Malgré la multiplicité des études démontrant le comportement fascinant des animaux dans leur milieu naturel, quelques domaines de recherches demeurent difficiles à aborder. Ainsi, l’étude de certains aspects cognitifs nécessite un certain contrôle sur l’environnement afin de dissocier les influences écologiques et sociales de l’implication cognitive ; par exemple la cognition spatiale incluant la mémoire spatiale, les mécanismes d’orientation spatiale, ainsi que leur implication dans la navigation, tel que par la planification. L’étude de la cognition spatiale des chimpanzés sauvages s’est déroulée dans le Parc national de Taï, une forêt tropicale dense où les ressources potentielles sont abondantes et réparties sur un territoire de 25 km², avec une visibilité d’environ 30 mètres. De plus, les chimpanzés vivent dans une société du type fission-fusion, impliquant de multiples relations sociales. Toutefois, l’enregistrement précis de la position et des activités des chimpanzés, ainsi qu’une carte botanique précise, nous a permis de dissocier les effets écologiques, sociaux et cognitifs afin de mieux comprendre les relations entre ces différents facteurs. Par cette étude, nous montrons que les chimpanzés ont développé un mécanisme permettant une navigation précise grâce à une carte Euclidienne contenant des informations sur la direction et la distances vers des ressources connues. Ce mécanisme est extrêmement adapté et efficace par la connaissance précise de la localisation de milliers de ressources dans leur habitat. Ces capacités permettent d’augmenter leur efficacité en sélectionnant les ressources les plus productives, en les planifiant à l’avance et, de manière plus avancée, en planifiant le parcours le plus court à travers ces différentes ressources durant la journée lorsque la pression sociale requière une meilleure précision dans le choix des ressources. Ces découvertes illustrent d’abord les capacités extraordinaires des chimpanzés, et deuxièmement que les aspects cognitifs peuvent être expliqués dans le milieu naturel des animaux. / Whereas numerous studies demonstrated fascinating behaviour of animals in their natural habitat, some important areas of research were difficult to tackle in the field. This is the case of many studies on cognitive aspects that required controlled environment to dissociate ecological and social influence from cognition. One of these important areas of research is the spatial cognition including spatial memory, spatial orientation mechanisms and the practical use of these abilities to travel efficiently, such as planning skills. This study on spatial cognition in wild chimpanzees took place in Taï National Park, a tropical dense forest where potential food resources are highly abundant in their 25 km² territory, and the visibility is approximately 30 meters. Adding to this complexity, chimpanzees live in a fission-fusion society, maintaining relationships with each other. Nevertheless, with a precise recording of chimpanzee’s location and activities and a precise botanic map of the territory, we were able to dissociate the ecological, social and cognitive effects and understand some relationships between these factors. Here, we showed that wild chimpanzees developed a precise mechanism to navigate efficiently in their large area using a Euclidean map containing accurate information about direction and distance to the known resources. This mechanism is highly adapted and efficient as the chimpanzees have a precise knowledge of the resources location in their area, remembering the location of thousand trees location. These highly developed abilities allowed them to increase their efficiency by selecting the most productive resources, planning them in advanced and on a higher level to plan the shortest path through these major resources during the day when the social pressure induce a higher precision in resource selection. These findings highlight first the outstanding spatial abilities of wild chimpanzees and second that cognition can be better explained in animals’ natural complex environment. / Trotz zahlreicher Studien, die das faszinierende Verhalten von Wildtieren in ihrer natürlichen Umwelt dokumentieren, bleiben einige Studienfelder schwer erfassbar. So ist zum Beispiel bei der Erforschung von bestimmten kognitiven Aspekten die Rücksichtnahme auf den Umweltfaktor erforderlich, damit Umwelt- und Sozialeinfluss von den kognitiven Faktoren unterschieden werden können. Zu diesen Untersuchungsfeldern gehört die Raumkognition, welche das Raumgedächtnis, die Mechanismen der Raumorientierung sowie deren effizientes Nutzen durch die Schimpansen, z.B. durch ihre Fähigkeit zum Planen, einschließt. Die vorgestellte Studie über Raumkognition bei wild lebenden Schimpansen wurde im Nationalpark von Tai durchgeführt, das heißt, in einem dichten tropischen Wald, wo potentielle Ressourcen bei einer Sichtweite von ungefähr 30 Metern auf einem 25 qm großen Areal reichlich verteilt sind. Hinzu kommt, dass Schimpansen in einer Fission-Fusion Gesellschaftsstruktur leben, die vielfache soziale Beziehungen fördern. Jedoch, mit einer genauen Registrierung der räumlichen Lage und der Aktivitäten der Schimpansen und anhand einer präzisen botanischen Karte des Gebiets, konnten wir die Umwelt-, Sozial- und kognitiven Effekte gegeneinander abgrenzen und somit die zwischen diesen unterschiedlichen Faktoren bestehenden Beziehungen erfassen. In dieser Studie zeigen wir, dass Schimpansen einen besonderen Mechanismus zur Raumorientierung auf ihrem Gebiet entwickelt haben. Dabei verfügen sie über eine euklidische Mind-Karte mit präzisen Informationen über Richtungen und Entfernungen zu den bekannten Ressourcen. Durch ein genaues Wissen über die Verteilung der Nahrungsressourcen auf ihrem Gebiet ist dieser Mechanismus hoch effizient. Dank dieser Fähigkeiten werden Schimpansen immer effizienter, indem sie die ergiebigsten Ressourcen auswählen, dabei planende Fähigkeiten einsetzen und weiterhin indem sie an einem Tag die kürzeste Strecke zu den verschiedenen Ressourcen ausmachen, wenn der soziale Druck höchste Präzision in der Wahl der Nahrungsressourcen erfordert. Diese Erkenntnisse erhellen zuallererst die außergewöhnlichen Fähigkeiten der wild lebenden Schimpansen und beweisen, dass sich kognitive Mechanismen bei wild lebenden Tieren in ihrer natürlichen Umwelt besser erklären lassen.

Increasing anthropogenic alterations propelled by a growing human population paired with ecological perturbations and climate change has amplified rates of disease transmission at the human-wildlife interface. While attention has focused primarily on diseases that cause high rates of morbidity and mortality, there is a dearth of research on more common, non-lethal “mild” infections. However, despite less obvious and immediate consequences, these infections still have long-term effects on both public health and the conservation of wildlife. Currently, disease research is primarily cross-sectional, with a lack of longitudinal studies, leading to an undervaluation of the dynamic nature of disease systems. In addition to pathogen monitoring, concurrently being able to measure immune system activation will help to clarify the effects of non-lethal diseases on host health and to provide further insights into life-history trade-offs. Here, I investigated malaria parasite (Plasmodium spp.) infections, a “mild” disease, in wild habituated chimpanzees (Pan troglodytes verus) residing in Taï National Park (TNP), Côte d'Ivoire. I used historical biological samples collected from non-human primates (including chimpanzees) and humans, as well as collected mosquitoes within their habitat. First, I identified longitudinal patterns of malaria parasite prevalence detected in chimpanzee faeces; next, I validated a biomarker of immune system activation, urinary neopterin, in wild chimpanzees; and lastly, within a larger ecological framework, I examined the interface of malaria parasite transmission between humans and non-human primates sharing a habitat. With a longitudinal study design, I found substantial intra- and inter-annual fluctuations in the faecal detection of malaria parasites across four non-consecutive sampling periods between 2004 and 2015. Peaks were observed during wet seasons—suggesting that environmental factors relating to vector abundance determine infection patterns. A higher prevalence was also detected in younger individuals, suggesting that the availability of susceptible hosts plays a role. With variations in parasite detection, similar trends should also be observed in health status. Urinary neopterin, an early inflammation marker of the non-specific immune response, increases during malaria parasite infections in humans and has been validated as a marker of immune system activation in laboratory and captive non-human primates. However, it was unclear whether it would be sensitive enough to provide a clear signal in mild diseases against the back-drop of co-infections commonly seen in wildlife. Therefore, we first needed to validate urinary neopterin as a biomarker of immune system activation during severe disease in wild animals. I measured urinary neopterin before, during, and after a severe respiratory outbreak and showed that levels corresponded to respiratory symptoms and predicted mortality. While urinary neopterin is sensitive enough to detect changes in immune system activation during severe disease, future research should still aim to validate its use in mild diseases, such as malaria. Finally, human-to-animal disease transmission is known to occur in TNP, with direct declines in chimpanzee populations observed that resulted from several outbreaks caused by human respiratory diseases. Given the zoonotic origin of malaria parasites in humans, I examined the genetic diversity of malaria parasites infecting humans and non-human primates sharing a habitat. Mosquitoes were also captured to identify potential vectors that may bridge transmission between host species. Only P. malariae was found in both humans and chimpanzees—however, the directionality of cross-species transmission would require a larger sample size to correctly assess. Additionally, no anopheline mosquitoes, the only known vector of mammalian malaria parasites, or mosquitoes positive for human- or great ape-specific malaria parasites were captured—suggesting that transmission events may be rare due to the sparsity of vectors in this region. This thesis shows that malaria epidemiology is a temporally and spatially diverse system that requires the use of longitudinal datasets and diverse sampling schemes. This thesis provides a baseline of data on which future malaria parasite research can build. Additionally, the validation of urinary neopterin will allow researchers to pursue questions on how mild diseases affect host health and to investigate questions relating to strategies and variations in life history trade-offs. This thesis is relevant for research on wildlife disease ecology, eco-immunology, and in the creation of pathogen and health surveillance programs.

Large-scale land-use change across the tropics has led to the decline of animal populations and their habitat. With large investments into mining, hydropower dams and industrial agriculture this trend is likely to continue. Consequently, there is a need for systematic land-use planning to set aside areas for protection and allocate scarce conservation funding effectively. Even though primates are relatively well studied, data-driven systematic planning is still rarely implemented. The overall aim of this dissertation was to investigate population parameters needed for evidence-based conservation planning for the critically endangered western chimpanzee (Pan troglodytes verus) in West Africa. To this end, I compiled density datasets covering the entire geographic range of this taxon from the IUCN SSC A.P.E.S. database and modeled chimpanzee densities as a function of 20 social-ecological variables. I found that western chimpanzees seemingly persist within three social-ecological configurations: rainforests with a low degree of anthropogenic threats, steep areas that are less likely to be developed and are harder to access by humans, and areas with a high prevalence of cultural taboos against hunting chimpanzees. The third configuration of reduced hunting pressure is not yet reflected in commonly implemented conservation interventions, suggesting a need for designing new approaches aimed at reducing the threat of hunting. Based on the modeled density distribution, I estimated that 52,811 (95% CI 17,577-96,564) western chimpanzees remain in West Africa, and identified areas of high conservation value to which conservation interventions should be targeted. These results can be used to inform the expansion of the protected area network in West Africa, to quantify the impact of planned industrial projects on western chimpanzees, and to guide the systematic allocation of conservation funding. In addition, this thesis highlights the unique position of taxon-specific databases of providing access to high-resolution data at the scale needed for conservation planning. Data-driven conservation planning has the potential to enable conservationists to respond more proactively to current and emerging threats, and ultimately improve conservation outcomes.