Biology subjects

Widdig, A.

Publications and source records attributed to Widdig, A..

8 recordsLinked to original sources

bioRxiv2026

The chemistry of families: Linking body odor composition to olfactory perception

Body odors inform human kin recognition. However, underlying chemical mechanisms and how they relate to body odor perception are still unclear. The present study therefore simultaneously examined perceptual body odor similarity according to human raters, its chemical basis and the link between the two in human families. The study included 33 raters who assessed body odors collected from 60 odor donors belonging to 15 biological families. Each family comprised a mother, a father and one adolescent same-sex sibling-dyad (8 sister dyads, 7 brother dyads). Body odor sampling was conducted with cotton pads for presentation to human raters and with thermal desorption (TD) tubes for Gas Chromatography-Mass Spectrometry (GC-MS) analysis. Relatedness and sex predicted perceived body odor similarity in parent-offspring versus unrelated control dyads. Analyses of chemical profiles revealed greater body odor similarity within families than between unrelated individuals. Parallel to the perceptual results, relatedness and sex predicted chemical similarity based on whole odor profiles. Finally, a machine-learning prediction model integrating perceptual and chemical data, revealed a small but significant positive association between chemical similarity of body odor and perceived olfactory similarity according to human raters, suggesting that odor perception is partly informed by chemical characteristics. Overall, the present study extends our understanding of human chemosensory communication and supports the notion of a family-specific olfactory signature.

ecology↗

bioRxiv2026

Comparing genomic inbreeding of an isolated rhesus macaque study population to wild populations

Long-term studies of isolated animal populations have greatly improved the understanding of various evolutionary processes. However, potentially elevated inbreeding in those compared to wild populations is a common concern. Conventionally, inbreeding has been investigated using reconstructed pedigrees, but nowadays it can be done directly at the genomic level. Here, we utilise genomic data from an intensively studied isolated rhesus macaque (Macaca mulatta) population on the small island Cayo Santiago (Puerto Rico), founded in 1938 with wild animals from India. We quantified inbreeding levels by inferring runs of homozygosity (ROH), i.e., long identical haplotypes inherited from both parents. We identified ROH in 97 [~]5x-coverage genomes from Cayo Santiago and, for comparison, in 79 rhesus macaque genomes from five wild populations from China. Notably, this conventionally considered low-coverage data proved sufficient to infer ROH > 4 centimorgans long after imputing the genomes using a reference panel. Our results revealed that the ROH-derived effective population size on Cayo Santiago, 420 individuals, falls within the ranges we inferred in wild populations. Moreover, a general scarcity of individuals with long ROH in both the Cayo and wild populations indicates very few cases of close-kin breeding, suggesting that mechanisms to avoid close-kin breeding operate in rhesus macaques, in both wild and isolated populations. Taken together, our results suggest that Cayo Santiago remains a representative study population.

evolutionary biology↗

bioRxiv2026

Multimodal fertility cues in chimpanzees: How body odours complement sexual swellings

To attract mating partners, female mammals communicate their reproductive status through one or multiple sensory modalities, providing redundant or complementary information. Chimpanzees (Pan troglodytes) are an excellent model for studying multimodal communication. Exaggerated sexual swellings of females serve as a visual proxy for ovulation but increased male mating interest during maximum swelling suggests that olfactory cues may pinpoint fertility more accurately than the swelling alone. Here, we combined gas chromatography-mass spectrometry, hormonal analyses, and bioassays to examine (1) whether chemical composition of female anogenital odours changes during the fertile period, and (2) whether males are able to detect these changes. Our results suggest that, in addition to prominent olfactory changes associated with swelling stages, chemical cues provide complementary information regarding the timing of the fertile window. These changes, however, are minor compared to those related to swelling stages. Male behavioural responsiveness in bioassays was too low to draw conclusions regarding their ability to detect these subtle shifts when presented with a chemical cue only. Overall, our findings support the existence of a multimodal fertility cue in chimpanzees, wherein visual signals are complemented by subtle olfactory changes indicating the timing of the fertile period.

animal behavior and cognition↗

bioRxiv2025

Early life adversity shapes life history trade-offs between growth and reproduction in free-ranging rhesus macaques

Life history theory predicts that organisms allocate resources across physiological processes to maximize fitness. Under this framework, early life adversity (ELA)--which often limits energetic capital--could shape investment in growth and reproduction, as well as trade-offs between them, ultimately contributing to variation in evolutionary fitness. Using long-term demographic, behavioral, and physiological data for 2,100 females from a non-human primate population, we tested whether naturally-occurring ELA influences investment in the competing physiological demands of growth and reproduction. By analyzing ELA, growth, and reproduction in the same individuals, we also assessed whether adversity intensifies trade-offs between life history domains. We found that ELA influenced life history patterns, and was associated with modified growth, delayed reproductive maturity, and small adult body size. Different types of ELA sometimes had distinct reproductive outcomes--e.g., large group size was linked to faster reproductive rates, while low maternal rank predicted slower ones. Adversity also amplified trade-offs between growth and reproduction: small body size was a stronger predictor of delayed and reduced reproductive output in females exposed to ELA, compared to those not exposed. Finally, we examined how traits modified by ELA related to lifetime reproductive success. Across the population, starting reproduction earlier and maintaining a moderate reproductive rate conferred the greatest number of offspring surviving to reproductive maturity. These findings suggest that ELA impacts key life history traits as well as relationships between them, and can constrain individuals from adopting the most optimal reproductive strategy. Significance StatementEarly life adversity (ELA) can have lasting effects on evolutionary fitness (e.g., the number of surviving offspring an animal produces); however, the paths connecting ELA to fitness--for example by influencing growth, reproductive timing or rate, or trade-offs between these processes--remain unclear. Leveraging long-term behavioral, physiological, and demographic data from 2,100 female rhesus macaques, we found that ELA-exposed females exhibited growth and reproductive schedules associated with less-optimal lifetime fitness outcomes. Further, ELA intensified trade-offs between growth and reproduction, suggesting that affected individuals face steeper energetic constraints. Our findings highlight the long-lasting impacts of ELA on traits of evolutionary and biomedical importance in a non-human primate model with relevance to humans.

evolutionary biology↗

bioRxiv2024

Chemical signatures of social information in Barbary macaques

Primates are well-known for their complex social lives and intricate social relationships, which requires them to obtain and update social knowledge about conspecifics. The sense of smell may provide access to social information that is unavailable in other sensory domains or enhance the precision and reliability of other sensory cues. However, the cognition of social information in catarrhine primates has been studied primarily in the visual and auditory domain. We assessed the social information content of body odor in a catarrhine primate, the Barbary macaque (Macaca sylvanus), in three semi-free ranging groups at Affenberg Salem, Germany. In particular, we related socially relevant attributes (identity, genetic relatedness, rank, sex, age, group membership) to chemical profiles of body odor. We applied non-invasive active sampling via thermal desorption tubes and analyzed samples by gas chromatography-mass spectrometry. We found robust evidence for individual odor signatures and limited support for kin signatures. Chemical profiles were also related to group membership, but little to rank, sex or age. The detected associations between chemical profiles and socially relevant attributes form the theoretical foundations for olfactory information transfer, highlighting the potential of body odor to provide valuable social information in this highly visually oriented primate.

animal behavior and cognition↗

bioRxiv2024

Taking identity-by-descent analysis into the wild: Estimating realized relatedness in free-ranging macaques

Biological relatedness is a key consideration in studies of behavior, population structure, and trait evolution. Except for parent-offspring dyads, pedigrees capture relatedness imperfectly. The number and length of DNA segments that are identical-by-descent (IBD) yield the most precise estimates of relatedness. Here, we leverage novel methods for estimating locus-specific IBD from low coverage whole genome resequencing data to demonstrate the feasibility and value of resolving fine-scaled gradients of relatedness in free-living animals. Using primarily 4-6x coverage data from a rhesus macaque (Macaca mulatta) population with available long-term pedigree data, we show that we can call the number and length of IBD segments across the genome with high accuracy even at 0.5x coverage. The resulting estimates demonstrate substantial variation in genetic relatedness within kin classes, leading to overlapping distributions between kin classes. They identify cryptic genetic relatives that are not represented in the pedigree and reveal elevated recombination rates in females relative to males, which allows us to discriminate maternal and paternal kin using genotype data alone. Our findings represent a breakthrough in the ability to understand the predictors and consequences of genetic relatedness in natural populations, contributing to our understanding of a fundamental component of population structure in the wild.

ecology↗

bioRxiv2023

Influence of visual information on sniffing behavior in a routinely trichromatic primate

Most catarrhine primates are considered to be strongly visually oriented, obtaining information about conspecifics and their environment from a diversity of visual cues. Other sensory modalities may provide information that is redundant and/or complimentary to visual cues. When cues from multiple sensory modalities are available, these may reinforce or suppress each other, as shown in several taxa ranging from insects to humans. Here, we tested how the presence and ambiguity of visual information affects the use of olfactory cues when exploring food and non-food items in semi-free ranging Barbary macaques at Affenberg Salem, Germany. We presented monkeys with pipes containing food (peanuts, popcorn), non-food (stones, feces) or no items in transparent or opaque containers, and assessed whether animals looked, sniffed and/or grabbed into the pipes depending on visibility of the contents (experiment 1). Visual information had no robust effect on sniffing probability, but it did affect sniffing behavior with respect to the timing of olfactory inspections (i.e. whether sniffing occurred first). Both visual and olfactory information affected, whether or not monkeys attempted to retrieve the items from the pipes. Furthermore, we manipulated the visual appearance of familiar food items (popcorn) with food colorant (experiment 2), which resulted in substantially increased olfactory inspections compared to unmanipulated popcorn. Taken together, reliance on the olfactory sense was modulated by the available visual information, emphasizing the interplay between different sensory modalities for obtaining information about the environment.

animal behavior and cognition↗

bioRxiv2022

Sniffing behaviour of Barbary macaques at Affenberg Salem

Olfaction is one of the evolutionarily oldest senses and plays a fundamental role in foraging and social interactions across mammals. In primates, the role of olfaction is now well recognized, but better investigated in strepsirrhine and platyrrhine primates than in catarrhines. We observed the sniffing behavior of semi-free ranging Barbary macaques, Macaca sylvanus, at Affenberg Salem, Germany, to assess how frequently macaques sniff and in which contexts, and how sniffing is affected by sex and age. Focal observations of 24 males and 24 females aged 1 to 25 years showed that Barbary macaques sniffed, on average, 5.3 times per hour, with more than 80% of sniffs directed at food. Irrespective of the context, younger individuals sniffed more often than older ones. Females sniffs were more often directed at food than male sniffs, while males sniffed more often than females in a social context. Sniffs at conspecifics occurred primarily in a sexual context, with 70% of social sniffs directed at female anogenital swellings performed by males. Of the observed 176 anogenital inspections, 51 involved sniffing of the swelling. Olfactory inspections were followed by copulation significantly less often than merely visual inspections, suggesting that anogenital odors provided additional information guiding male mating decisions. In sum, results show that Barbary macaques routinely use olfaction during feeding, but also in a social context. Our study further suggests that odors may guide mating decisions, but the role of olfaction in sexual interactions warrants further investigations.

animal behavior and cognition↗