This project aims to understand how individuals move in coordination with each other in a fission fusion society as seen from the chimpanzees of the Issa Valley, Tanzania. This would entail understanding how multiple individuals can move in relation to one another from a distance. In fission fusion societies individuals form subgroups whose compositions are spatiotemporally dependent. The study of this coordination requires investigating the factors affecting communication and the consequent decision making the individuals make on movement and possible leadership. To overcome the logistical challenge of monitoring communication between individuals across long distances, machine learning algorithms will be used to analyse media from remote sensing technology recording simultaneously from multiple locations to identify callers and responders. whilst inter-party communication has been established as a mode for coordination, call producer and responder behaviour, requires further investigation. Specifically how social relationships affect which individuals communicate with who. Relatedly, I will address questions that integrate vocal behaviour with leadership, and what role these two key elements play in social (spatial) coordination. This project will uncover information on how fission fusion societies coordinate movement, long-distance communication between individuals, the movement of an endangered primate: the common chimpanzee. Furthermore, the chimpanzees of the Issa valley inhabit an environment that closely resembles the paleoenvironment of several early hominin species. Therefore they may provide a landscape analogous to how these hominins may have coordinated in these woodland savannah mosaic habitats. Understanding the mechanisms by which individuals and sub-groups coordinate between each other - in both auditory and visual domains - can provide us insights into how individuals optimise the benefits of group living while minimising the costs. We can then see how this coordination impacts their movement as a community.

Who communicates with who Communication, and especially coordination, is a key element for reunions between members of fission-fusion societies, where individuals are spatially and temporally separated for variable time periods. While there is historic interest in the function of chimpanzee loud calls (Fedurek et al., 2016, 2021; Mitani & Nishida, 1993), and how social factors specifically affect the likelihood of producing these vocalisations used for coordination (Mitani and Nishida, 1993), there has been little investigation into the response behaviour of these loud calls. Response behaviour of communication for group coordination has been limited to close-distance soft “hoo” type vocalisations (Bouchard & Zuberbühler, 2022; Crockford et al., 2017) but this study will be the first to examine the response behaviour of loud calling vocalisations, providing insight into the spatial coordination of these fission and fusion dynamics at a much larger scale. Communication via loud calls such as pant-hoots, and buttress drumming, produced during travelling, is individually encoded and thus likely to be critical to decisions individuals make to join or avoid conspecifics (Desai et al., 2022; Eleuteri et al., 2022; Fedurek et al., 2021). However, due to the logistical challenge of simultaneously observing multiple parties across a large area, studies addressing caller-responder dynamics in large groups of large-bodied animals are limited. By identifying these responders (and non-responders) we can examine how vocalisations are used to recruit allies and selectively share information on caller identity and activity to other parties. Information can be selectively shared by masking parts of their vocalisations with noise using branches or shortening the duration of their call (Grampp et al., 2023). Using artificial intelligence and remote monitoring, this study will be the first to assess how relationship quality impacts communication and movement across a mosaic landscape. Similar to the chimpanzees of the Issa Valley, early hominins are hypothesised to have had fission fusion social dynamics (Grove et al., 2012) in male-based philopatric societies (Copeland et al., 2011; Milich, 2024), which would have required coordination (Negash et al., 2024). Therefore, by understanding how the Issa chimpanzees coordinate their movement we may gain insight into how other male philopatric fission-fusion societies (e.g. australopithecines (Copeland et al., 2011)) may have navigated comparable open landscapes. I predict that the social correlates of response behaviour will reflect those of the initial callers as described by Mitani and Nishida (1993), where responders to callers are most likely to be individuals most closely associated to the caller and communication is most likely to occur between high ranking and/or older males. This aligns well with the mission of the Leakey foundation to better understand human origins through investigating aspects of hominin social behaviour using extant models. Leadership as a driver of fission fusion dynamics The results of this study will have impacts beyond primatology and our understanding of fission fusion dynamics. To understand these dynamics, the decision making process between group members and the consequent leadership that arises during travelling need to be investigated. Whilst resource distribution and sexual reproductive opportunities drive individual decision making in chimpanzees (Matthews et al., 2021), we know very little how leadership drives fission and fusion dynamics in this species. In other fission-fusion systems different factors have been shown to affect how individuals choose to follow who during fission events such as age (McComb et al., 2011), who has the most meaningful knowledge of the area (Lewis et al., 2011; Merkle et al., 2015), and social connectedness (Merkle et al., 2015; Sueur et al., 2010). However, we do not know how leadership in fission fusion systems affect fusion events. To investigate this we need to identify the individuals communicating to each other preceding reunion events between parties (Sueur et al., 2011). I predict that in Issa’s chimpanzees, social connectedness as well as age and kin will be primary drivers of which individual communicates and with whom, and how those decisions influence movement and ultimately, community cohesion. In this way, my work will make key contributions to the field of leadership and coordinated movement in fission-fusion systems. Monitoring chimpanzee movements Finally, besides an intellectual contribution to key questions about movement coordination, my work will also advance the field of primate communication by incorporating traditional (focal follow behavioural observations) with innovative technological (motion-triggered cameras and acoustic sensors) methods and neural network algorithms to investigate fission fusion dynamics. Excitingly, this project will also be the first study to employ artificial intelligence and individual level speech recognition from landscape recordings to situate spatiotemporal patterns of individuals. Whilst past audio classification of non-human animals has been limited to convolutional neural networks (Gupta et al., 2021), we will be using recurrent neural networks as used in human speech recognition algorithms (Deng & Li, 2013; but see Leroux et al., 2021). This project will showcase how to use transfer learning to circumnavigate the lack of large datasets typically needed to train neural networks. We propose using algorithms pre-trained on human and/or bird and marine mammal data to then be further trained and fine-tuned to identify individual primates smaller datasets (Ghani et al., 2023; Yu et al., 2020). Given that 65% of primates are threatened with extinction and 75% have declining populations (Estrada et al., 2020; IUCN Red List, 2019), they both are in the most need of monitoring whilst simultaneously lacking data needed to monitor them.

The objectives of this study are to understand how acoustic communication can be used to coordinate movement. Investigating what factors affect the likelihood of an individual responding to an individual, which individuals are most likely to lead a sub-group and why; and finally how leadership and callers are correlated