Biology subjects

Soldati, A.

Publications and source records attributed to Soldati, A..

4 recordsLinked to original sources

bioRxiv2025

Testing methodological and population-specific influences on the detection of Zipf's law of brevity in chimpanzee gestures

Zipfs law of brevity is a widespread manifestation of information compression found across human languages and other communication systems. Chimpanzee gesture represents a rare absence of its expression in short-range communication. But, whether this absence reflects a feature of ape gesture production, or results from methodological obstacles or population differences is unclear. Selecting the appropriate unit of analysis is crucial for detecting linguistic patterns in any system. We assess gestural repertoires of three chimpanzee communities for Zipfs law, while discriminating and testing different levels of unit durations (segmentation) and how finely gestural units are split (granularity). We report the first repertoire-wide detection of Zipfs law in ape gesture in one chimpanzee community at a specific level of segmentation and granularity. We suggest that both methodological and socio-ecological factors can shape the detection and expression of Zipfs law, emphasizing the importance of species-relevant units and metrics for meaningful cross-species comparisons.

animal behavior and cognition↗

bioRxiv2024

Sex differences in pant-hoot vocalizations in wild Eastern chimpanzees

Chimpanzee pant-hoots are frequently produced long-distance vocalisations that serve a number of social functions, such as to indicate coordinate travelling, food discovery, or social status. Calling often triggers replies by others, offering potential for some form of group-level decision-making through vocal exchanges. However, despite important physiological and social differences between male and female chimpanzees, pant-hoot research has traditionally focused on males, with very little known about female use. To address this gap, we collected all-occurrence behavioural data from wild adult female and male Eastern chimpanzees (Pan troglodytes schweinfurthii) in two communities in the Budongo Forest Reserve, Uganda. We show that females pant-hooted regularly, but less frequently than males and, when they did so, mostly in response to others. Response pant- hoots were more common than initiating pant-hoots in both sexes (females: 90.1%; males: 69.5%), and male and female chimpanzees responded to pant-hoots heard at a similar rate (females: 14.1%, males excluding alpha: 15.8%). Both sexes were more likely to respond to pant-hoots from within their own party, but this effect was stronger for females. The likelihood of male chimpanzees pant-hooting in response was inhibited in larger party sizes, while females response pant-hoots were not. Finally, female response pant-hoots were less common during periods of maximal oestrous as compared to other stages of their reproductive cycle. Overall, our findings demonstrate that response pant-hoots are subject to social factors, such as within-sex social competition and between-sex reproductive strategies, which affect male and female chimpanzees in different ways, a further demonstration of the high degree of audience awareness in this primate species. HighlightsO_LIChimpanzees use pant-hoots in both sex-specific and sex-non-specific ways C_LIO_LIIndividual and social factors impact likelihood of pant-hoot production C_LIO_LIOur findings suggest pant-hoots are important flexible elements of vocal behaviour for male and female chimpanzees. C_LI

animal behavior and cognition↗

bioRxiv2024

Predictability of next elements in chimpanzee gesture sequences

Recent research has produced evidence for basic combinatorial abilities in the vocal systems of different animal species. Here, we investigate the structure of gesture sequences in Eastern chimpanzees (Pan troglodytes schweinfurthii) to detect whether gestural communication shows non-random combinations and how combinatorial rules influence predictability. Gesture, as compared to vocalization, offers greater flexibility in how signals are combined--for example overlapping in time -- and as the parsing of signals into sequences is dependent on researcher decisions, we employ a multiverse approach, considering four different definitions of what constitutes a sequence based on varying time thresholds. Our results indicate that sequences tend to be short (even with the most liberal time-window) and that transitions between some gesture types occur more frequently than expected by chance, with some transitions showing significant association across all time-windows. These transitions often involve repetition, suggesting persistence as a key aspect of chimpanzee gestural sequences. Information about previous gestures reduced uncertainty in predicting subsequent gestures. The order of gestures within sequences appears to be less critical than their cooccurrence, challenging assumptions based on the linear patterning derived from vocal communication. Our findings highlight the importance of methodological choices in sequence definition and suggest that chimpanzee gestural communication is characterised by a mix of predictability and flexibility, with implications for understanding the evolution of complex communication systems.

animal behavior and cognition↗

bioRxiv2021

Dead infant carrying by chimpanzee mothers in the Budongo Forest

It has been suggested that non-human primates can respond to deceased conspecifics in ways that suggest they experience psychological states not unlike humans, some of which could indicate they exhibit a notion of death. Here, we report long-term demographic data from two East African chimpanzee groups. During a combined 40-year observation period we recorded 191 births of which 68 died in infancy, mostly within the first year. We documented the post-mortem behaviour of the mothers and describe nine occasions where Budongo chimpanzee mothers carried infants for 1-3 days after their death, usually until the body started to decompose. We also observed three additional cases of extended carrying lasting for more than two weeks, one of which was followed by the unusual extended carrying of an object and another which lasted three months. In each case, the corpses mummified. In addition, we report four instances of recurring dead infant carrying by mothers, three of whom carried the corpse for longer during the second instance. We discuss these observations in view of functional hypotheses of dead infant carrying in primates and the potential proximate mechanisms involved in this behaviour.

animal behavior and cognition↗