Contrairement à d’autres groupes animaux, chez les primates, la hiérarchie de dominance ne détermine pas systématiquement le succès reproductif des mâles. Afin de comprendre pourquoi, j’ai étudié les stratégies de reproduction des mâles et des femelles dans un groupe de macaques rhésus de la population semi-libre de Cayo Santiago (Porto Rico), collectant des données comportementales, hormonales et génétiques pendant deux saisons de reproduction. Les résultats se résument en cinq points. 1. Les nouveaux mâles qui ont immigré dans le groupe d’étude occupaient tous les rangs les plus subordonnés de la hiérarchie de dominance et ont monté en rang suite au départ de mâles plus dominants. Ainsi, l’acquisition d’un rang supérieur s’est faite passivement, en absence de conflits. Par conséquent, les mâles dominants étaient généralement d’âge mature et avaient résidé plus longtemps dans le groupe que les mâles subordonnés. 2. L’accès des mâles aux femelles est en accord avec le « modèle de la priorité d’accès » selon lequel le nombre de femelles simultanément en œstrus détermine le rang de dominance du mâle le plus subordonné qui peut avoir accès à une femelle (p. ex. le mâle de rang 4 s’il y a quatre femelles en œstrus). Bien que les mâles dominants aient eu plus de partenaires et aient monopolisé les femelles de qualité supérieure (dominance, parité, âge) pendant leur période ovulatoire (identifiée grâce au profil hormonal de la progestérone), le rang de dominance n’a pas déterminé le succès reproductif, les mâles intermédiaires ayant engendré significativement plus de rejetons que prédit. Il est possible que ces jeunes adultes aient produit un éjaculat de meilleure qualité que les mâles dominants d’âge mature, leur donnant un avantage au niveau de la compétition spermatique. 3. Les mâles dominants préféraient les femelles dominantes, mais cette préférence n’était pas réciproque, ces femelles coopérant plutôt avec les mâles intermédiaires, plus jeunes et moins familiers (c.-à-d. courte durée de résidence). Au contraire, les femelles subordonnées ont coopéré avec les mâles dominants. La préférence des femelles pour les mâles non familiers pourrait être liée à l’attrait pour un nouveau bagage génétique. 4. L’intensité de la couleur de la peau du visage des femelles pendant le cycle ovarien était corrélée au moment de la phase ovulatoire, une information susceptible d’être utilisée par les mâles pour maximiser leur probabilité de fécondation. 5. Les femelles retiraient des bénéfices directs de leurs liaisons sexuelles. En effet, les femelles en liaison sexuelle bénéficiaient d’un niveau de tolérance plus élevé de la part de leur partenaire mâle lorsqu’elles étaient à proximité d’une source de nourriture défendable, comparativement aux autres femelles. En somme, bien que les mâles dominants aient bénéficié d’une priorité d’accès aux femelles fertiles, cela s’est avéré insuffisant pour leur garantir la fécondation de ces femelles parce que celles-ci avaient plusieurs partenaires sexuels. Il semble que l’âge et la durée de résidence des mâles, corrélats de leur mode d’acquisition du rang, aient confondu l’effet du rang de dominance. / In contrast to most animal groups, dominance hierarchy does not systematically determine male reproductive success in primates. In order to investigate why, I studied male and female reproductive strategies in a group of free-ranging rhesus macaques on Cayo Santiago, Puerto Rico. I collected behavioural, genetic, and hormonal data during two consecutive mating seasons. My results are summarized below. 1. All new males who immigrated into the study group occupied the lowest-ranking position in the dominance hierarchy and rose in rank as the higher-ranking males left the group. Achieving a higher dominance rank occurred passively, without physical conflict. Thus, dominant males were mature individuals who resided longest in the group. 2. Male access to oestrus females followed the predictions of the ‘priority of access’ model, in which the number of females in oestrus determines the rank of the lowest-ranking male who can access a female (e.g. the fourth ranking male if four females are in oestrus). Even though dominant males obtained more mating partners and monopolised higher quality females (dominance, parity, age) during the ovulation window (as identified using progesterone profiles), dominance rank did not determine reproductive success, as intermediate-ranking males sired significantly more infants than predicted. It is likely that those young, intermediate-ranking adult males produced high quality ejaculate, giving them an advantage in sperm competition. 3. Dominant males preferred high-ranking females, but this preference was not reciprocal; high-ranking females cooperated with younger and less familiar intermediate-ranking males. Conversely, subordinate females cooperated with dominant males. Female preference for non-familiar males (i.e. short residency in the group) may be explained by an attraction to a novel genetic pool. 4. Female facial color intensity during the ovarian cycle was correlated with the timing of the ovulation window. This information may be used by males in order to maximize their fertilisation probability. 5. Consort females enjoyed a higher level of tolerance from their male partner when they were in proximity to a monopolisable food source, compared to other, non-consort females. This suggests that females obtained direct benefits from their sexual consorts. In conclusion, even though dominant males had priority access to ovulating females in the group, this was insufficient to guarantee fertilisation when females had several sexual partners. It appears that males’ age and length of residency, both correlates of their rank acquisition mode, may have been confounding factors in dominance rank.

No description available.

Contrairement à d’autres groupes animaux, chez les primates, la hiérarchie de dominance ne détermine pas systématiquement le succès reproductif des mâles. Afin de comprendre pourquoi, j’ai étudié les stratégies de reproduction des mâles et des femelles dans un groupe de macaques rhésus de la population semi-libre de Cayo Santiago (Porto Rico), collectant des données comportementales, hormonales et génétiques pendant deux saisons de reproduction. Les résultats se résument en cinq points. 1. Les nouveaux mâles qui ont immigré dans le groupe d’étude occupaient tous les rangs les plus subordonnés de la hiérarchie de dominance et ont monté en rang suite au départ de mâles plus dominants. Ainsi, l’acquisition d’un rang supérieur s’est faite passivement, en absence de conflits. Par conséquent, les mâles dominants étaient généralement d’âge mature et avaient résidé plus longtemps dans le groupe que les mâles subordonnés. 2. L’accès des mâles aux femelles est en accord avec le « modèle de la priorité d’accès » selon lequel le nombre de femelles simultanément en œstrus détermine le rang de dominance du mâle le plus subordonné qui peut avoir accès à une femelle (p. ex. le mâle de rang 4 s’il y a quatre femelles en œstrus). Bien que les mâles dominants aient eu plus de partenaires et aient monopolisé les femelles de qualité supérieure (dominance, parité, âge) pendant leur période ovulatoire (identifiée grâce au profil hormonal de la progestérone), le rang de dominance n’a pas déterminé le succès reproductif, les mâles intermédiaires ayant engendré significativement plus de rejetons que prédit. Il est possible que ces jeunes adultes aient produit un éjaculat de meilleure qualité que les mâles dominants d’âge mature, leur donnant un avantage au niveau de la compétition spermatique. 3. Les mâles dominants préféraient les femelles dominantes, mais cette préférence n’était pas réciproque, ces femelles coopérant plutôt avec les mâles intermédiaires, plus jeunes et moins familiers (c.-à-d. courte durée de résidence). Au contraire, les femelles subordonnées ont coopéré avec les mâles dominants. La préférence des femelles pour les mâles non familiers pourrait être liée à l’attrait pour un nouveau bagage génétique. 4. L’intensité de la couleur de la peau du visage des femelles pendant le cycle ovarien était corrélée au moment de la phase ovulatoire, une information susceptible d’être utilisée par les mâles pour maximiser leur probabilité de fécondation. 5. Les femelles retiraient des bénéfices directs de leurs liaisons sexuelles. En effet, les femelles en liaison sexuelle bénéficiaient d’un niveau de tolérance plus élevé de la part de leur partenaire mâle lorsqu’elles étaient à proximité d’une source de nourriture défendable, comparativement aux autres femelles. En somme, bien que les mâles dominants aient bénéficié d’une priorité d’accès aux femelles fertiles, cela s’est avéré insuffisant pour leur garantir la fécondation de ces femelles parce que celles-ci avaient plusieurs partenaires sexuels. Il semble que l’âge et la durée de résidence des mâles, corrélats de leur mode d’acquisition du rang, aient confondu l’effet du rang de dominance. / In contrast to most animal groups, dominance hierarchy does not systematically determine male reproductive success in primates. In order to investigate why, I studied male and female reproductive strategies in a group of free-ranging rhesus macaques on Cayo Santiago, Puerto Rico. I collected behavioural, genetic, and hormonal data during two consecutive mating seasons. My results are summarized below. 1. All new males who immigrated into the study group occupied the lowest-ranking position in the dominance hierarchy and rose in rank as the higher-ranking males left the group. Achieving a higher dominance rank occurred passively, without physical conflict. Thus, dominant males were mature individuals who resided longest in the group. 2. Male access to oestrus females followed the predictions of the ‘priority of access’ model, in which the number of females in oestrus determines the rank of the lowest-ranking male who can access a female (e.g. the fourth ranking male if four females are in oestrus). Even though dominant males obtained more mating partners and monopolised higher quality females (dominance, parity, age) during the ovulation window (as identified using progesterone profiles), dominance rank did not determine reproductive success, as intermediate-ranking males sired significantly more infants than predicted. It is likely that those young, intermediate-ranking adult males produced high quality ejaculate, giving them an advantage in sperm competition. 3. Dominant males preferred high-ranking females, but this preference was not reciprocal; high-ranking females cooperated with younger and less familiar intermediate-ranking males. Conversely, subordinate females cooperated with dominant males. Female preference for non-familiar males (i.e. short residency in the group) may be explained by an attraction to a novel genetic pool. 4. Female facial color intensity during the ovarian cycle was correlated with the timing of the ovulation window. This information may be used by males in order to maximize their fertilisation probability. 5. Consort females enjoyed a higher level of tolerance from their male partner when they were in proximity to a monopolisable food source, compared to other, non-consort females. This suggests that females obtained direct benefits from their sexual consorts. In conclusion, even though dominant males had priority access to ovulating females in the group, this was insufficient to guarantee fertilisation when females had several sexual partners. It appears that males’ age and length of residency, both correlates of their rank acquisition mode, may have been confounding factors in dominance rank.

The entorhinal cortex (EC) in the medial temporal lobe plays a critical role in memory formation and is implicated in several neurological diseases including temporal lobe epilepsy and Alzheimer’s disease. Despite the known importance of this brain region, little is known about the normal bioelectrical activity patterns of the EC in awake, behaving primates. In order to develop effective therapies for diseases affecting the EC, we must first understand its normal properties. To contribute to our understanding of the EC, I monitored the activity of individual neurons and populations of neurons in the EC of rhesus macaque monkeys during free-viewing of photographs using electrophysiological techniques. The results of these experiments help to explain how primates can form memories of, and navigate through, the visual world. These experiments revealed neurons in the EC that represent visual space with triangular grid receptive fields and other neurons that prefer to fire near image borders. These properties are similar to those previously described in the rodent EC, but here the neuronal responses relate to viewing of remote space as opposed to representing the physical location of the animal. The representation of visual space may be aided by another EC neuron type that was discovered, free-viewing saccade direction cells, neurons that signaled the direction of upcoming saccades. Such a signal could be used by other cells to prepare to fire according to the future gaze location. Many of these spatially-responsive neurons also represented memory for images, suggesting that they may be useful for associating items with their locations. I also examined the neuronal circuitry of recognition memory for visual stimuli in the EC, and I found that population synchronization within the gamma-band (30-140 Hz) in superficial layers of the EC was modulated by stimulus novelty, while the strength of memory formation modulated gamma-band synchronization in the deep layers and in layer III. Furthermore, the strength of connectivity in the gamma-band between different layers was correlated with the strength of memory formation, with deep to superficial power transfer being correlated with stronger memory formation and superficial to deep transfer correlated with weaker memory formation. These findings support several previous investigations of hippocampal-entorhinal connectivity in the rodent and advance our understanding of the functional circuitry of the medial temporal lobe memory system. Finally, I explored the design of a device that could be used to investigate properties of brain tissue in vitro, potentially aiding in the development of treatments for disorders of the EC and other brain structures. We designed, fabricated, and validated a novel device for long-term maintenance of thick brain slices and 3-dimensional dissociated cell cultures on a perforated multi-electrode array. To date, most electrical recordings of thick tissue preparations have been performed by manually inserting electrode arrays. This work demonstrates a simple and effective solution to this problem by building a culture perfusion chamber around a planar perforated multi-electrode array. By making use of interstitial perfusion, the device maintained the thickness of tissue constructs and improved cellular survival as demonstrated by increased firing rates of perfused slices and 3-D cultures, compared to unperfused controls. To the best of our knowledge, this is the first thick tissue culture device to combine forced interstitial perfusion for long-term tissue maintenance and an integrated multi-electrode array for electrical recording and stimulation.

This research address the problem of inferring, through Radio-Frequency Identification (RFID) tracking data, the graph structures underlying social interactions in a group of rhesus macaques (a species of monkey). These social interactions are considered as independent affiliative and dominative components and are characterized by a variety of visual and auditory displays and gestures. Social structure in a group is an important indicator of its members’ relative level of access to resources and has interesting implications for an individual’s health. Automatic inference of the social structure in an animal group enables a number of important capabilities, including: 1. A verifiable measure of how the social structure is affected by an intervention such as a change in the environment, or the introduction of another animal, and 2. A potentially significant reduction in person hours normally used for assessing these changes. The behaviors of interest in the context of this research are those definable using the macaques’ spatial (x,y,z) position and motion inside an enclosure. Periods of time spent in close proximity with other group members are considered to be events of passive interaction and are used in the calculation of an Affiliation Matrix. This represents the strength of undirected interaction or tie-strength between individual animals. Dominance is a directed relation that is quantified using a heuristic for the detection of withdrawal and displacement behaviors. The results of an analysis based on these approaches for a group of 6 male monkeys that were tracked over a period of 60 days at the Yerkes Primate Research Center are presented in this Thesis.

No description available.

No description available.

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No description available.