Chimpanzees combine pant hoots with food calls into larger structures

This work was supported by the Swiss National Science Foundation (PP00P3_163850) to S.W.T. and the NCCR Evolving Language (Swiss National Science Foundation Agreement #51NF40_180888).A growing body of observational and experimental data in nonhuman primates has highlighted the presence of rudimentary call combinations within the vocal communication system of monkeys. Such evidence suggests the ability to combine meaning-bearing units into larger structures, a key feature of language also known as syntax, could have its origins rooted within the primate lineage. However, the evolutionary progression of this trait remains ambiguous as evidence for similar combinations in great apes, our closest-living relatives, is sparse and incomplete. In this study, we aimed to bridge this gap by analysing the combinatorial properties of the pant hoot–food call combination in our closest-living relative, the chimpanzee, Pan troglodytes. To systematically investigate the syntactic-like potential of this structure, we adopted three levels of analysis. First, we applied collocation analyses, methods traditionally used in language sciences, to confirm the combination of pant hoots with food calls was not a random co-occurrence, but instead a consistently produced structure. Second, using acoustic analyses, we confirmed pant hoots and food calls comprising the combination were acoustically indistinguishable from the same calls produced in isolation, indicating the pant hoot–food call combination is composed of individually occurring meaning-bearing units, a key criterion of linguistic syntax. Finally, we investigated the context-specific nature of this structure, demonstrating that the call combination was more likely to be produced when feeding on larger patches and when a high-ranking individual joined the feeding party. Together our results converge to provide support for the systematic combination of calls in chimpanzees. We highlight that playback experiments are vital to robustly disentangle both the function this combination might serve and the similarities with combinations of meaning-bearing units (i.e. syntax) in language.Publisher PDFPeer reviewe

Controlling invasive rodents via synthetic gene drive and the role of polyandry

House mice are a major ecosystem pest, particularly threatening island ecosystems as a non-native invasive species. Rapid advances in synthetic biology offer new avenues to control pest species for biodiversity conservation. Recently, a synthetic sperm-killing gene drive construct called t-Sry has been proposed as a means to eradicate target mouse populations owing to a lack of females. A factor that has received little attention in the discussion surrounding such drive applications is polyandry. Previous research has demonstrated that sperm-killing drivers are extremely damaging to a male’s sperm competitive ability. Here, we examine the importance of this effect on the t-Sry system using a theoretical model. We find that polyandry substantially hampers the spread of t-Sry such that release efforts have to be increased three- to sixfold for successful eradication. We discuss the implications of our finding for potential pest control programmes, the risk of drive spread beyond the target population, and the emergence of drive resistance. Our work highlights that a solid understanding of the forces that determine drive dynamics in a natural setting is key for successful drive application, and that exploring the natural diversity of gene drives may inform effective gene drive design

Female nursing partner choice in a population of wild house mice (Mus musculus domesticus)

Background Communal nursing in house mice is an example of cooperation where females pool litters in the same nest and indiscriminately nurse own and other offspring despite potential exploitation. The direct fitness benefits associated with communal nursing shown in laboratory studies suggest it to be a selected component of female house mice reproductive behaviour. However, past studies on communal nursing in free-living populations have debated whether it is a consequence of sharing the same nest or an active choice. Here using data from a long-term study of free-living, wild house mice we investigated individual nursing decisions and determined what factors influenced a female’s decision to nurse communally. Results Females chose to nurse solitarily more often than expected by chance, but the likelihood of nursing solitarily decreased when females had more partners available. While finding no influence of pairwise relatedness on partner choice, we observed that females shared their social environment with genetically similar individuals, suggesting a female’s home area consisted of related females, possibly facilitating the evolution of cooperation. Within such a home area females were more likely to nest communally when the general relatedness of her available options was relatively high. Females formed communal nests with females that were familiar through previous associations and had young pups of usually less than 5 days old. Conclusions Our findings suggest that communal nursing was not a by-product of sharing the same nesting sites, but females choose communal nursing partners from a group of genetically similar females, and ultimately the decision may then depend on the pool of options available. Social partner choice proved to be an integrated part of cooperation among females, and might allow females to reduce the conflict over number of offspring in a communal nest and milk investment towards own and other offspring. We suggest that social partner choice may be a general mechanism to stabilize costly cooperation

Resistance to natural and synthetic gene drive systems

Scientists are rapidly developing synthetic gene drive elements intended for release into natural populations. These are intended to control or eradicate disease vectors and pests, or to spread useful traits through wild populations for disease control or conservation purposes. However, a crucial problem for gene drives is the evolution of resistance against them, preventing their spread. Understanding the mechanisms by which populations might evolve resistance is essential for engineering effective gene drive systems. This review summarizes our current knowledge of drive resistance in both natural and synthetic gene drives. We explore how insights from naturally occurring and synthetic drive systems can be integrated to improve the design of gene drives, better predict the outcome of releases and understand genomic conflict in general

Resistance to natural and synthetic gene drive systems

Scientists are rapidly developing synthetic gene drive elements intended for release into natural populations. These are intended to control or eradicate disease vectors and pests, or to spread useful traits through wild populations for disease control or conservation purposes. However, a crucial problem for gene drives is the evolution of resistance against them, preventing their spread. Understanding the mechanisms by which populations might evolve resistance is essential for engineering effective gene drive systems. This review summarizes our current knowledge of drive resistance in both natural and synthetic gene drives. We explore how insights from naturally occurring and synthetic drive systems can be integrated to improve the design of gene drives, better predict the outcome of releases and understand genomic conflict in general

Polyandry blocks gene drive in a wild house mouse population

Gene drives are genetic elements that manipulate Mendelian inheritance ratios in their favour. Understanding the forces that explain drive frequency in natural populations is a long-standing focus of evolutionary research. Recently, the possibility to create artificial drive constructs to modify pest populations has exacerbated our need to understand how drive spreads in natural populations. Here, we study the impact of polyandry on a well-known gene drive, called t haplotype, in an intensively monitored population of wild house mice. First, we show that house mice are highly polyandrous: 47% of 682 litters were sired by more than one male. Second, we find that drive-carrying males are particularly compromised in sperm competition, resulting in reduced reproductive success. As a result, drive frequency decreased during the 4.5 year observation period. Overall, we provide the first direct evidence that the spread of a gene drive is hampered by reproductive behaviour in a natural population

Internal acoustic structuring in pied babbler recruitment cries specifies the form of recruitment

Language is inherently combinatorial, and parallels of this combinatorial capacity are found in nonhuman systems, with animals combining sounds and calls into larger meaningful structures. However, further analogue examples are central in unveiling the diversity, distribution, and evolutionary drivers of combinatoriality. Here, we provide evidence for internal “meaning-refining” acoustic variation within a larger stereotyped signal in pied babblers (Turdoides bicolor). Using acoustic analyses, we demonstrate that males produce 2 long, raucous, “cry-like” structures, both starting with a wind-up segment grading into repetitions of A/single-note or AB/double-note motifs. Behavioral observations indicated that, consistent with similarities in their larger stereotyped structure, both variants function overall in recruiting group members during locomotion, but the internal A or AB substructure specifies the “precise” form of recruitment, from approaching the caller’s announced location to following it over longer distances. Playing back cries from a stationary loudspeaker further supported that the 2 variants elicit different responses, with more individuals approaching the loudspeaker in response to single-note compared with double-note cries. Additionally, despite similarities in overall distance travelled, group movement was only directional for single-note, but undefined for double-note cries. We suggest that the overall structure of the 2 cry variants conveys the same general meaning, with embedded variation refining this meaning. These results further illustrate the variability of generative mechanisms outside of human language and lend support to the hypothesis that combinatorial structuring may have emerged in species with limited or fixed vocal repertoires in order to enhance communicative output

Data from: Female house mice avoid fertilization by t haplotype incompatible males in a mate choice experiment

The t haplotype in house mice is a well-known selfish genetic element with detrimental, nonadditive fitness consequences to its carriers: recessive lethal mutations cause t/t homozygotes to perish in utero. Given the severe genetic incompatibility imposed by the t haplotype, we predict females to avoid fertilization by t haplotype incompatible males. Indeed, some of the strongest evidence for compatibility mate choice is related to the t haplotype in house mice. However, all previous evidence for compatibility mate choice in this system is based on olfactory preference. It is so far unknown how general these preferences are and whether they are relevant in an actual mating context. Here, we assess female compatibility mate choice related to t haplotypes in a setting that – for the first time – allowed females to directly interact and mate with males. This approach enabled us to analyse female behaviour during the testing period, and the resulting paternity success and fitness consequences of a given choice. We show that genetic incompatibilities arising from the t haplotype had severe indirect fitness consequences and t females avoided fertilization by t incompatible males. The results are inconclusive whether this avoidance of t fertilization by t females was caused by pre- or post-copulatory processes