The first set of question of the Junior Research Group is to expand our knowledge of paternity in some specific projects outline below.
1. Development of paternal kin bias
In this long-term study we are going to test the mechanisms underlying paternal kin discrimination. The most likely mechanisms are familiarity and phenotype matching. Most studies on paternal kin recognition suggested phenotype matching, but did not test for all sources of familiarity. We therefore follow individuals from birth till they reach adulthood to understand the development of paternal kin bias. We are testing whether the mothers and/or the father mediate familiarity among paternal half-siblings.
Male reproduction is skewed in most mammalian species, which means that few males share reproduction while the majority of males do not reproduce at all. To date most studies on reproductive skew are limited to one social group or few reproductive seasons, so we know little about male lifetime reproductive success and whether this shows a skewed distribution over male lifetime too. We are also interested to understand whether males have a limited time window of successful reproduction or whether longevity can add to fecundity. In this study we use 20 years of genetic data of the entire population to address these questions.
3. Male care and its potential impact on infant fitness
Here we investigate the influence of male care onto infants fitness suggested by previous studies by predicting that infants observed more often in affiliation with males/fathers or in longer co-residency with their sires should show fitness benefits in comparison to infants with less or no male/father affiliation or sire co-residency. The phenotypes predicted to vary with paternal care are weight, body fat and testicular volume. In addition we consider chance of infant survival and lifetime reproductive success as fitness aspects related to reproductive output.
4. Paternal care in Sulawesi black crested macaques
Female primates mate with multiple partners during likely conception to confuse paternity in order to minimize the risk of infanticide. Previous studies have demonstrated that male group members present at the time of the infants’ conception are less likely to attack infants than males immigrating after the infants’ conception. As males always face some uncertainty of paternity even when they mate-guarded a given female for most of her cycle, it is still not clear whether or not male primates are able to recognize their own offspring and if so, whether males provide paternal care. In Sulawesi black crested macaques mortality and/or injuries of newborns are frequent and injured newborns are protected by certain males. The aim of our project is to study male-offspring interaction in this species to understand whether males indeed provide paternal care to offspring during infanticide attacks and what mechanism males use to identify their offspring.
5. Male fitness: Achievement and maintenance of dominance in male Sulawesi black crested macaques
Males of high dominance status are known to sire more offspring than males of low dominance status. However, it is less studied how males achieve and maintain high rank. The aim of this study is to examine the determinants of a male’s position within a group’s dominance hierarchy in wild Sulawesi black crested macaques. This study will address the following questions:
Do individual features, such as age, kin availability, body condition, characteristics of sexual signals and/or personality affect a male’s dominance rank.
How important are male coalition partners for the achievement and maintenance of high dominance status.
How important is female support for the achievement and maintenance of high dominance status. Finally, how stable are male hierarchies in time.
Species/Field site: Sulawesi black crested macaques/ Tangkoko-Bataungus Nature Reserve, Indonesia
Which cues do primates use to identify their paternal kin?
The second aim of this Junior Research Group is to study potential cues which might be used by primates to identify their paternal kin.
1. Odor as a cue
If primates use odor to identify paternal kin, we would expect to find individual odor pattern persistent over time. Furthermore, individual odor pattern are expected to show higher similarity (or smaller variations) between paternal kin than between non-kin. To show that primates use odor to identify paternal kin, we will investigate whether monkeys give a differential behavioral response when being exposed to kin or non-kin odor (Bioassay test).
When animals use appearance as a cue to assess paternal kinship in others, we predict that paternal kin share more visual cues than unrelated individuals. To test this hypothesis we collected high quality standardized images of individuals of known kinship. As a control, we collected images of non-kin whom we matched for age and sex. Use of human assessors offers the quickest and most cost-effective method of gaining insight into whether reliable facial cues exist. Human subjects will be tested using an automated procedure, in which stimuli are displayed on a color computer monitor and responses indicated via the keyboard. Alternatively, we are looking for face recognition software which would allow us to quantify facial similarities.
If animals use acoustic characteristics as a cue to assess paternal kinship, we would first need to demonstrate that paternal kin share more acoustic characteristics than unrelated individuals. If such patterns can be observed, we aim to test whether individuals indeed use vocal cues to recognize paternal kin. For example, we would predict that test subjects respond different to playback calls of paternal half-siblings than to playback calls of non-kin.
To examine whether personality is a cue used in paternal kin discrimination we asked current research assistants who are well acquainted with individual monkeys to assess the personality of the monkeys using newly developed personality inventories. We will compare correlations among the personality factors of pairs of paternal kin to unrelated pairs. While this is not a direct measure of heritability, it should show whether individuals who share a father are more like one another than those who do not.
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Buchan, J.C., Alberts, S.C., Silk, J.B., Altmann, J. (2003) True paternal care in a multi-male primate society. Nature 425: 179-181.
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Charpentier, M.J.E, Van Horn, R.C., Altmann, J., Alberts, S.C. (2008) Paternal effects on offspring fitness in a multimale primate society. Proceedings of the National Academy of Science U.S.A. 105: 1988-1992.
Silk, J.B., Altmann, J., Alberts, S.C. (2006) Social relationships among adult female baboons (Papio cynocephalus). I. Variation in the strength of social bonds. Behavioral Ecology and Sociobiology 61: 183-195.
Smith, K.L., Alberts, S.C., Altmann, J. (2003) Wild female baboons bias their social behaviour towards paternal half-sisters. Proceedings of the Royal Society of London, Series B 270: 503-510.
Van Horn, R.C., Buchan, J.C., Altmann, J., Alberts, S.C. (2007) Divided destinies: group choice by female savannah baboons during social group fission. Behavioral Ecology and Sociobiology 61: 1823-1837.
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Widdig, A., Bercovitch, F.B., Streich, W.J., Nürnberg, P., Krawczak, M. (2004) A longitudinal analysis of reproductive skew in male rhesus macaques. Proceedings of the Royal Society London B 271: 819-826.
Widdig, A., Nürnberg, P., Bercovitch, F.B., Trefilov, A., Berard, J.B., Kessler, M.J., Schmidtke, J., Streich, J.W., Krawczak, M. (2006) Consequences of group fission for the patterns of relatedness among rhesus macaques. Molecular Ecology 15: 3825-2832.
Widdig, A., Nürnberg, P., Krawczak, M., Streich, W.J., Bercovitch, F.B. (2001) Paternal relatedness and age proximity regulate social relationships among adult female rhesus macaques. Proceedings of the National Academy of Science U.S.A. 98: 13769-13773.
Widdig, A., Nürnberg, P., Krawczak, M., Streich, W.J., Bercovitch, F.B. (2002) Affiliation and aggression among adult female rhesus macaques: a genetic analysis of paternal cohorts. Behaviour 139: 371-391.
Widdig, A., Streich, W.J., Nürnberg, P., Croucher, P.J.P., Bercovitch, F.B., Krawczak, M. (2006) Paternal kin bias in the agonistic interventions of adult female rhesus macaques (Macaca mulatta). Behavioral Ecology and Sociobiology 61: 205-214.