An important element in understanding the evolutionary origin of human language is to explore homologous traits in cognition and communication between primates and humans (Burling, 1993, Hewes, 1973). One proposed modality of language evolution is that of gestural communication, defined as communicative movements of hands without using or touching objects (de Waal, 2003). While homologies between primate calls and language have been relatively well explored, we still have a limited understanding of how cognitive abilities may have shaped the characteristics of primate gestures (Corballis, 2003). Chimpanzees (Pan troglodytes) are our closest living relatives and display some complex cognitive skills in various aspects of their gestural behaviour in captivity (de Waal, 2003, Pollick and de Waal, 2007). However, it is not yet currently clear to what extent these abilities seen in captive apes are typical of chimpanzees in general and to what extent cognitive capacities observed in captive chimpanzees have been enhanced by the socio-cultural environment of captivity such as language training. In this Ph.D. research, I investigated the cognitive skills underlying gestural communication in both wild and language trained chimpanzees, with a special focus on the repertoire and the intentionality of production and comprehension. The study of cognitive skills underlying the production of the repertoire and the role of intentionality is important because these skills are cognitively demanding and are a prerequisite in human infants for their ability to acquire language (Baldwin, 1995, Olson, 1993). My research suggests that chimpanzee gestural communication is cognitively complex and may be homologous with the cognitive skills evident in pre-verbal infants on the cusp of language acquisition. Chimpanzees display a multifaceted and complex signal repertoire of manual gestures. These gestures are the prototypes, within which there is variation, and between which the boundaries are not clear-cut, but there is gradation apparent along several morphological components. Both wild and language trained chimpanzees communicate intentionally about their perceived desires and the actions that they want the recipients to undertake. They do not just express their emotions, but they communicate flexibly by adjusting their communicative tactics in response to the comprehension states of the recipient. Whilst chimpanzees communicate their intentions flexibly, the messages conveyed are specific. However, recipients comprehend gestures flexibly in light of the signaller’s overall intentions. Whilst wild and language trained chimpanzee gestural communication revealed similar cognitive characteristics, language trained chimpanzees outperformed wild apes in that they had ability to use signals which made distinctions that human deictic words can make. Whilst these differences between wild and language trained chimpanzees may be due to the different methodological approaches used, it is conceivable that language training may have influenced captive ape cognitive skills in the representational domain. These results from wild and language trained chimpanzees indicate that chimpanzees possess some form of cognitive skills necessary for language development and that cognitive skills underlying repertoire and use in chimpanzees are a shared capacity between humans, other apes and a common ancestor. These findings render theories of the gestural origins of language more plausible. Related publications: 1. Roberts, A. I., Vick, S.-J., Roberts, S. G. B., Buchanan-Smith, H. M. & Zuberbühler, K. 2012. A structure-based repertoire of manual gestures in wild chimpanzees: Statistical analyses of a graded communication system. Evolution and Human Behavior, Published online: http://dx.doi.org/ 10.1016/j.evolhumbehav.2012.05.006 2. Roberts, A. I., Vick, S.-J. & Buchanan-Smith, H. 2012. Usage and comprehension of manual gestures in wild chimpanzees. Animal Behaviour, Published online: http://dx.doi.org/10.1016/j.anbehav.2012.05.022

One important part of the management of zoo populations is the exchange of animals. The removal of an individual can have unknown effects on the social dynamics of the group. Social network studies are a well-established method to describe the social interactions within a group. This study aims to describe the social interactions in a group of chimpanzees and to test how social dominance rank predicts social interaction patters using a social network approach. Data was collected via observations on Kolmarden Wildlife Parks chimpanzee group, which is composed of seven males and eleven females. A total of 50 h of data was collected over 16 days. This resulted in a dominance rank and four different social networks for different behaviors (touch proximity, proximity, affiliative and agonistic behavior). The eigenvector coefficient, with the notable exception of the proximity network, was rarely correlated with the dominance rank and the highest ranked individual was never the most central. The more dominate individuals had fewer links to others through proximity and affiliative interactions. My analysis of the social network structure provides some evidence that the removal of high-ranking individuals would be unlikely to disproportionally affect the structure of the social network in this group. I highlight the possibility of further analysis such as knock-out analysis (where you examine the consequences of the removal of specific individuals) on existing data and argue that more observations would help to draw up a well-structured plan for translocations of individuals in this group. / En viktig del i förvaltningen av djurparkspopulationer är utbytet av djur. Att flytta en individ från en grupp kan ha okända effekter på gruppens sociala dynamik. Studier av djurs sociala nätverk är en väletablerad metod för att beskriva sociala interaktioner inom en grupp av djur. Syftet med denna studie är att beskriva de sociala interaktionerna i en grupp av schimpanser och testa huruvida en ranking av dominans förutspår mönster i dessa sociala interaktioner genom att tillämpa ’social network analysis’ metoden. Observationsdata samlades in på Kolmårdens djurparks schimpansgrupp, som består av sju hanar och elva honor. Totalt samlades 50 timmar av data under 16 dagar. Detta resulterade i en dominansrankning och fyra olika nätverk för olika typer av sociala interaktioner (närhet med beröring, närhet, affiliativa och agnostiska beteenden). Egienvector koefficienten, med det anmärkningsvärda undantaget för närhets nätverket, var sällan korrelerat med dominansrankningen och den högst rankade individen var aldrig mest central. Mer dominanta individer hade färre länkar till andra genom närhet med beröring och affiliativa interaktioner. Mina analyser av de sociala nätverkens struktur ger vissa bevis för att borttagandet av högt rankade individer inte skulle ge oproportionerliga effekter på den sociala strukturen i denna grupp. Jag uppmärksammar också möjligheterna att med mer analyser som t.ex. knock-out analyser (där man undersöker konsekvensen av att ta bort individer från olika nätverk) på befintlig data, samt mer observationer skulle hjälpa för att kunna göra en väl strukturerad plan för flytt av individer från denna grupp.

Chimpanzees are highly social animals, presenting a wide variety of social interactions among them. In this study, we compared the social dynamics in a group of 20 captive chimpanzees at Kolmården Wildlife Park between two different exhibits: outdoors (summer) and indoors (autumn). Furthermore, different types of enrichment were offered in both environments and we investigated how the presence and the type of enrichment (food-based) affected the social interactions in the group. Then, we used the frequencies of the social interactions to analyse the social dynamics in the group. Our results showed that the chimpanzees had significantly higher frequencies of proximity, allogrooming and displacement in the outdoor exhibit compared to indoor one and higher frequencies of threat and display indoors compared to outdoors. Moreover, we found that associative and affiliative behaviours increased in both outdoor and indoor exhibits when enrichment was absent compared to when it was present and also when enrichment was absent compared to when food-based enrichment was offered. Furthermore, three pairs of individuals, all mother-daughter dyads, were found to have preferred relationships. In the allogrooming network, one female, the only one that was in estrus, was found to be the most common recipient of allogrooming. Finally, the oldest male, father of all offspring, was, as expected, ranked as the most dominant in the group, based on the agonistic interactions. Our results may be used by the zoo staff to further develop their management practices to improve chimpanzees’ welfare.