certain trees and this is passed down over the generations (Yepez et al., 2005).

Pygmy marmosets obtain most of their water from exudates, but they will lick drops of water or dew from boles, branches, and liana stems (Soini, 1988). This species has not been found to descend to ground level or to the water's edge to drink (Soini, 1988).

The mean size for a pygmy marmoset group is 5.1 individuals and can range from 2 to 9 individuals (Soini, 1993, 1988). Castro and Soini (1977) report groups in Peru range between 5 and 10 individuals and Moynihan (1976) report group sizes ranging between 3 and 6 individuals in Colombia. Hernandez-Camacho and Cooper (1976) found group sizes in Colombia to range from 10 to 15 individuals. In Ecuador, de la Torre (1996) found group sizes to range from 3 to 8 individuals. Peres (1988) found that in Lago da Fortuna, Brazil, mean group sizes were 4 individuals. A group consists of a breeding pair and their offspring and sometimes by a third adult or subadult (Soini, 1988). Pygmy marmoset groups differ from other sympatric callitrichid groups, such as Saguinus fuscicollis and Saguinus mystax, in having fewer adults and more non-adults (Soini, 1988, 1982; Harrison and Tardif, 1994). This intolerance to other adults may be a reflection of the use of exudates as the primary food source, which is a more stable food source than the fruits consumed by other callitrichids in the region (Soini, 1988). Harrison and Tardif (1994) suggest that there may be more non-adults in pygmy marmoset groups because of high fertility, low infant mortality, late average age of dispersal from natal groups, or a low rate of adult immigration.

Daily activity generally takes place between 0 to 20 meters above the forest floor (Soini, 1988). Youlatos (1999) found that in Yasuni National Park, Ecuador, groups spend most of the time in heights below 10 meters, feeding on sap and foraging for insects. Soini (1988) found that social grooming, rest, and play tends to occur between 10 and 20 meters from the forest floor, roosting sites 6-12 meters, insect foraging from 3-14 meters, exudate feeding (secondary zone) from 6-15 meters, exudate feeding (primary zone) from 0-7 meters, and traveling to and from the roost site between 1-3 meters. Daily group movement does not normally exceed 100 meters in a day (Soini, 1988). However, solitary individuals who are searching for a mate can travel up to 850 meters in a day (Soini, 1988). Group activity generally begins shortly after sunrise and ceases, that is the group returns to the roost site, shortly before sunset (Soini, 1988). Activities in the group consist mostly of exudate feeding, insect foraging, social grooming and huddling, resting, watching, and play (Soini, 1988). Heavy rains can have a great influence on activity patterns, decreasing the amount of time directed towards feeding and increasing the amount of inactivity of the group (Soini, 1988). A typical day for a group of pygmy marmosets includes: 1. feeding on exudates for the first 30 minutes to and hour and a half, then 2. a period of basking, huddling, grooming, and play, followed by insect foraging and then exudate foraging, 3. around noon a second period of resting, grooming, and play with some feeding, and finally 4. intensive feeding from the early evening until they head back to the roost to sleep (Soini, 1988).

In Peru, Ramirez et al. (1977) found that pygmy marmosets spent 32% of their time eating exudate and excavating exudate holes, 16% foraging for insects, 11% traveling, 32% inactive, 9% other activities such as grooming and play. Ramirez et al. (1977) found that three main plat sources were used for exudate: Quararibea rhombifolia (44% of the time), Trichilia sp. (36% of the time), and a vine Cheiloclinium cognatum (20% of the time). Ramirez et al. (1977) found that pygmy marmosets in Peru excavate exudate holes mainly on the trunk of the tree and sometimes on major tree branches. Pygmy marmosets will excavate holes from the bottom up on an individual tree, where one will find a higher percentage of older holes on the bottom and increasingly older holes as one ascends (Ramirez et al., 1977). The shape of the exudate holes differs depending on the tree species, where Q. rhombifolia holes are round and holes excavated in Trichilia sp. are oblong (Ramirez et al., 1977). Pygmy marmosets will excavate holes in clumps or in horizontal bands (Ramirez et al., 1977). When foraging for arthropods, pygmy marmosets in Peru were found to spend 75% of the time between 5 and 15 meters above the ground, 24% below 5 meters, and only 1% above 15 meters (Ramirez et al., 1977). Ramirez et al. (1977) found that there was little coordination of group activities. Individuals will rest during the day 10 to 15 meters above ground in thick foliage on large branches, and in the early morning they are generally exposed to the sun (Ramirez et al., 1977).

Where a group of pygmy marmosets sleep during the night is called their roost site. Members of a group will roost together, huddling into a single marmoset mass (Soini, 1988). A roost site will be used many times and/or continuously over many nights (Soini, 1988). Roost sites are located in small to medium sized trees (10-20 meters tall), in the basal or middle crown, and situated 7 to 10 meters above the ground (Soini, 1988). Roost sites can also be found in large trees, large woody vines, or a dead bole (Soini, 1988). The roost tends to be a crotch in the tree, the proximal part of a branch that meets with the trunk or the stump of an old, broken-off tree branch (Soini, 1988). The roost can also be a clump of epiphytes or the remnants of an old termite nest attached to a bole (Soini, 1988). Roosts are often, but not always, concealed by a mass of twigs, vines, and/or epiphytic growth (Soini, 1988). Groups will have two or three roost trees in their home range, with one tree used continuously and the other(s) used sporadically (Soini, 1988). Groups will leave the roost in a single file line, headed by a dominant adult (Soini, 1988). Mothers may nurse infants before leave the roost tree (Soini, 1988). A dominant adult will initiate group movement in the evening back to the roost tree by emitting J-calls, and group members fall asleep shortly after reaching the roost (Soini, 1988).

The home range of the pygmy marmoset is determined by the distribution of trees used as a source of gum, and when gum yield drops in a certain area the group will move on to a new area (Soini, 1993, 1988). The time spent in a given home range is also dependant on the tree species used as exudate sources, such that groups with the species Spondias mombin or Qualea amoena will occupy the home range for a longer period of time than groups occupying home ranges with Vochysia or Parkia (Soini, 1988). Son or daughter groups will sometimes take up residence in areas vacated by the parental group (Soini, 1988). Time spent in a given home range can last from a few months to several years (Soini, 1988). Home ranges range in size from 0.1 to 0.5 hectares (Soini, 1988). The members of a group generally focus their feeding on one particular tree, which becomes the place for social activity (Soini, 1993).

Predators of pygmy marmosets include: the tayra (Eira barbara), the ocelot (Leopardus pardalis), the oncilla (Leopardus tigrinus), the margay (Leopardus wiedii), the jaguarondi (Herpailurus yaguarondi), pit viper (Bothrops atrox), and birds of prey (accipitrids and falconids) (Soini, 1988).

The pygmy marmoset has competition over food sources from other species, which includes both vertebrates and invertebrates (Soini, 1988). The most important competition over exudate source, apart from other primate species, is two special of arboreal ants (Soini, 1988). The ants will feed on the exudate holes at night, when pygmy marmoset groups are asleep (Soini, 1988). Ramirez (1985) found that in Peru, the sympatric callitrichid Saguinus mystax will parasitize exudate holes used by pygmy marmosets. Passerine birds tend to be competitors for the same insects that pygmy marmosets forage for in the trees (Soini, 1988).

LOCOMOTION:
The pygmy marmoset runs or walks quadrupedally along branches and vines in the forest (Kinzey, 1997; Kinzey et al., 1975; Soini, 1988). They are also capable of vertical clinging and leaping, and tend to feed on gum while clinging on a tree (Kinzey, 1997; Soini, 1988; Buchanan-Smith et al., 2000). Pygmy marmosets generally are found leaping in the understory, where vertical supports are of a small diameter (Soini, 1988). When leaping, an individual will not leap upwards or downwards, rather by horizontal arching or by diagonally descending (Soini, 1988). Kinzey et al. (1975) found that 75% of leaps were to and/or from vertical supports. Pygmy marmosets will descend vertical supports headfirst (Soini, 1988). Ascension of vertical boles of a large diameter is performed by alternately pushing with both feet then pulling by both hands (Soini, 1988). This species will also move quadrupedally on the underside of a horizontal or diagonal branches or vines (lianas) (Soini, 1988). Pygmy marmosets can make lizard-like movements, turning 180 degrees on a slender support, whether horizontal or vertical (Soini, 1988). Social resting, huddling, and grooming are done on a horizontal support (Soini, 1988). Arthropods are procured by approaching with a slow stalking gait then capturing with a rapid pouncing leap (Kinzey et al., 1975).

Youlatos (1999) found that in Yasuni National Park, Ecuador, quadrupedal walk and bound was the most dominant locomotor mode and scansorial locomotion ("quadrupedal progression using the claws along large vertical supports") ranked second. Leaps and vertical leaps were also found to be important forms of locomotion (Youlatos, 1999). Lianas were the supports used most frequently for traveling (Youlatos, 1999). Quadrupedal walk/bound occurred on supports <5 centimeters and scansorial locomotion occurred on supports >10 centimeters (Youlatos, 1999). More than half of all leaps were initiated from supports <5 centimeters, and vertical leaps were initiated from supports between 2 and 10 centimeters (Youlatos, 1999). Long vertical leaps tended to be initiated on larger supports than the leaps were terminated on (Youlatos, 1999). During feeding, scansorial locomotion was used most frequently (Youlatos, 1999). For foraging on insects, the pygmy marmoset was found to employ quadrupedal walk/bound most frequently (Youlatos, 1999). Foraging for insects occurred mostly on lianas (Youlatos, 1999).

SOCIAL BEHAVIOR:
In the pygmy marmoset, only the dominant female bares young, and she may mate with more than one male suggesting a possible polyandrous mating system (Soini, 1988). In at least one instance in captivity, more than one female in a group has given birth, which may have been allowed by the dominant female because reproductive success was not compromised in there was enough helpers and enough food available (Schropel, 1998). The dominant female is dominant over all other members in the group including the males (Soini, 1987). All group members share in the responsibility for carrying the young around which is done at all times (Ferrari, 1993). Both males and females emigrate from their natal groups (Soini, 1988). Dominant females become aggressive towards other group members during the third month of pregnancy, and this aggression by the dominant female might be the catalyst that pushes the subadults away from the main group and eventual emigration (Soini, 1988). When subadults disperse from their natal group they may approach other groups, emitting long calls, in order to search for other subadults that are being peripheralized (Soini, 1982, 1988).

Social grooming has been found to be important in the daily routine of the pygmy marmoset group (Soini, 1988; Christen, 1974; Ramirez et al., 1977; Larson et al., 1982). Every member of the group participates in social grooming, but adults have been found to do it more frequently (Soini, 1988). Social grooming tends to take pace more during the major resting bouts, in the late morning and early afternoon (Soini, 1988; Ramirez et al., 1977). In a captive study it was found that subordinate females would groom more dominant females at a higher frequency than grooming other subordinate females (Christen, 1974). In the same captive study it was also found that males would groom all females in the same frequency, and that females would groom males equally (Christen, 1974).

Play is performed mainly by infant, juvenile, and subadult pygmy marmosets, with adults rarely, if all, engaging in play (Soini, 1988). Two types of play are found, solitary and social play (Soini, 1988). Solitary play includes: acrobatic hanging, leaping and running, and imitating the stalking and catching of insects (Soini, 1988). Chasing and rough-and-tumble play are the main types of social play, where play groups range in size from 2 to 4 individuals (Soini, 1988). Play tends to occur during the major resting bouts, in the late morning and early afternoon (Soini, 1988). Play periodically occurs in the crown of the group's feeding tree or another large tree in the group's home range, often in the same places (Soini, 1988).

In a captive experiment, Eglash and Snowdon (1983) showed that pygmy marmosets might display a precursor of mirror-image self-recognition. Individuals were found to behave the same way in a chimpanzee, Pan troglodytes, does when presented with a mirror (Eglash and Snowdon, 1983). Some individuals used the mirrors to send genital display signals to another individual that was unseen (Eglash and Snowdon, 1983).

VOCAL COMMUNICATION:
long call: This is a series of 2 to 7 high-pitched, long notes that sound like "kwii-kwii-kwii…" (Soini, 1988). This call often has a prefix trill or J-call (Soini, 1988). This call has a common occurrence (Soini, 1988). This call is heard during situations of extra- and intragroup long distance contact (Soini, 1988). All members of the group emit this call except for infants under 2 months of age (Soini, 1988). This call functions to locate potential mates and for territorial reasons, and is motivated by a desire for contact and distress (Soini, 1988). The response to this call is for the receiver to approach the caller and/or emit long call (Soini, 1988).

duetting: This is a long call with a tonal chatter prefix sounding like "tsiki-tsiki-tsiki-kwii-kwii…", which is emitted alternately by the female and the male (Soini, 1988). This call rarely occurs (Soini, 1988). This call is heard during the establishment of a territory and is emitted by newly formed couples (Soini, 1988). This call serves as a territorial defense call and to strengthen the pair bond (Soini, 1988). This call has aggressive and territorial motivations (Soini, 1988).

tonal chatter: This is a rapid series of tsik notes "tsiki-tsiki-tsiki…" that is often accompanied by a closed mouth trill prefix (Soini, 1988). This call is very rare (Soini, 1988). This call is emitted by only adults (Soini, 1988). This call functions to achieve contact and is motivated by distress (Soini, 1988). The response to this call is often a closed mouth trill or antiphonal (Soini, 1988).

low tonal chatter: This call is like tonal chatter, but of a lower tone, emitted with the mouth closed (Soini, 1988). This call is uncommon (Soini, 1988). This call is heard when an individual is calling in the darkness, usually from a roost (Soini, 1988). This call is only emitted by adults (Soini, 1988). This call functions to achieve contact and is motivated by distress (Soini, 1988). The response to this call is usually closed mouth trill or antiphonal (Soini, 1988).

J-call: This call is a high-pitched, ringing trilling, which is emitted with the mouth open (Soini, 1988). The duration of this call is about 1 second (Snowdon, 1989). This call is very common (Soini, 1988). This call is heard when an individual calls for entire group movement and when the group arrives (Soini, 1988; Snowdon and Cleveland, 1980). Individual pygmy marmosets can recognize each other by the individual J-calls (Snowdon and Cleveland, 1980). This call is emitted by all individuals except infants (Soini, 1988). This call functions to maintain group cohesion, and this is responded to by approaching the caller (Soini, 1988). In German this is called Trillerlaute (Soini, 1988). Snowdon and Cleveland (1984) found that this and other contact calls have rules: 1) "each animal should call once before an animal repeats a call" and 2) "the preferred order of calling is animal 1, followed by animal 2, followed by animal 3, or combination of that order."

open mouth trill: This trill-like sound is emitted before aggressive or agonistic encounters (Pola and Snowdon, 1975). This call is emitted with the mouth open and is very common (Soini, 1988). The mean bandwidth for open mouth trill is 3.9 kilohertz and the mean duration is 294 milliseconds (Snowdon and Pola, 1978). This call is also heard in situations of intragroup contact over short to moderately long distances (Soini, 1988). This call is emitted by all individuals except for infants (Soini, 1988). This call functions to achieve contact and is motivated by slight distress (Soini, 1988). The response to this call is an increase in agonistic activities, antiphonal, or none (Soini, 1988). In German this is called Trillerlaute (Soini, 1988). In a captive experiment, Elowson and Snowdon (1994) found that individuals in a group will change the acoustical structure of trills when presented with another pygmy marmoset group not seen previously, suggesting plasticity in the structure of contact calls; this plasticity in calls might assist in the development of social relationships. Snowdon and Cleveland (1984) found that this and other contact calls have rules: 1) "each animal should call once before an animal repeats a call" and 2) "the preferred order of calling is animal 1, followed by animal 2, followed by animal 3, or combination of that order."

closed mouth trill: This trill-like sound is heard by the pygmy marmoset when it is calm and moving through its environment (Pola and Snowdon, 1975). This vocalization is emitted with the mouth closed (Soini, 1988). The mean bandwidth is 3.8 kilohertz and the mean duration is 175.2 milliseconds (Snowdon and Pola, 1978). This type of call is very common (Soini, 1988). This is heard during intragroup short-range contact, progression (Soini, 1988). This is emitted by all individuals except for infants (Soini, 1988). This call functions to maintain contact and is motivated by mild distress (Soini, 1988). The response to this vocalization is antiphonal (Soini, 1988). In a captive experiment, Elowson and Snowdon (1994) found that individuals in a group will change the acoustical structure of trills when presented with another pygmy marmoset group not seen previously, suggesting plasticity in the structure of contact calls; this plasticity in calls might assist in the development of social relationships. Snowdon and Cleveland (1984) found that this and other contact calls have rules: 1) "each animal should call once before an animal repeats a call" and 2) "the preferred order of calling is animal 1, followed by animal 2, followed by animal 3, or combination of that order."

quiet trill: This is a soft trilling, which is emitted with the mouth closed (Soini, 1988). The mean bandwidth for this call is 1 kilohertz and the mean duration is 173.2 milliseconds (Snowdon and Pola, 1978). This call is very common (Soini, 1988). This call is heard during situations of intragroup close range contact when the situation is calm (Soini, 1988). Individuals will emit quiet trill in close proximity of the receiver (1 meter) (Snowdon and Pola, 1978). All individual emit this call (Soini, 1988). This call functions to maintain contact and is motivated by well-being and friendly intentions (Soini, 1988). The response to this vocalization is antiphonal (Soini, 1988). In German this call is called Stimmfuhlungslaut (Soini, 1988). In a captive experiment, Elowson and Snowdon (1994) found that individuals in a group will change the acoustical structure of trills when presented with another pygmy marmoset group not seen previously, suggesting plasticity in the structure of contact calls; this plasticity in calls might assist in the development of social relationships. Snowdon and Cleveland (1984) found that this and other contact calls have rules: 1) "each animal should call once before an animal repeats a call" and 2) "the preferred order of calling is animal 1, followed by animal 2, followed by animal 3, or combination of that order."

alerting call: This is a high-pitched, soft, and short "kik" note (Soini, 1988). This call is very common (Soini, 1988). This is heard when there is an appearance of a low-risk potential predator (Soini, 1988). This call is heard by all individuals except for infants (Soini, 1988). This call functions as a warning call of low intensity and is motivated by alarm (Soini, 1988). This is also called a type A call (Soini, 1988).

warning call: This is one or several high-pitched and loud "kiik" notes (Soini, 1988). The occurrence of this call is very common (Soini, 1988). This call is heard when there is an appearance of a high-risk predator (Soini, 1988). This call is heard by all individuals except infants (Soini, 1988). This call functions as a warning call of high intensity and is motivated by high alarm (Soini, 1988). In German this is called Warnlaut (Soini, 1988).

click: This is a call composed of short, atonal notes, having a low intensity, where the mouth is closed (Soini, 1988). This is a common call for the pygmy marmoset (Soini, 1988). This call is heard during mildly disturbing or exciting non-social situations (Soini, 1988). This call is heard from all individuals except for infants from the second or third week (Soini, 1988). This call functions as a mobbing call and is motivated by mild alarm or excitement (Soini, 1988). In German this is called Schnalzlaut (Soini, 1988).

tonal-squeak click: This vocalization is a click with a tonal segment added (Soini, 1988). This call is common (Soini, 1988). This call is heard during disturbing non-social situations (Soini, 1988). All individuals emit this call (Soini, 1988). This call functions as a mobbing call and is motivated by high alarm or high excitement (Soini, 1988). In German this is called Schnalzlaut (Soini, 1988).

tsik call: This call is composed of single, sharp "tsik" notes (Soini, 1988). This call is common (Soini, 1988). This call is heard during situations that are sudden, highly alarming, or disturbing (Soini, 1988). This call is emitted by all individuals, but most frequently with adults (Soini, 1988). This call functions as a mobbing call and is motivated by intense alarm (Soini, 1988).

chatter: This is a low-pitched, atonal rattle that sounds like "teke-teke-teke…" (Soini, 1988). This call is common (Soini, 1988). This call is heard during intraspecies agonistic interactions and during sexual chase (Soini, 1988). All individuals except for infants under two months of age emit this call (Soini, 1988). This call functions to communicate defensive and offensive threat and has hostile motivations (Soini, 1988). The response to this call is often avoidance or submissive behavior (Soini, 1988). In German this is called Keckern (Soini, 1988).

tsak chatter: This is tsak notes uttered in a rapid series (Soini, 1988). This call is very rare (Soini, 1988). This call is heard during highly frightening or disturbing situations (Soini, 1988). All individuals emit this vocalization (Soini, 1988). This call functions to communicate alarm and rage and is motivated by intense alarm and/or rage (Soini, 1988).

play chatter: This is when tsik notes are emitted in a rapid series, often accompanied by a trill prefix (Soini, 1988). This is a common call (Soini, 1988). This is heard during juvenile play and is emitted by juveniles (Soini, 1988). This functions to communicate play and is motivated by excitement (Soini, 1988).

type A screech: This is a loud and harsh screech (Soini, 1988). This call has a rare occurrence (Soini, 1988). This call is heard during sudden, highly painful, or frightening situations (Soini, 1988). All individuals emit this vocalization (Soini, 1988). This functions as the most intense alarm, and may stop further aggression (Soini, 1988). This call is motivated by intense fear (Soini, 1988). In German this is called Angstschrei (Soini, 1988).

intergroup screech: This is a long duration screech with clear tonal bands (Soini, 1988). This call is heard in situations of intergroup territorial defense (Soini, 1988). Adults emit this call (Soini, 1988). This call functions to communicate territorial defense and has hostile motivations (Soini, 1988).

type B screech: This is a call composed of hard screech note(s), often accompanied by tsak chatter (Soini, 1988). This call is very rare (Soini, 1988). This call is heard during situations that are highly frightening or disturbing (Soini, 1988). All individuals emit this vocalization (Soini, 1988). This call functions to communicate alarm or rage and is motivated by intense alarm and/or rage (Soini, 1988).

fear call: This call is ultrasonic and is emitted with the mouth wide open (Soini, 1988). This call is very rare (Soini, 1988). This call is heard during situations that are extremely fearful (Soini, 1988). All individuals emit this call (Soini, 1988). This call is motivated by extreme fear (Soini, 1988). In German this vocalization is called Hasslaut (Soini, 1988).

submissive trill: This is a high-pitched and soft, infantile trilling sounding call (Soini, 1988). This call has an uncommon frequency of utterance (Soini, 1988). This call is given by subordinates during agonistic interactions with more dominant individuals and by females during sexual chase (Soini, 1988). All individuals except for infants emit this vocalization (Soini, 1988). This call functions to communicate submission or appeasement and is motivate by mild fear (Soini, 1988). The response to this call is that the receiver may be appeased (Soini, 1988). In German this is called Demutlaut (Soini, 1988).

submissive squeal: This call is made up of infantile squealing (Soini, 1988). This call is uncommon (Soini, 1988). This call is heard during situations of begging or taking food from others, during rough play, and during agonistic interactions with more dominant individuals (Soini, 1988). This call is emitted by juveniles and subordinates (Soini, 1988). This call functions to communicate submission or appeasement and is motivate by mild fear (Soini, 1988). The response to this call is that the receiver may be appeased (Soini, 1988).

submissive call: This call is composed of a combination of whistle and trill notes, accompanied by tsik notes (Soini, 1988). This call is uncommon (Soini, 1988). This call is given by subordinates during agonistic interactions with more dominant individuals and by females during sexual chase (Soini, 1988). This call is emitted by juveniles, subordinates, and females (Soini, 1988). This call functions to communicate submission or appeasement and is motivate by mild fear (Soini, 1988). The response to this call is that the receiver may be appeased (Soini, 1988).

infant squeal: This is a series of harsh "nga" notes (Soini, 1988; Newman et al., 1987). This call is very common (Soini, 1988); although Newman et al. (1987) found this call to be infrequent, except when disturbed by human observers. This call is heard during situations of thwarted access to food or body contact (Soini, 1988). This call is heard by infants, including neonates (Soini, 1988). This call functions to signal distress and is motivated by distress (Soini, 1988). The response to this call is that access is granted to the infants (Soini, 1988). In German this is called Quarren (Soini, 1988).

tsik and phee call: This is infantile trilling and tsik notes, accompanied by squealing (Soini, 1988). This call is very common (Soini, 1988); although Newman et al. (1987) found this call to be infrequent, except when disturbed by human observers. This call is heard in situations of when infants are left alone or when denied access to food or body contact (Soini, 1988). This call functions to signal distress and is motivated by distress (Soini, 1988). The response to this call is that the infant may be retrieved (Soini, 1988). In German this is called Lautes Quarren und Zwitschern (Soini, 1988).

infant J-call: This is high-pitched trilling that ends with one long note (Soini, 1988; Newman et al., 1987). This call is very common (Soini, 1988). This call is heard infants that are over 15 days of age are left alone (Soini, 1988; Elowson et al., 1992). This call functions to achieve contact and is motivated by distress (Soini, 1988). In German this is called Trillerlaut (Soini, 1988).

infant trill: This call is composed of soft trilling notes, with having the mouth closed or partly open (Soini, 1988; Newman et al., 1987). This call has a common occurrence (Soini, 1988). This call is heard by infants over 3 weeks and juveniles when they are content or in calm situations (Soini, 1988). This call functions to achieve contact and is motivated by contentment (Soini, 1988). Infant trill changes over time as the infant pygmy marmoset ages (Snowdon and Elowson, 2001). In German this is called Leises Zirpen (Soini, 1988).

excitement squeals: This call is high-pitched and soft, composed of "wi" notes, accompanied by click notes (Soini, 1988). This call has a common occurrence (Soini, 1988). This is heard when an individual is stalking an insect (Soini, 1988). All individuals except for infants emit this call (Soini, 1988). This call is motivated by high, non-fearful excitement (Soini, 1988). Elowson et al., (1992) found that the duration of infant trill increased with age.

defecation call: This call is very common in captivity (Soini, 1988). This call is heard prior to defecation and is emitted by all individuals (Soini, 1988). The motivation for this call is defecation (Soini, 1988).

OLFACTORY COMMUNICATION: circumanal marking: This is when a pygmy marmoset rubs the substrate with the circumanal areas in a sitting position; this is the most frequent marking behavior for this species (Epple et al., 1993; Soini, 1988). All individuals perform circumanal marking (Soini, 1988). This behavior is motivated by mild arousal and functions as scent marking (Soini, 1988). This is also called sit rub (Soini, 1988). pull rub: This is when an individual will pull the body forward along a horizontal or sloping support, having the inguinal region pressed against the substrate (Soini, 1988). This behavior is less common than sit rub (Soini, 1988). This behavior is seen behavioral estrus and is performed by adults (Soini, 1988). This behavior functions to scent mark and is motivated by sexual arousal (Soini, 1988). The response to this is that the consort may mark the same spot (Soini, 1988).

sternal rub: This is when an individual pushes the body forward along a horizontal support, having the sternum and cheek pressed against the substrate (Soini, 1988). This behavior has a rare occurrence (Soini, 1988). This behavior is seen during situations of rejected sexual approach and frustration (Soini, 1988). Adult males will perform this behavior (Soini, 1988). This functions as a scent mark and for relief and is motivate by frustration (Soini, 1988).

VISUAL COMMUNICATION:
genital presenting: This is when a pygmy marmoset would have the anal region turned towards the receiver, and raise the tail so that the genitalia are showing (Soini, 1987). This behavior occurs commonly during behavioral estrus (Soini, 1988). This behavior is performed only by females in estrus (Soini, 1988). The function of this behavior is to synchronize mating and has a sexual motivation (Soini, 1988). The male will respond by sniffing and licking the exposed vulva (Soini, 1988). This is the only callitrichid species that performs genital presenting (Kinzey, 1997).

genital display: This is when the anogenital region is presented to a recipient by raising the tail, with having the back arched and the pelage ruffled (Soini, 1988). This behavior has a common occurrence (Soini, 1988). This behavior is seen in situations of intraspecies agonistic interactions (Soini, 1988). This behavior is performed by adults and subadults, and in juveniles this behavior occurs incipiently (Soini, 1988). This is a threat display given to intruders to their area or sometimes given by dominant males to subordinate males (Soini, 1987). This is also performed by the female when she does not to be copulated by a male (Soini, 1987). This behavior functions to signal social and territorial dominance and is motivated by agonistic tendencies (Soini, 1988). The response to this behavior is often submissive signals (Soini, 1988).

consort walking: This a slow type of locomotion, much like an "insect-stalk," where the male follows the female 1-3 meters behind, mimicking all of her movements (Soini, 1988). This behavior is common during behavioral estrus (Soini, 1988). This behavior is seen during behavioral estrus and is performed by the consort pair (male and female couple) (Soini, 1988). This behavior functions to strengthen the pair bond and has a sexual motivation (Soini, 1988).

teeth baring: This is where an individual has the mouth open and the lips retracted, with the upper canines partially bared (Soini, 1988). This display rarely occurs (Soini, 1988). This is performed by adults and is used in highly threatening interactions with other species (Soini, 1988). The function of this is to communicate threat and is motivated by fear (Soini, 1988).

open mouth: This is when the mouth is partly open, without the lips being retracted (Soini, 1988). This display commonly occurs (Soini, 1988). This occurs when an individual is presented with a new or mildly frightening situation (Soini, 1988). This behavioral pattern is performed by infants and juveniles (Soini, 1988). The function of this is to communicate threat and is motivated by mild fear (Soini, 1988).

stare: This is when an individual will stare with intensity at a conspecific (Soini, 1988). This behavior rarely occurs (Soini, 1988). This display is seen during agonistic social interactions (Soini, 1988). Males will also increase their performance of stare when the female consort is in ovulation (Converse et al., 1995). The function of this behavior is to communicate threat and is motivated by agonistic tendencies (Soini, 1988). The response to this display is usually submissive signals (Soini, 1988).

frown: This is when the eyebrows are lowered and the pelage is ruffled (Soini, 1988). This display has a common occurrence (Soini, 1988). This behavior is seen during agonistic interactions (Soini, 1988). All members perform this behavior (Soini, 1988). The function of this display is to communicate threat and is motivated by aggression (Soini, 1988).

scare face: This is when the eyebrows and ears are pulled back, accompanied by pilo-smoothing (Soini, 1988). This behavior has a common occurrence (Soini, 1988). This behavioral pattern occurs during frightening situations (Soini, 1988). All members perform this behavior (Soini, 1988). The function of this behavior is to appease and is motivated by fear (Soini, 1988).

tongue flicking: This is when the tongue of the pygmy marmoset is vibrated between lips, which are partially opened in the vertical plane. An audible lapping sound occurs during the performance of this behavior (Soini, 1988). This noise is made by the dominant male during mating. This display can also occur during sexual chase and play, and is also performed by subadult males (Soini, 1988). The function of this display is for mating solicitation and is motivated by sexual arousal (Soini, 1988).

quick tongue protrusion: This is when the tongue is protruded rhythmically, and is often mixed with tongue flicking (Soini, 1988). This behavior has a common occurrence (Soini, 1988). This behavior occurs during sexual play and while mounting (Soini, 1988). This behavioral pattern is performed by adult males (Soini, 1988). The function of this behavior is to appease and has a friendly motivation (Soini, 1988).

slow tongue protrusion: This is when the tongue tip is protruded slowly, with the mouth being half closed (Soini, 1988). This behavior is not common (Soini, 1988). This behavior is performed in the presence of an observer (Soini, 1988). All members of the group, except infants, perform this behavior (Soini, 1988). This behavior is motivated by mild disturbance or fear (Soini, 1988).

defense-threat stance: This is when an individual is in a stance with the back arched and having lowered hindquarters, and accompanied by ruffle and teeth baring (Soini, 1988). This behavior rarely occurs (Soini, 1988). This behavior is seen in situations of interspecies and intraspecies confrontations (Soini, 1988). This behavior is performed by adults (Soini, 1988). The function of this behavior is intimidation, to facilitate an attack or escape, and is motivated by conflict (Soini, 1988).

submission posture: This is when the body is crouched or flattened against the substrate and is accompanied by pilo-smoothing (Soini, 1988). This behavior rarely occurs (Soini, 1988). This behavior is seen in situations where a subordinate is involved in highly agonistic interactions with a more dominant individual (Soini, 1988). This behavior is performed by adults and subadults of both sexes (Soini, 1988). The function of this behavior is to appease and is motivated by fear (Soini, 1988). This behavior serves to thwart further aggression by the dominant towards the subordinate (Soini, 1988).

head tilting: This is a slow, side-to-side tilting of the head while watching (Soini, 1988). This is a common behavior (Soini, 1988). This behavior is seen during encounters with odd or potentially dangerous animals (Soini, 1988). This behavior is performed by all individuals (all age classes and sexes) (Soini, 1988). This behavior is motivated by alarm and the function may be optical (Soini, 1988).

swaying: This is a jerky, side-to-side swaying of the body (Soini, 1988). This behavior has a common occurrence (Soini, 1988). This behavior is seen in situations of mobbing and play (Soini, 1988). All individuals perform this behavior (Soini, 1988). This behavioral pattern functions to attract the attention of companions and is motivated by excitement and alarm (Soini, 1988).

present back or flank: This is when an individual lies down in front of another and offers the back of the flank (Soini, 1988). This behavior is very common (Soini, 1988). This behavior is seen during resting and is performed by all individuals (Soini, 1988). This behavior serves to solicit grooming and is motivated by the desire to be groomed (Soini, 1988). The response to this is grooming (Soini, 1988).

displacement scratching: This is an inattentive and vigorous scratching of the thighs and/or arms (Soini, 1988). This behavior is found to be common in the presence of an observer (human) (Soini, 1988). This behavior is seen in the presence of the observer or another disturbing stimulus and is performed by all individuals (Soini, 1988). The function of this behavior may be relief and is motivated by mild disturbance (Soini, 1988).

tail-wagging: This is when an individual wags the tail laterally or circularly in a spasmodic and rapid motion, with the tail being stiff and in full piloerection (Soini, 1988). This is a very common behavior (Soini, 1988). This is seen during frustrating situations and is performed by infants and juveniles (Soini, 1988). The motivation for this behavior is stress (Soini, 1988).

ruffle: This is when there are varying degrees of erection of the pelage of the head, body, and tail (Soini, 1988). This is a very common behavior (Soini, 1988). This is seen during agonistic situations and is performed by all individuals (Soini, 1988). Males will also increase their performance of ruffle when the female consort is in ovulation (Converse et al., 1995). Adult females will perform ruffle more during the postpairing period as compared with the postpartum period (Carlson et al., 1996). This behavior functions to make the individual appear larger and more intimidating and has agonistic motivations (Soini, 1988). This behavior is also called piloerection.

pilo-smoothing: This is when an individual will smooth the pelage of the head and body (Soini, 1988). This behavior has a common occurrence (Soini, 1988). This is seen by the subordinate during agonistic interactions with a more dominant individual (Soini, 1988). This behavior is performed by all individuals except for infants (Soini, 1988). This behavior functions to appease and is motivated by fear (Soini, 1988).

TACTILE COMMUNICATION:
ano-genital licking: This behavior is done by the male after she performs genital presenting towards him (Soini, 1987). This behavior is seen during the time of female ovulation (heat) (Converse et al., 1995).

anogenital rub: This is when one individual rubs the anogenital region against another's body (Soini, 1988). This behavior is rare (Soini, 1988). This is seen by the estrus female when the adult male approaches her from behind (Soini, 1988). This functions as a scent mark and is motivate by sexual arousal (Soini, 1988). The response to this is that the receiver/recipient remains stationary (Soini, 1988).

huddle: This is when one individual will sit or lie down in close bodily contact with another (Soini, 1988). This behavior is very common (Soini, 1988). The situation for which this behavior occurs varies, but it is seen most intensely during behavioral estrus between consorting pairs (Soini, 1988). This behavior functions to strengthen the pair bond and has friendly motivations (Soini, 1988). The response is usually reciprocal behavior (Soini, 1988).

allogroom: This is when one individual will clean the pelage of another with the fingers and teeth (Soini, 1988). This behavior is very common (Soini, 1988). This is seen most often during rest and is performed by all individuals (Soini, 1988). This behavior functions to reinforce social cohesion and has friendly motivations (Soini, 1988). The response is often reciprocal behavior (Soini, 1988).

supplant butt: This is where a dominant individual will approach a subordinate from behind and butts it on the flank (Soini, 1988). This is a rare behavior (Soini, 1988). This is seen when a dominant individual will supplant a subordinate at an exudate hole (Soini, 1988). This functions to supplant and has agonistic motivations (Soini, 1988). The response is that the subordinate departs (Soini, 1988).

cuff: This is a violent tough or cuff against an opponent with a hand that is outstretched (Soini, 1988). This is a rare behavior (Soini, 1988). This is seen during highly agonistic intraspecies interactions (Soini, 1988). The dominant individual performs this behavior (Soini, 1988). This function to communicate a strong threat and has agonistic motivations (Soini, 1988). The response is that the recipient usually retreats (Soini, 1988).

REPRODUCTION:
The pygmy marmoset most often gives birth to twins, rarely singletons and triplets, with an interbirth interval of 5-7 months (Soini, 1993, 1988). There are peaks in birthing around the middle and the end of the year (Soini, 1988). However, Ziegler et al. (1990) found that there is no birth seasonality in captive pygmy marmosets. The gestation period for this species is 19 to 20 weeks (Christen, 1968, 1974; Soini, 1988). This species reaches sexual maturity at 15 to 18 months old (Soini, 1988; Carlson et al., 1997). This species has a two-week estrus cycle (Soini, 1988). In captivity it was found that daughters' sexual activity increased with the death of the mother, but the daughters ovulated normally while the mother was alive, suggesting behavioral reproductive suppression (Spurlock, 2002; Carlson et al., 1997).

Males begin to show sexual interest in females shortly after postpartum, and copulations that result in ejaculation tends to only occur during this time (Soini, 1988). Carlson et al., (1996) found that there are peaks in sexual behavior after pairing in the immediate periovulatory periods, possibly reflecting the creation of the pair bond. The dominant males tries to prevent other adult males from copulating with the dominant female, however, the possibility exists that other males are able to mount and copulate with the dominant (breeding) female (Soini, 1988). Before copulating, the dominant male and dominant female are seen to perform certain patterns such as: approaching and following the female by the male, chasing by the male, intensive smelling and licking of the female's genitalia and urine, genital presenting by the female, increase in scent-marking by both sexes, increase in time of huddling and grooming between the male and female (Soini, 1988; Carlson et al., 1996). Converse et al. (1995) in captive pygmy marmosets found that there was no increase in female scent marking or presenting when the female was ovulating. The male and female will engage in "consort walking," which a slow and deliberate walking having bent limbs along branches and lianas, with the female leading and the male following 0.5-1.5 meters behind imitating the female (Soini, 1987). Males during this time will cease insect stalking, instead stalking the female when she stalks insects (Soini, 1987). Males will also strut and tongue-flick towards the female during courtship (Soini, 1988). The female will respond to sniffing and mounting by the male with genital presenting, accompanied by chattering, and stiff arch tail raise (Soini, 1988). Males will then respond to this by intensive sniffing and licking of the female's vulva (Soini, 1988).

Sexual mounts by the male towards the female occurs as follows: the male will claps the waist of the female and mount her lower back, the male's feet will usually remain on the substrate, an copulations were short (a few seconds) consisting of quick thrusts that are followed by the quivering of the male's body (Soini, 1988). Post-coitus, the male will sometimes lick his penis, the female's vulva, and the female's face and entire body (Soini, 1988; Christen, 1974). After copulation is completed, the pair will either resume previous activity or huddle together and groom each other (Soini, 1988). Copulation mounts can occur at any time of the day and in any place (Soini, 1988).

Pygmy marmoset neonates have a body mass between 13 and 15 grams and a total length that ranges from 120 to 139 millimeters (Soini, 1988). The natal pelage coloration is described as lemon-yellow agouti on all parts except for the head, which is dark gray with yellow agouti ears, a yellow antiface, and light nasolateral stripes (Soini, 1988). Infant pelage color becomes more adult-like at the 5th to 6th months of life (Soini, 1988). All group members take part in caring for the young, with infants being constantly carried for the first two weeks (Soini, 1988; Wamboldt et al., 1988); although Queralt and Vea (1998) found that the father carries the infant the majority of the time from the start. After the first two weeks, infants are deposited in a protected place while the group forages and feeds (Soini, 1988). This place is generally in the crown of the tree in which the group is feeding (Soini, 1988). The adult male (the father) has been found to carry infants the most of the group members (Soini, 1988; Queralt and Vea, 1998; Queralt et al., 2001). Infants have been found to produce complex vocal bouts (babbling) 2-3 weeks after birth, which consist of on average 10 different call types out of 16 possible call types (Snowdon and Elowson, 2001). This babbling has also been found persist into the juvenile stage, with explanation being that babbling may increase social interactions, gain attention after the birth of a new infant, or be used by subordinates during competitive and agonistic interactions (Snowdon and Elowson, 2001). Infants are completely weaned by about the third month of life, but infants will start feeding off of exudate holes at about 6 weeks and feeding on insects from the parent's hands at 4 weeks (Soini, 1988). In captivity it has also been shown that food offering can occur between adults and infants (Feistner and Price, 1991).

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Last Updated: July 23, 2006.
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