Determinants of Paternity Success in a Group of Captive Vervet Monkeys ( Chlorocebus aethiops sabaeus )

Paternity success of high-ranking primate males is affected by the number of males and the number of fertile females and their cycle synchrony. Female vervets in the wild show strong reproductive seasonality and do not advertise the ovulatory period with conspicuous signals or behavior. Because this makes it difficult for males to monopolize fertile females, it can be expected that male reproductive skew in this species is lower than in other cercopithecines living in multimale groups that advertise the ovulatory period. We assessed male reproductive success in a captive vervet group, initially consisting of 4 males and 12 unrelated females. Besides a general low reproductive skew, we predicted paternity success of the alpha males to be dependent on the overlap of synchronously fertile females, month into alpha male tenure, and housing conditions (the subjects were kept in a large park but had to be locked in a small indoor compartment during the winter months). Further, because the number of males reaching their prime increased over time, we predicted a decrease in reproductive success of the alpha male with increasing tenure length of the alpha male. To assess this we collected genetic samples from 27 of 32 offspring born into the group during 3yr, using 7 polymorphic human microsatellite markers. Contrary to our predictions, reproductive success of the males occupying the alpha position during the study was among the highest found in cercopithecines, with the alpha males siring 78% of all offspring. The degree of overlapping fertile periods did not affect paternity success, nor did paternity success of the alpha male differ between the 2 housing conditions. Only the alpha male's tenure length had an effect. Alpha male reproductive success decreased over time, which we attribute to either a shift in female mate choice toward younger males or to increased competition among the males in the later stage of the alpha male's tenure. This study demonstrates the importance of assessing reproductive success of males throughout >1 season and should spawn more research into the role of female choice and postcopulatory mechanisms in this specie

The Effect of Fission-Fusion Zoo Housing on Hormonal and Behavioral Indicators of Stress in Bornean Orangutans ( Pongo pygmaeus )

The welfare of captive animals could be improved if zoos were to place more emphasis on their species-specific needs. In the wild, orangutans live in a fission-fusion social system and have a semisolitary lifestyle. However, most zoos keep orangutans in permanent groups, which may be stressful for them. Apenheul Primate Park in Apeldoorn, Netherlands, houses 14 Bornean orangutans in a simulated fission-fusion social system. To assess how this housing system affects indicators of stress, we measured fecal glucocorticoid metabolites (fGCM) and determined proportions of self-directed behavior (scratching and autogrooming). We compared fGCM concentrations of the Apenheul animals to those of zoo orangutans kept in permanent groups. In addition, we tested the effect of group size, visitor number, sex, age, and change of group composition on fGCM concentrations and proportions of self-directed behavior in the Apenheul orangutans. In contrast to Bornean orangutans housed in permanent groups, we did not find a group size effect on fGCM or on self-directed behavior in Apenheul's fission-fusion housing system. In addition, fGCM concentrations in Apenheul orangutans increased significantly with visitor numbers. Visitor number also affected proportions of self-directed behavior, and mean proportions of scratching were positively correlated with mean values of fGCM concentrations. Although these results suggest that the fission-fusion housing system in Apenheul reduces the group size effect leading to social stress in Bornean orangutans, they also show that visitors are an important factor that needs to be mitigated if the well-being of captive primates and other zoo animals is to be improved

The cost of associating with males for Bornean and Sumatran female orangutans: a hidden form of sexual conflict?

Sexual coercion, in the form of forced copulations, is relatively frequently observed in orangutans and generally attributed to their semi-solitary lifestyle. High ecological costs of association for females may be responsible for this lifestyle and may have prevented the evolution of morphological fertility indicators (e.g., sexual swellings), which would attract (male) associates. Therefore, sexual conflict may arise not only about mating per se but also about associations, because males may benefit from associations with females to monitor their reproductive state and attempt to monopolize their sexual activities. Here, we evaluate association patterns and costs for females when associating with both males and females of two different orangutan species at two study sites: Suaq, Sumatra (Pongo abelii), and Tuanan, Borneo (Pongo pygmaeus wurmbii). Female association frequency with both males and females was higher in the Sumatran population, living in more productive habitat. Accordingly, we found that the cost of association, in terms of reduced feeding to moving ratio and increased time being active, is higher in the less sociable Bornean population. Males generally initiated and maintained such costly associations with females, and prolonged associations with males led to increased female fecal cortisol metabolite (FCM) levels at Tuanan, the Bornean population. We conclude that male-maintained associations are an expression of sexual conflict in orangutans, at least at Tuanan. For females, this cost of association may be responsible for the lack of sexual signaling, while needing to confuse paternity. Significance statement: Socioecological theory predicts a trade-off between the benefits of sociality and the ecological costs of increased feeding competition. Orangutans' semi-solitary lifestyle has been attributed to the combination of high association costs and low predation risk. Previous work revealed a positive correlation between association frequencies and habitat productivity, but did not measure the costs of association. In this comparative study, we show that females likely incur costs from involuntary, male-maintained associations, especially when they last for several days and particularly in the population characterized by lower association frequencies. Association maintenance therefore qualifies as another expression of sexual conflict in orangutans, and especially prolonged, male-maintained associations may qualify as an indirect form of sexual coercion

Species-specific patterns in fecal glucocorticoid and androgen levels in zoo-living orangutans (Pongo spp.)

In contrast to most primate species, including the other great apes, orangutans maintain a fission–fusion social system in the wild without being part of a stable community. In zoos, however, they are kept in permanent groups, usually consisting of one adult male and several females. In zoo orangutans, we predict higher levels of glucocorticoids and androgens in the Bornean species compared to its congener from Sumatra, due to the much more solitary lifestyle of Bornean orangutans and the apparent higher frequency of male aggression directed towards females in this species in the wild. To compare hormone levels of the two orangutan species, we validated a fecal glucocorticoid and a fecal androgen assay. Subsequently, fecal samples from a total of 73 female and 38 male orangutans housed in 29 European zoos were analyzed to investigate the effect of species, social group size, age and (for female glucocorticoid levels) reproductive state and the presence of adult males on fecal hormone metabolite concentrations. The results of linear mixed effect models indicate that both male and female Bornean orangutans show a steeper increase in glucocorticoid levels with increasing group size than Sumatran orangutans. We therefore conclude that Sumatran zoo orangutans are better able to adjust to social housing conditions than their Bornean congeners. In addition, our analyses reveal higher glucocorticoid levels in lactating females of both species compared to non-lactating and juvenile females. Concerning androgen levels in males, our analyses revealed significantly higher concentrations in Bornean than Sumatran orangutans. These differences in both glucocorticoid and androgen output between the two species of orangutan are presumably linked to ecological and behavioral differences and could possibly be attributed to phenotypic plasticity. However, given that we found interspecific differences in hormone excretion in captivity, where both species live under very similar conditions, we conclude that this variation has a genetic basis

Determinants of paternity success in a group of captive vervet monkeys (Chlorocebus aethiops sabaeus)

Paternity success of high-ranking primate males is affected by the number of males and the number of fertile females and their cycle synchrony. Female vervets in the wild show strong reproductive seasonality and do not advertise the ovulatory period with conspicuous signals or behavior. Because this makes it difficult for males to monopolize fertile females, it can be expected that male reproductive skew in this species is lower than in other cercopithecines living in multimale groups that advertise the ovulatory period. We assessed male reproductive success in a captive vervet group, initially consisting of 4 males and 12 unrelated females. Besides a general low reproductive skew, we predicted paternity success of the alpha males to be dependent on the overlap of synchronously fertile females, month into alpha male tenure, and housing conditions (the subjects were kept in a large park but had to be locked in a small indoor compartment during the winter months). Further, because the number of males reaching their prime increased over time, we predicted a decrease in reproductive success of the alpha male with increasing tenure length of the alpha male

The effect of fission–fusion zoo housing on hormonal and behavioral indicators of stress in Bornean Orangutans (Pongo pygmaeus)

The welfare of captive animals could be improved if zoos were to place more emphasis on their species-specific needs. In the wild, orangutans live in a fission–fusion social system and have a semisolitary lifestyle. However, most zoos keep orangutans in permanent groups, which may be stressful for them. Apenheul Primate Park in Apeldoorn, Netherlands, houses 14 Bornean orangutans in a simulated fission–fusion social system. To assess how this housing system affects indicators of stress, we measured fecal glucocorticoid metabolites (fGCM) and determined proportions of self-directed behavior (scratching and autogrooming). We compared fGCM concentrations of the Apenheul animals to those of zoo orangutans kept in permanent groups. In addition, we tested the effect of group size, visitor number, sex, age, and change of group composition on fGCM concentrations and proportions of self-directed behavior in the Apenheul orangutans. In contrast to Bornean orangutans housed in permanent groups, we did not find a group size effect on fGCM or on self-directed behavior in Apenheul’s fission–fusion housing system. In addition, fGCM concentrations in Apenheul orangutans increased significantly with visitor numbers. Visitor number also affected proportions of self-directed behavior, and mean proportions of scratching were positively correlated with mean values of fGCM concentrations. Although these results suggest that the fission–fusion housing system in Apenheul reduces the group size effect leading to social stress in Bornean orangutans, they also show that visitors are an important factor that needs to be mitigated if the well-being of captive primates and other zoo animals is to be improved