Reproductive events of wild cotton-top tamarins (Saguinus oedipus) in Colombia

Proyecto Titi: Teaching children that cotton‐top tamarins ( Saguinus oedipus ) are not appropriate pets

Cotton-top tamarins (Saguinus oedipus) are a critically endangered species found only in Colombia. Their survival is threatened by extensive habitat destruction and the illegal pet trade. Because many people in Colombia have a low level of awareness of cotton-top tamarins and even less understanding of the impacts that the illegal pet trade has on the species and its long-term survival, Proyecto Tití has developed a series of programs for children in rural elementary schools that introduce children to cotton-top tamarins. This study examines Proyecto Titi's efforts to reduce the desire to have a cotton-top tamarin as a pet with outcomes focused specifically on (1) creating an emotional connection between people and cotton-top tamarins, (2) identifying the feelings and understanding the challenges that cotton-top tamarin face when they are kept as pets, and (3) empowering students to make positive choices to help cotton-top tamarins. Both TITI KIDS and TITIRITIANDO programs helped students to (1) increase their knowledge of cotton-top tamarins, (2) understand the damage that the pet trade has on individual animals and the long-term survival of cotton-top tamarins and (3) provide practical actions that they can engage in to protect cotton-top tamarins for the future. Our hope is that students from our programs become advocates for conservation in their communities and assist in the long-term conservation activities to protect cotton-top tamarins in Colombia.

Factors influencing the survival of wild cotton-top tamarin (Saguinus oedipus) infants

Studies of cooperative breeding species have suggested that helpers are needed for infant survival and that helpers gain skills to successfully raise their own offspring. Studies of callitrichids in managed care and early field studies suggested that group size correlated with infant survival and that helpers needed to learn parental skills to be successful breeders. We present infant survival data from a 20-year field study of cotton-top tamarins (Saguinus oedipus) in Colombia involving 126 litters born to 41 females. There was no difference in the survival of male and female offspring to 6 months of age. However, litter size impacted survival, with triplet litters having lower survival and male triplets having lower survival than females. Loss of infants was highest in the first week of life and, of the animals remaining in the group at 6 months of age, 90% of them survived to 1 year. The mean length of time in the natal group was 2.3 years but some young migrated to other groups after 4 months of age. Group size and number of male helpers (>1 year) was not related to infant survival. However, groups with only one male had fewer surviving infants. Primiparous females had lower infant survival, but previous infant care experience by mothers as helpers had no effect on survival. A major cause of infant loss was group disruption due to deaths/evictions/loss of the reproductively active animals, or immigration of pregnant females. Thus, factors that cause a change in the stability of the reproductively active animals can disrupt group cohesion. Capture of individuals for the illegal pet trade, as well as habitat fragmentation, may increase competition between groups for access to territories and breeding opportunities. This may have long-term impacts to infant survival in this critically endangered species.

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

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

Reproductive seasonality in primates: patterns, concepts and unsolved questions

Primates, like other mammals, exhibit an annual reproductive pattern that ranges from strictly seasonal breeding to giving birth in all months of the year, but factors mediating this variation are not fully understood. We applied both a categorical description and quantitative measures of the birth peak breadth based on daily observations in zoos to characterise reproductive seasonality in 141 primate species with an average of 941 birth events per species. Absolute day length at the beginning of the mating season in seasonally reproducing species was not correlated between populations from natural habitats and zoos. The mid-point of latitudinal range was a major factor associated with reproductive seasonality, indicating a correlation with photoperiod. Gestation length, annual mean temperature, natural diet and Malagasy origin were other important factors associated with reproductive seasonality. Birth seasons were shorter with increasing latitude of geographical origin, corresponding to the decreasing length of the favourable season. Species with longer gestation periods were less seasonal than species with shorter ones, possibly because shorter gestation periods more easily facilitate the synchronisation of reproductive activity with annual cycles. Habitat conditions with higher mean annual temperature were also linked to less-seasonal reproduction, independently of the latitude effect. Species with a high percentage of leaves in their natural diet were generally non-seasonal, potentially because the availability of mature leaves is comparatively independent of seasons. Malagasy primates were more seasonal in their births than species from other regions. This might be due to the low resting metabolism of Malagasy primates, the comparatively high degree of temporal predictability of Malagasy ecosystems, or historical constraints peculiar to Malagasy primates. Latitudinal range showed a weaker but also significant association with reproductive seasonality. Amongst species with seasonal reproduction in their natural habitats, smaller primate species were more likely than larger species to shift to non-seasonal breeding in captivity. The percentage of species that changed their breeding pattern in zoos was higher in primates (30%) than in previous studies on Carnivora and Ruminantia (13 and 10%, respectively), reflecting a higher concentration of primate species in the tropics. When comparing only species that showed seasonal reproduction in natural habitats at absolute latitudes ≤11.75°, primates did not differ significantly from these two other taxa in the proportion of species that changed to a less-seasonal pattern in zoos. However, in this latitude range, natural populations of primates and Carnivora had a significantly higher proportion of seasonally reproducing species than Ruminantia, suggesting that in spite of their generally more flexible diets, both primates and Carnivora are more exposed to resource fluctuation than ruminants.

The evolution of pair-living, sexual monogamy, and cooperative infant care: Insights from research on wild owl monkeys, titis, sakis, and tamarins

"Monogamy" and pair bonding have long been of interest to anthropologists and primatologists. Their study contributes to our knowledge of human evolutionary biology and social evolution without the cultural trappings associated with studying human societies directly. Here, we first provide an overview of theoretical considerations, followed by an evaluation of recent comparative studies of the evolution of "social monogamy"; we are left with serious doubts about the conclusions of these studies that stem from the often poor quality of the data used and an overreliance on secondary sources without vetting the data therein. We then describe our field research program on four "monogamous" platyrrhines (owl monkeys, titis, sakis, and tamarins), evaluate how well our data support various hypotheses proposed to explain "monogamy," and compare our data to those reported on the same genera in comparative studies. Overall, we found a distressing lack of agreement between the data used in comparative studies and data from the literature for the taxa that we work with. In the final section, we propose areas of research that deserve more attention. We stress the need for more high-quality natural history data, and we urge researchers to be cautious about the uncritical use of variables of uncertain internal validity. Overall, it is imperative that biological anthropologists establish and follow clear criteria for comparing and combining results from published studies and that researchers, reviewers, and editors alike comply with these standards to improve the transparency, reproducibility, and interpretability of causal inferences made in comparative studies.

Balancing contest competition, scramble competition, and social tolerance at feeding sites in wild common marmosets (Callithrix jacchus)

Models of primate sociality focus on the costs and benefits of group living and how factors such as rank, feeding competition, alliance formation, and cooperative behavior shape within-group social relationships. We conducted a series of controlled field experiments designed to investigate how resource distribution (one or three of four reward platforms) and amount of food on a reward platform affected foraging strategies and individual feeding success in four groups of wild common marmosets (Callithrix jacchus) living in the Caatinga of northeastern Brazil. At our field site, common marmoset groups are characterized by a single breeding female who can produce twin litters twice per year, strong social cohesion, and cooperative infant care provided principally by several adult male helpers. We found that except for the dominant breeding female, rank (based on aggression) was not a strong predictor of feeding success. Although the breeding female in each group occupied the highest rank position and obtained the greatest daily feeding success, all other group members, including adults and juveniles experienced relatively equal feeding success across most experimental conditions. This was accomplished using a balance of behavioral strategies related to contest competition, scramble competition (associated with a finder's advantage), and social tolerance (sharing the same feeding platform). Based on these results, the social structure of common marmosets is best described as "single female dominance," with the breeding female maximizing food intake needed to offset the energetic costs associated with reproductive twinning and the ability to produce two litters per year. Cooperative infant caregiving, in which the number of helpers is positively correlated with offspring survivorship, requires a set of behavioral strategies that serve to reduce contest competition and promote prosocial behaviors at feeding sites.

Hormonal correlates of development and natal dispersal in wild female owl monkeys (Aotus azarae) of Argentina

Pair-living and socially monogamous primates typically do not reproduce before dispersing. It is currently unclear whether this reproductive suppression is due to endocrine or behavioral mechanisms. Cooperatively breeding taxa, like callitrichids, may forego reproduction in natal groups because they reap inclusive fitness benefits and/or they are avoiding inbreeding. However, neither of these benefits of delayed reproduction appear to adequately explain the lack of reproduction prior to leaving the natal group in pair-living monogamous species. In this study, we determined whether wild Azara's owl monkeys (Aotus azarae) in the Argentinean Chaco establish reproductive maturity prior to dispersing. We utilized 635 fecal extracts to characterize reproductive hormone profiles of 11 wild juvenile and subadult females using enzyme immunoassays. Subadult females showed hormone profiles indicative of ovulatory cycling and had mean PdG and E1G concentrations approximately five times higher than juveniles. Contrary to expectations from the inbreeding avoidance hypothesis, female owl monkeys do not delay puberty, but rather commence ovarian cycling while residing in their natal group. Still, subadults appear to have a period during which they experience irregular, non-conceptive cycles prior to reproducing. Commencing these irregular cycles in the natal group may allow them to develop a state of suspended readiness, which could be essential to securing a mate, while avoiding costs of ranging solitarily. Our results indicate that reproductive suppression in female owl monkeys is not due to endocrine suppression. We suggest that adults likely use behavioral mechanisms to prevent subadults from reproducing with unrelated adult males in their natal group.

An Assessment of the Population of Cotton-Top Tamarins (Saguinus oedipus) and Their Habitat in Colombia

Numerous animals have declining populations due to habitat loss, illegal wildlife trade, and climate change. The cotton-top tamarin (Saguinus oedipus) is a Critically Endangered primate species, endemic to northwest Colombia, threatened by deforestation and illegal trade. In order to assess the current state of this species, we analyzed changes in the population of cotton-top tamarins and its habitat from 2005 to 2012. We used a tailor-made "lure strip transect" method to survey 43 accessible forest parcels that represent 30% of the species' range. Estimated population size in the surveyed region was approximately 2,050 in 2005 and 1,900 in 2012, with a coefficient of variation of approximately 10%. The estimated population change between surveys was -7% (a decline of approximately 1.3% per year) suggesting a relatively stable population. If densities of inaccessible forest parcels are similar to those of surveyed samples, the estimated population of cotton-top tamarins in the wild in 2012 was 6,946 individuals. We also recorded little change in the amount of suitable habitat for cotton-top tamarins between sample periods: in 2005, 18% of surveyed forest was preferred habitat for cotton-top tamarins, while in 2012, 17% percent was preferred. We attribute the relatively stable population of this Critically Endangered species to increased conservation efforts of Proyecto Tití, conservation NGOs, and the Colombian government. Due to continued threats to cotton-top tamarins and their habitat such as agriculture and urban expansion, ongoing conservation efforts are needed to ensure the long-term survival of cotton-top tamarins in Colombia.

The development of small primate models for aging research

Nonhuman primate (NHP) aging research has traditionally relied mainly on the rhesus macaque. But the long lifespan, low reproductive rate, and relatively large body size of macaques and related Old World monkeys make them less than ideal models for aging research. Manifold advantages would attend the use of smaller, more rapidly developing, shorter-lived NHP species in aging studies, not the least of which are lower cost and the ability to do shorter research projects. Arbitrarily defining "small" primates as those weighing less than 500 g, we assess small, relatively short-lived species among the prosimians and callitrichids for suitability as models for human aging research. Using the criteria of availability, knowledge about (and ease of) maintenance, the possibility of genetic manipulation (a hallmark of 21st century biology), and similarities to humans in the physiology of age-related changes, we suggest three species--two prosimians (Microcebus murinus and Galago senegalensis) and one New World monkey (Callithrix jacchus)--that deserve scrutiny for development as major NHP models for aging studies. We discuss one other New World monkey group, Cebus spp., that might also be an effective NHP model of aging as these species are longer-lived for their body size than any primate except humans.

Primatology comes of age: 2002 AAPA Luncheon address

The growth of primate field studies has occurred along multiple dimensions representing expansion in the number of species studied, comparative studies of different populations of the same species, and populations and groups studied over time. The accumulation of data on a broader taxonomic diversity of primates has contributed to advances in the use of comparative methods for gaining insights into interspecific variation in behavior patterns, but the incorporation of intraspecific variation into comparative models of behavior has lagged behind. This delay can be attributed, in part, to the slow rate at which the interacting effects of life history and demography on behavior emerge in slow-growing, long-lived primates. It may also reflect the anthropocentric foundation of field primatology, which historically focused on interspecific comparisons with humans instead of interpopulation variation among primates. Conservation concerns have stimulated new thinking about the importance of populations and the range of behavioral variation that populations maintain. The integration of intra- and interspecific behavioral variation will distinguish the next generation of comparative models in primatology, and set a new agenda as field primatology comes of age.

Stability of Breeding and Non-Breeding Groups of Golden-Headed Lion Tamarins (Leontopithecus Chrysomelas)

In Callitrichid primates, offspring remain in their natal group beyond the age of sexual maturity, increasing the group's inclusive fitness by cooperatively rearing their siblings. Contraception of the dominant female in these groups may alter the associated costs and benefits of this cooperative rearing in such a way that offspring themselves attempt to breed when a period longer than the normal inter-birth interval of one year has elapsed. Contraception of the dominant female may also induce changes in socio-sexual interactions between group members, which can lead to increased aggression after a short period. In this study, we investigated the occurrence of aggression in 16 captive groups of golden-headed lion tamarins (Leontopithecus chrysomelas) under three conditions: 1) no contraception used; 2) contraception used and offspring younger than one year present within the group; and 3) contraception used and all offspring in the group older than one year. We found that the probability of aggression occurring in the groups was best predicted by logistic regression models containing the factors ‘group size ‘ and ‘overall proportion of males ‘ or ‘number of sons ‘. Aggression was more likely in larger groups with a high proportion of males or a large number of sons. This effect was significantly stronger for groups in which all offspring were older than one year. Absence of dispersal opportunities and differences in male and female reproductive strategies may explain the observed patterns. The increased instability of large non-breeding groups presents a problem when using long-term contraceptive methods and should be taken into account when making decisions on the most suitable population-control procedures.

Are subordinates always stressed? A comparative analysis of rank differences in cortisol levels among primates

Among primate species there is pronounced variation in the relationship between social status and measures of stress physiology. An informal meta-analysis was designed to investigate the basis of this diversity across different primate societies. Species were included only if a substantial amount of published information was available regarding both social behavior and rank-related differences in stress physiology. Four Old World and three New World species met these criteria, including societies varying from small-group, singular cooperative breeders (common marmoset and cotton top tamarin) to large-troop, multi-male, multi-female polygynous mating systems (rhesus, cynomolgus, talapoin, squirrel monkeys, and olive baboon). A questionnaire was formulated to obtain information necessary to characterize the stress milieu for individuals in particular primate societies. We standardized cortisol values within each species by calculating the ratio of basal cortisol concentrations of subordinates to those of dominants in stable dominance hierarchies and expressing the ratio as a percentage (relative cortisol levels). The meta-analysis identified two variables that significantly predicted relative cortisol levels: subordinates exhibited higher relative cortisol levels when they (1). were subjected to higher rates of stressors, and (2). experienced decreased opportunities for social (including close kin) support. These findings have important implications for understanding the different physiological consequences of dominant and subordinate social status across primate societies and how social rank may differ in its behavioral and physiological manifestations among primate societies.

Parent-daughter relationships and social controls on fertility in female common marmosets, Callithrix jacchus

This study examined the reproductive status of mothers and daughters to determine if parent-eldest daughter interactions would influence the daughter's fertility in the cooperatively breeding common marmoset, Callithrix jacchus. Twice weekly fecal samples were collected for hormonal analyses from seven daughters and their mothers and analyzed for cortisol, estradiol, and progesterone by EIA. Behavioral data were collected three times weekly while the daughters were under three conditions: natal family, after removing from the family and paring with a novel male, and after removing from the paired condition and placed back with the family (renatal). Under the natal condition, five of the seven daughters exhibited ovarian cycles while their mother was pregnant or displaying ovarian cycling. The five cycling daughters spent significantly more time initiating affilative behaviors with their mothers than with their fathers and showed significant changes in their behavior over the length of the ovarian cycle. However, aggression, submission, and sexual behaviors were very low for daughters in the natal phase. No differences between cortisol levels were found for a daughter and her mother. Cortisol levels showed a significant and sustained increase upon pairing within the first 20 days. All females but one cycled while paired. Six of the seven females were accepted back into the family after pairing and five of the seven females were ovulating. These results suggest that marmoset daughters are not necessarily reproductively suppressed while living with the family. Additionally, these data suggest that female marmosets that leave their family to explore mating opportunities with other groups may return to their family without reproductive or aggressive consequences.

Excretion and measurement of estradiol and progesterone metabolites in the feces and urine of female squirrel monkeys (Saimiri sciureus)

The first objective of the present study was to determine the metabolic form and rate of excretion of ovarian hormone metabolites in the urine and feces of female squirrel monkeys injected with radiolabeled progesterone (Po) and estradiol. The major portion of the urinary metabolites of both hormones was excreted within 16-24 hr post-injection. Estrogen and Po isotopes in feces exhibited an excretion peak at 16 hr post-injection. The majority of recovered radiolabel of both hormones was excreted in feces. Chromatographic separation of fecal extractions indicated that the major estrogen metabolites in feces are in the free as opposed to the conjugated form. The radioactivity and immunoreactivity for estrone and estradiol (E(1) and E(2), respectively) in eluates of fecal samples subjected to celite co-chromatography indicated that both free E(1) and E(2) exist as excretion products in the feces of female squirrel monkeys. The major radioactive peaks for Po metabolites showed peaks in the elution profile at or very near the Po standard, and corresponded with the celite co-chromatography elution profile of Po standard when subjected to enzyme immunoassay (EIA). The second objective was to validate the application of EIA systems to measure fecal metabolites. Reproductive events of one female squirrel monkey across one annual reproductive cycle are described using the endocrine profile generated from fecal steroid assays. Examination of this profile confirmed that longitudinal fecal sampling and steroid hormone metabolite measurement in feces was not only feasible and practical, but accurately detected known reproductive events as well.

Why do cotton-top tamarin female helpers carry infants? A preliminary study

Shortly after giving birth, cotton-top tamarin mothers frequently attack the eldest female helpers [Snowdon et al., American Journal of Primatology 31:11-21, 1993]. Sometimes this aggression leads to the eviction of the eldest daughters from their natal groups 3-4 months after the birth of infants [Price & McGrew, Folia Primatologica 57:16-27, 1991]. We propose that daughters, during the act of carrying infants, may receive less aggression from mothers than when they are not carrying. On the other hand, given that mothers benefit from having others carry their infants, overall aggression received by female helpers from their mothers might be lower in those female helpers with a larger relative contribution to this activity. Four groups were observed during the first 9 weeks following the birth of infants, and aggression received was recorded for symmetrical as well as nonsymmetrical interactions. We found a positive correlation between contribution to infant carrying of female helpers and the overall aggression received from their mothers. Furthermore, the two eldest daughters with highest values of carrying contribution were evicted from their natal groups 3-4 months after the birth of infants. Although mothers do not appear to be more tolerant of female helpers that contribute the most to infant carrying, daughters do benefit from reduced aggression during the act of carrying, and remain in their natal group during the time period when infants must be carried.

Costs of Caregiving: Weight Loss in Captive Adult Male Cotton-Top Tamarins (Saguinus oedipus) Following the Birth of Infants

We examined changes in weight for 10 captive adult male cotton-top tamarins (Saguinus oedipus) from before the birth of infants through the first 16 weeks of infant life. Compared to before birth, males weighed significantly less in Weeks 1-4, 5-8, and 9-12 following the birth. Weights in Weeks 13-16 did not differ significantly from prebirth weights. Maximum weight loss for individual males ranged from 1.3 to 10.8% of prebirth body weight. Males in groups with fewer helpers lost significantly more weight than ones in groups with more helpers. For the 3 males that had no helper other than their mates, weight loss was particularly striking, ranging from 10.0 to 10.8% of their prebirth body weight. These results suggest that caring for infants is energetically costly, and that in this cooperatively breeding species, the presence of more individuals to share the burden of infant carrying reduces the cost to individual caregivers.

Measurement of urinary and fecal steroid metabolites during the ovarian cycle in captive and wild Japanese macaques, Macaca fuscata

We measured the concentration of steroid hormones from urine, feces, and blood samples of two captive Japanese macaques, Macaca fuscata, during nonconceptive ovarian cycles to compare the patterns of the excreted steroids with those of circulating steroids. Urine and feces were analyzed for estrone conjugates (E1C) and pregnanediol-3-glucronide (PdG) using enzyme immunoassays (EIAs), while plasma was analyzed for estradiol-17beta(E2), progesterone (P), and luteinizing hormone (LH) using radioimmunoassays (RIAs). Urinary and fecal E1C and PdG levels were approximately parallel to plasma E2 and P levels, respectively. The E1C profiles of daily urinary and fecal samples revealed a midcycle peak, followed by a sustained PdG increase lasting up to two weeks from the E1C peak. A fecal E1C peak was one day later than the urinary E1C peak. One of the captive females exhibited a discrete plasma LH peak, one indicator that ovulation has occurred, on the day following the urinary E1C peak, i.e., the same day of fecal E1C peak. We measured excreted steroids in nine wild females and determined the timing of ovulation by comparing fecal steroid profiles to those obtained in captive monkeys. Data from wild females indicated that eight of nine females conceived during their first ovulatory cycle of the sampling period, whereas the remaining female failed to conceive during the sampling period even though she ovulated. In the eight females that conceived, E1C increased again following the detected or estimated E1C peak, with levels comparable to the preovulatory peak levels, and sustained elevations of PdG for over 40 days. These data illustrate that the urinary and fecal profiles of ovarian steroid excretion obtained through the application of these noninvasive techniques provide an accurate approach for monitoring conceptive and nonconceptive ovarian cycle in captive and free-living Japanese macaques.

Costs of infant-carrying in the cotton-top tamarin (Saguinus oedipus)

Infant-carrying behavior among callitrichids seems to be a costly activity. Costs have been related to the physical efforts of carrying the weight of very heavy infants and to the resulting reduction in foraging efficiency. However, the costs of carrying in terms of the physical consequences for carriers have not previously been assessed. In this study, we have regarded weight loss in infant carriers as a measure of costs. We studied five families of cotton-top tamarins (Saguinus oedipus) during the first 9 weeks following the birth of infants. Captive-breeding conditions were required so that body weight could be measured frequently. To avoid inflicting undue stress on the subject animals, we used a noninvasive method for weighing the tamarins. Differences in carrying contribution were found amongst fathers and male and female helpers, with female helpers contributing less. We have found that carrying infants in the cotton-top tamarins is an activity that produces a weight loss. Fathers and male helpers go through a maximal body weight loss. While carrying, the tamarins also decrease food intake. However, no relationship was found between contribution to carrying and feeding time or in energetic intake during feeding observations. Thus, it seems that a direct relation doesn't exist between the observations of feeding and weight loss. Fathers increase their contribution to carrying during mothers' periovulatory periods. In this period, male helpers and especially fathers go through a maximal body weight loss. We found body weight losses of up to 11.3% in one subadult male and 9.1% in a father during the fifth week. No changes occurred in food intake in fathers or other male helpers during this period. During periovulatory periods, mothers carried less frequently but did increase their food intake. They gained weight from the second week after birth onward, especially during the periovulatory period. It seems that the infant-carrying behavior of fathers and male helpers may contribute to the improvement of the mothers' physical condition after birth and therefore may support a consecutive pregnancy.