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The ecological constraints hypothesis states that as group size increases, groups travel further and occupy larger home ranges in order to meet basic energetic needs for survival and reproduction. In this paper we used 19 years of demographic and ranging data on a study population of golden lion tamarins, Leontopithecus rosalia , to examine this hypothesis. Significant variation in rate of predation on lion tamarins during the study affected group size, membership and population density, which allowed us to test for predicted correlations between these changes and home range size. We found that predation-mediated changes in group composition and population density explained 71% of variation in home range size. Increased predation decreased lion tamarin home ranges because of the effects of decreased group size, fewer adult natal males and fewer reproductive females in the group. The effect of these factors on decreased ranging was offset somewhat by lower population density during high predation, which resulted in range expansion due to reduced pressure from neighbouring groups. We also found that groups with high future reproductive potential (i.e. with multiple breeding females) increased their range size. This effect was independent of group size. We propose a new hypothesis, that taxa with high rates of reproduction, such as lion tamarins, will increase home range size to accommodate future energy needs, rather than current needs, as would be predicted by the ecological constraints hypothesis. No or low production of infants and litters on the smallest lion tamarin ranges in our study supports this new hypothesis. [ABSTRACT FROM AUTHOR]

Parental investment theory predicts that natural selection will favour a parental ability to bias the offspring sex ratio in favour of that which will yield the highest benefit–cost payoff. The local resource enhancement hypothesis posits that in cooperative breeders, parents may favour offspring that will mitigate parental effort by helping to raise younger siblings. Conversely, the fragile male hypothesis suggests that parents will adjust the sex ratio in favour of the sex that experiences higher mortality. We examined international studbook data of two cooperatively breeding primate species with differing reproductive strategies: golden lion tamarins, Leontopithecus rosalia, which typically give birth to twins, and callimicos, Callimico goeldii, which almost always give birth to singletons. The tamarins showed a stronger secondary sex-ratio bias in favour of males than did the callimicos, as predicted by the local resource enhancement hypothesis, because tamarins sustain higher per-parturition costs and because sons may invest more effort in caring for their younger siblings than do daughters. However, a generalized linear regression failed to reveal factors that may influence this variation. There was no significant predictor of male bias based on mother's age, mother's number of previous parturitions or group size. Contrary to predictions of the fragile male hypothesis, sons were no less likely to survive the postnatal period of parental investment than were daughters. A greater understanding of this phenomenon is needed because the adult sex-ratio bias in favour of males has become so pronounced, especially in golden lion tamarins, as to cause management difficulties for the conservation of these endangered species. [ABSTRACT FROM AUTHOR]

Abstract: Across taxa, cooperative breeding has been associated with high reproductive skew. Cooperatively breeding golden lion tamarins (Leontopithecus rosalia) were long thought to have a monogynous mating system in which reproduction was limited to a single dominant female. Subordinates with few reproductive opportunities delayed dispersal and remained in the natal group to provide alloparental care to siblings, thus allowing dominant reproductive females to meet the energetic needs associated with high rates of reproduction and successful infant rearing. The goal of this study was to re-assess monogyny in wild golden lion tamarin groups based upon pregnancy diagnoses that used non-invasive enzyme immunoassay for progesterone and cortisol, combined with weekly data on individual weight gain, bi-annual physical examinations noting pregnancy and lactation status and daily behavioral observations. We established quantitative and qualitative criteria to detect and determine the timing of pregnancies that did not result in the birth of infants. Pregnancy polygyny occurred in 83% of golden lion tamarin groups studied. The loss of 64% of subordinate pregnancies compared to only 15% by dominant females limited reproductive success mainly to dominant females, thus maintaining high reproductive skew in female golden lion tamarins. Pregnancy loss by subordinate adults did not appear to result from dominant interference in subordinate hormonal mechanisms, but more likely resulted from subordinate abandonment of newborn infants to mitigate dominant aggression. [Copyright &y& Elsevier]

Abstract: This study examines factors affecting androgen and cortisol levels in wild, male golden lion tamarins (Leontopithecus rosalia). Golden lion tamarins are a cooperatively breeding species in which groups often contain two potentially breeding males. Brothers frequently emigrate together and develop a clear dominance hierarchy, but interactions between them are primarily affiliative. Duos in which the males are not related are less stable. In addition, reproductive skew theory predicts that dominant males will be less likely to share reproduction with related subordinates. As such, we predicted that both androgens and cortisol would be higher in subordinate males unrelated to the dominant male. We also predicted that androgens in breeding males would be higher during the mating season than the birth/infant care season, as per Wingfield''s “challenge hypothesis” (1990). Fecal samples were collected from 24 males in 14 social groups and assayed by enzyme immunoassay. Androgen levels were higher in breeding males during the mating season, thus supporting the challenge hypothesis. However, while subordinate males unrelated to the dominant male had significantly lower androgens than any other group, cortisol levels were not correspondingly higher. These results suggest that unrelated subordinate males show measurable reproductive suppression and may use strategies such as infantilization to avert aggression from dominant males. [Copyright &y& Elsevier]

Examines the variations in maternal care in cooperatively breeding mammal Leontopithecus rosalia. Need to perform infant care due to the necessity of lactation; Social factors in maternal care; Measurement of prenatal care through neonatal weight.

Studies the dominant/subordinate relationship between males in groups of golden lion tamarins. Monopoly of paternity by a single male in most groups; Survivorship and reproductive success; Male behavior in multi-male groups; Breeding opportunities; Behavior potential and evidence for monopolization of reproduction; Demographic conditions for monopolization.

Presents data on the demography and resource availability collected during a study of a wild population of golden lion tamarins in which monogyny is common and polygyny is rare. Relative reproductive success of females on monogynous and polygynous territories; Presentation of a cost-benefit model to explain evolution of polygyny in birds; Assumptions of the model.

Determines whether and what type of information is contained in the vocalizations uttered by the golden lion tamarins to twelve different foods. Significant preference differences; Correlation of vocalization rates with food preference scores for the foods; Significant vocalization difference; Discriminant function analysis.