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Local variations in fruit- and leaf-eating have been reported for some primate species; however, similar variations in exudate-feeding of pygmy marmosets, one of the most specialized neotropical primate species, have not been studied. In our 3-year study of four populations of pygmy marmosets in northeastern Ecuador, we characterized their exudate-feeding behavior by describing the use of exudate sources. We tested whether the use of exudate species was related to ecological factors such as the availability of exudate species in an area. We estimated the daily activity budgets of the groups with 1-hr scan samples and found significant interpopulation differences in the time spent on exudate feeding. We recorded a total of 18 exudate species used in the four populations; however, the populations differed in the total number of species used and in the preferred species. The most commonly used plant species were Sterculia apetala at San Pablo, Cedrela odorata at Sacha, Inga marginata at Amazoonico, and Parkia balslevii at Zancudo. We recorded the presence and abundance of the 18 exudate species in 90-m transects in the home range of each group and in one additional control area that contained no marmosets, for each population. Differences in the most-used exudate species among populations did not appear to be related to the availability of these species in each population, i.e., the marmosets did not use at random the exudate species available within their range, nor did they use more often the exudate species that were more abundant in their home ranges. One implication of our results for conservation is that protecting exudate resources based on data from only one area will not be sufficient to preserve pygmy marmosets in all populations. Am. J. Primatol. 66:145–158, 2005. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

By retrospective review of colony records and determinations of urinary hormones we have described the reproductive profile of the female pygmy marmoset (Cebuella pygmaea). The pygmy marmoset is a non seasonal breeder and gives birth to twins 76% of the time with single births occurring 16% and triplet births 8% of the time. Interbirth intervals ranged from 149-746 days. First births occurred to females between 24-42 months of age and 5-27 months post pairing. We measured urinary estrone, estradiol and estrone conjugates along with immunoreactive luteinizing hormone/chorionic gonadotropin (LH/CG). The postpartum LH peak occurred a mean of 15.6 days following parturition. The conception rate was 69% following the postpartum ovulation. Levels of CG rose a mean of 19 days following the LH peak in conceptive cycles and remained elevated for a mean of 76 days. Gestational length was a mean of 141.9 days from the LH peak to parturition. Only one female of the five studied displayed ovarian cycles which were a mean of 27 days in Length. Estradiol was the predominant urinary estrogen, however both estrone and estradiol were excreted in extremely high concentrations. LH peaks were discrete with urinary estrogens increasing at the time of the LH peak and remaining elevated throughout the luteal phase of the cycle. [ABSTRACT FROM AUTHOR]

This study examined changes in the behavioral and hormonal patterns of cooperatively breeding pairs in a primate species with the passing of time and with specific reproductive events. We (1) compared patterns of sexual, agonistic, and affiliative behavior of newly paired pygmy marmosets with the same behavioral patterns immediately after the birth of their first set of infants; (2) determined if postpartum behavioral differences existed between pairs whose infants lived and those whose infants died; and (3) examined whether behavioral patterns changed over the course of ovarian cycles in parous pygmy marmosets as had been documented in nulliparous pairs. The behavior of pairs was recorded during daily half-hour focal samples for 60 days after pairing, and 30 or 60 days after the birth of infants for pairs whose litters died or lived, respectively. Daily urine samples from females during the study were analyzed for luteinizing hormone and pregnanediol glucuronide concentrations to determine dates of ovulation. The results indicated that males consistently altered their sexual behavior and olfactory monitoring of mates during periovulatory periods in the females' cycles both postpairing and postpartum, while similar rates of social and sexual behavior were maintained between the conditions. Sexual behavior occurred throughout the females' ovarian cycles. Peaks in sexual behavior during the periovulatory period in nulliparous pairs disappeared after the birth of infants. Pairs whose infants died showed higher rates of sexual behavior than pairs with surviving infants. Social and sexual behavior may function to maintain the relationship both during and outside of ovulation, especially with the loss of infants. © 1996 Wiley-Liss, Inc., (Copyright © 1996 Wiley‐Liss, Inc.)

Pygmy marmosets (Cebuella pygmaea) use a variety of trill-like vocalizations to maintain contact among group members throughout the day. Frequently, when one animal gives a trill, other animals will respond antiphonally. Among three pygmy marmosets in a captive group, there were clear patterns or sequences of calling among animals. All three animals would call in sequence more frequently than expected by chance, while the likelihood of an animal calling twice before each of the other animals called once was less than expected by chance. One particular ordering of three individuals calling in sequence was more common than the other ordering of three animals. Individual differences were found between the likelihood of initiating call sequences and the likelihood of calling later in a sequence. Pygmy marmosets appear to have a conversational rule system to govern their antiphonal calling., (Copyright © 1984 Wiley-Liss, Inc., A Wiley Company.)

Only a few nonhuman species (chimpanzees and orangutans) have displayed mirror-image recognition of themselves by grooming at a spot that can only be seen with the mirror. Pygmy marmosets have never been observed to self-groom, but they do behave toward mirrors in a manner suggestive of the early stages of mirror-image recognition. They displayed a rapid extinction of social threat responses to their own image and of novelty responses to mirrors, but continued to show mirror-specific responses such as following their own image, playing peek-a-boo, and looking at their image throughout a 28-day period of mirror exposure. The pygmy marmosets used a mirror to locate otherwise unseen conspecifics from other groups and directed threat responses toward the real location of these animals rather than to their mirror-image. Pygmy marmosets displayed the precursor behaviors to mirror-image recognition., (Copyright © 1983 Wiley‐Liss, Inc., A Wiley Company.)