Andreas Paul

Male care in primates: does it ever reflect paternity?

Female mammals have internal fertilization, long gestation, and lactation. These basic facts of reproductive biology have important social consequences. Internal fertilization (accompanied by sperm competition) forces males either to face considerable uncertainty about paternity or to invest heavily in mate guarding. Long gestation increases the benefits of mate desertion for males. And because only females lactate, males have relatively less to contribute to rearing the young. Hence, it is not surprising that male mammals rarely assist their mates in caring for their young: Direct infant care by males occurs in fewer than 5 percent of all mammalian species.1,2 In fact, many mammalian mothers attack males, even possible father of their offspring.3

The sociobiology of male-infant interactions in Barbary macaques, Macaca sylvanus

Abstract Unlike most Old World monkeys, male Barbary macaques frequently associate with and care for infants shortly after birth. Three functional hypotheses have been proposed to explain male–infant interactions in this and other species. (1) The ‘paternal investment hypothesis’ proposes that males invest in their own progeny or otherwise related infants, (2) the ‘mating effort hypothesis’ proposes males care for infants to increase their access to mothers, and (3) the ‘agonistic buffering hypothesis’ proposes that males use infants to regulate their relations with other males. These hypotheses were tested using data on male–infant interactions, paternity and sexual behaviour obtained during a longitudinal study on Barbary macaques living in a large outdoor enclosure. Paternity of 91 infants was determined by DNA fingerprinting. Hypothesis 1 was not supported, because males did not preferentially interact with closely related infants. Similarly, hypothesis 2 was not supported because male caretakers were not more likely to sire the next infant of the mother than non-caretakers. Hypothesis 3 was supported because (1) the direction of at least one type of triadic interactions was significantly biased towards higher-ranking males, (2) the patterning of triadic interactions was strongly dependent on the rank distance between the males, and (3) interaction frequency increased significantly during periods of high inter-male tension. While kin relations were unimportant, the use of infants familiar with the opponent suggests that males make use of their knowledge of relationships between other group members. Beyond agonistic buffering, triadic interactions may serve an important function in coalition formation.

Timing of Birth, Female Reproductive Success and Infant Sex Ratio in Semifree-Ranging Barbary Macaques (Macaca sylvanus)

Examined were 5 years of data on the reproduction of a semifree-ranging population of Barbary macaques (Macaca sylvanus). In this seasonally breeding species – birth season: mid-Mar

Sexual Selection and Mate Choice

After a long period of dormancy, Darwins theory of sexual selection in general, and mate choice in particular, now represents one of the most active fields in evolutionary research. After a brief overview of the history of ideas and a short introduction into the main mechanisms of sexual selection, I discuss some recent theoretical developments and empirical findings in the study of mate choice and review the various current models of mate choice, which can be grossly divided into adaptive models and nonadaptive models. I also examine whether available primate evidence supports various hypotheses concerning mate choice. Although primatologists were long aware that nonhuman primates have preferences for certain mating partners, until recently the functions and evolutionary consequences of their preferences remained obscure. Now there is growing evidence that mate choice decisions provide primates with important direct or indirect benefits. For example, several observations are consistent with the hypothesis that by direct or indirect mate choice female primates lower the risk of infanticide or enhance the chance of producing viable offspring. Nevertheless, there are also significant holes in our knowledge. How the male mandrill, one of Darwins famous examples, got his brightly colored face, is still unknown.

The association between rank, mating effort, and reproductive success in male Barbary macaques (Macaca sylvanus)

The association between social rank, mating effort, and reproductive success of male Barbary macaques (Macaca sylvanus) has been evaluated by longterm behavioral observations and subsequent paternity determination via oligonucleotide DNA fingerprinting in a large semifreeranging group. All offspring born between 1985 and 1988 that survived to at least 1 year of age (n=75) were available for paternity testing. The exclusion of all but one of the potential fathers from paternity was possible in 70 cases (93%). Mating activities were recorded using ad lib. and focal female sampling techniques. The analysis of male mating effort was restricted to the most likely days of conception. Male rank correlated significantly with male mating success in all four breeding seasons and with male reproductive success in three of the four seasons. Mating success and reproductive success also showed a significant correlation, with the exception of one breeding season, in which the proportion of males per fertilizable female was especially high. Poor mating success was almost always associated with poor reproductive success, while good mating success was less predictive for a males actual reproductive success. This was apparently a consequence of sperm competition, resulting from the promiscuous mating system. Male mating success is not necessarily an unreliable indicator for reproductive success, provided that sufficient sample sizes are available and that conception periods can be determined. Sperm competition and other factors may weaken the association, however.

Female Reproductive Characteristics in Semifree-Ranging Barbary Macaques (Macaca sylvanus L. 1758)

Mating activities in a group of 178 Barbary macaques were studied during the breeding season 1982/83. Copulations were observed between the middle of August and the end of March. More than 80% of all copulations were recorded from October to December. Number of estrous periods ranged from 1 to 5, most females (67%) had 2 estrous periods. Most females (87%) conceived during the first estrus. Postconceptional bleedings and 1 postconceptional estrus were observed regularly. Mean interval between the end of conceptional estrus and the end of postconceptional estrus was 28 days. Mean interval between the end of conceptional estrus and the onset of bleeding was 18.2 days. Conception rate was 79%. Conceptions occurred between the end of September and the middle of February. Most females (60%) conceived between the middle of November and the middle of December. Mean gestation length for a viable infant was 164.7 days. Consequences of the strong breeding seasonality are discussed.

Dominance, kinship and reproductive value in female Barbary macaques (Macaca sylvanus) at Affenberg Salem

SummaryIn the course of a long-term study on social organization of semi-free-ranging Barbary macaques (Macaca sylvanus) at Affenberg Salem, genealogical and cross-genealogical rank relations of adult and adolescent females in three social groups were studied. Female rank was highly dependent on maternal rank, but the process of rank acquisition was also affected by age/size differences between members of different families. Mother-daughter rank reversal was rare, but all old, postreproductive matriarchs were outranked by their adult daughters. Contrary to findings of other studies on macaques, younger sisters seldom outranked older sisters. There was no genealogy with a strict age-inversed hierarchy among adult sisters as described for rhesus and Japanese macaques. Rank reversals between sisters were more frequent in genealogies with old or dead matriarchs, in large clans, and in dyads with an age difference of more than 1 year, indicating that demographic variables influence intra-genealogical dominance relations. It is suggested that close, long-lasting relationships between sisters and mothers and doughters impede rank reversals. Previous evolutionary models of female dominance relations in primates that explain rank relations among sisters as a function of their reproductive value or as a strategy of the mother to maintain her own status are not supported by the data. The results of this and other studies indicate that rank reversal between sisters is not as universal for Old World monkeys, or even macaques, as frequently proposed.

KINSHIP, FAMILIARITY AND MATING AVOIDANCE IN BARBARY MACAQUES, MACACA SYLVANUS

Abstract Abstract. Long-term data on sexual behaviour in Barbary macaques revealed a strong mating inhibition between co-residing maternal relatives, and between those, mostly unrelated, males and females with a caretaking relationship during the females infancy. Sexual interactions were observed in only 15 out of 371 possible maternal dyads. There was a bias towards distant kin and towards dyads in which the male was older than the female. Sexual interactions were recorded in only two out of 14 former caretaking dyads with a strong relationship but in 10 out of 17 dyads with a weak and/or temporary relationship. Unfamiliar maternal relatives and paternal relatives showed no mating avoidance. Three out of four of these maternal dyads, and 67 out of 133 possible paternal dyads became incestuous. Paternity was determined by DNA-fingerprinting. Almost all paternal dyads became incestuous after more than 2 years of co-residence. Owing to high sexual activities outside the period of conception and the inability of related and unrelated males to monopolize access to fertile females, only two out of 62 potentially inbred infants were actually inbred via the paternal line. Establishment of a mating inhibition but also its absence in some individuals indicated that only familiarity during early life, regardless of genetic relatedness, was responsible for mutual sexual indifference. This mental mechanism of inbreeding avoidance is regarded as an important trigger for male natal migration.

Reproductive senescence and terminal investment in female Barbary macaques (Macaca sylvanus) at Salem

The reproductive history of 207 female Barbary macaques, living in a large outdoor enclosure in Southwest Germany, was studied during an 11-year period. The results yielded a significant relationship between female age and fecundity, with fertility rates lower than expected among young and old females. Analysis of the reproductive history of individual females revealed a significant decline in fertility from prime age (7–12 years) to mid age (13–19 years), and from mid age to old age (20–25 years). The proportion of long interbirth intervals increased steadily among aging females. Infant survival was not significantly related to maternal age, but offspring of old females showed the highest survivorship. Behavioral observations revealed that old mothers weaned their offspring significantly later than younger mothers, suggesting that prolongation of interbirth intervals is due not only to deteriorating physical condition but also to increased maternal investment, as life history theory predicts. Reproduction ceased during the middle of the third decade of life. Final cessation of estrous cycling invariably occurred 3 or 4 years after the birth of the last offspring, but a postreproductive life span of ≥5 years appears to be common in this population. Available data suggest that reproductive senescence and menopause are more common among nonhuman primates than widely believed and that both traits are part of an adaptive life history strategy.

Female-female competition and male mate choice in barbary macaques (Macaca sylvanus)

Due to a strong breeding synchronization, the Barbary macaque is a likely candidate for female competition for access to mates, female reproductive suppression, and male mate choice. The present study evaluated the significance of these factors for the mating system of this species. Female competition was analysed from focal observations of 19 out of 59 potentially reproductive females in their conception period. Ad libitum recorded sexual interactions of all animals were used for an analysis of male mate choice. The focal females were aggressive towards females once per 6.1 h and received aggression from females once per 3.8 h. However, they were three times more frequently the target of male aggression (once per 1.2 h), whereby the aggressor was often the momentary sexual partner. Rate of aggression received from males and females was not related with female rank. Females of all cycle stages disturbed sexual contacts, whereby the intruder was dominant to the target in most episodes (86 out of 100). Intruders more attractive than their targets were most successful in terminating the sexual association of their target, but success of intrusions was low and not related with female rank. The intruder copulated with the former partner of her target in only 5 intrusion episodes. Rate and date of conception and infant survival was not related with female rank, indicating that aggression against females during the conception period and intrusions into sexual contacts did not impair reproduction. Therefore, female