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The Japanese marten ( Martes melampus ) is a solitary mustelid species with a strict territorial space that might be maintained by scent marking. However, whether Japanese martens have scent glands that secrete chemical signals remains unknown. We aimed to clarify whether the abdominal glands in these animals secrete chemical signals and, if so, to characterize their morphological and histological features. We investigated nine Japanese martens (eight M. m. tsuensis and one M. m. melampus ) that were all roadkilled. Regardless of sex, season, and subspecies, they all had abdominal glands located at the rostral aspect of the penis or vagina, and brown secretions were evident on the skin area. Enlarged sebaceous and small apocrine glands were spread mostly throughout the abdominal glands. Obviously enlarged, specialized glands were located in the caudal and medial areas of the abdominal glands. The specialized and sebaceous gland cells were connected through a duct at the border between them. This suggested that the specialized gland cells were derived from the sebaceous type. However, eosin staining of the specialized gland cells possessing a nucleus was strongly positive for cytoplasm, whereas that of the sebaceous gland cells was weakly positive. Moreover, the specialized gland cells were weakly stained with Oil Red O, whereas the sebaceous gland cells were strongly stained. Thus, the secretory mechanism of the abdominal specialized glands may not be holocrine like sebaceous glands. In conclusion, Japanese martens had characteristic abdominal glands with developed sebaceous and specialized glands.

Scent marks play a crucial role in both territorial and sexual communication in many species. We investigated how free-ranging dogs respond to scent marks from individuals of different identities in terms of sex and group, across varying strategic locations within their territory. Both male and female dogs showed heightened interest in scent marks compared to control, exhibiting stronger territorial responses, with males being more territorial than females. Overmarking behavior was predominantly observed in males, particularly in response to male scent marks and those from neighboring groups. Behavioral cluster analysis revealed distinct responses to different scent marks, with neighboring group male scents eliciting the most distinct reactions. Our findings highlight the multifaceted role of scent marks in free-ranging dog communication, mediating both territorial defense and intrasexual competition. The differential responses based on the identity and gender of the scent-marker emphasize the complexity of olfactory signaling in this species. This study contributes to understanding the social behavior of dogs in their natural habitat, and opens up possibilities for future explorations in the role of olfactory cues in the social dynamics of the species.

All animals harbor beneficial microbes. One way these microbes can benefit their animal hosts is by increasing the diversity and efficacy of communication signals available to the hosts. The fermentation hypothesis for mammalian chemical communication posits that bacteria in the scent glands of mammals generate odorous metabolites used by their hosts for communication and that variation in host chemical signals is a product of underlying variation in the bacterial communities inhabiting the scent glands. An effective test of this hypothesis would require accurate surveys of the bacterial communities in mammals’ scent glands and complementary data on the odorant profiles of scent secretions—both of which have been historically lacking. Here we use next-generation sequencing to survey deeply the bacterial communities in the scent glands of wild spotted and striped hyenas. We show that these communities are dominated by fermentative bacteria and that the structures of these communities covary with the volatile fatty acid profiles of scent secretions in both hyena species. The bacterial and volatile fatty acid profiles of secretions differ between spotted and striped hyenas, and both profiles vary with sex and reproductive state among spotted hyenas within a single social group. Our results strongly support the fermentation hypothesis for chemical communication, suggesting that symbiotic bacteria underlie species-specific odors in both spotted and striped hyenas and further underlie sex and reproductive state-specific odors among spotted hyenas. We anticipate that the fermentation hypothesis for chemical communication will prove broadly applicable among scent-marking mammals as others use the technical and analytical approaches used here.

Estimating abundance of wild animal populations is crucial for their management and conservation. While spatial capture-recapture models are becoming increasingly common to assess the densities of elusive species, recent studies have indicated potential bias that can be introduced by unaccounted spatial variation of detectability. We used camera-trapping data collected in collaboration with local hunters from a transnational population survey of the Eurasian lynx (Lynx lynx) in Slovenia and Croatia, to provide the first density estimate for the threatened Eurasian lynx population in the Northern Dinaric Mountains. Population density was 0.83 (95% CI: 0.60–1.16) lynx/100 km2, which is comparable to other reintroduced Eurasian lynx populations in Europe. Furthermore, we showed that baseline detection rate was influenced by the type of site used, as well as by sex of the individual and local behavioural response. Scent-marking sites had on average a 1.6- and 2.5-times higher baseline detection rate compared to roads and other locations, respectively. Scent-marking behaviour is common for several mammals, and selecting sites that attracts the targeted species is used to increase detection rates, especially for rare and cryptic species. But we show that the use of different location types for camera trapping can bias density estimates if not homogenously distributed across the surveyed area. This highlights the importance of incorporating not only individual characteristics (e.g., sex), but also information on the type of site used in camera trapping surveys into estimates of population densities.

Autism is a neurodevelopmental disorder with a strong genetic component. Core symptoms are abnormal reciprocal social interactions, qualitative impairments in communication, and repetitive and stereotyped patterns of behavior with restricted interests. Candidate genes for autism include the SHANK gene family, as mutations in SHANK2 and SHANK3 have been detected in several autistic individuals. SHANK genes code for a family of scaffolding proteins located in the postsynaptic density of excitatory synapses. To test the hypothesis that a mutation in SHANK1 contributes to the symptoms of autism, we evaluated Shank1(-/-) null mutant mice for behavioral phenotypes with relevance to autism, focusing on social communication. Ultrasonic vocalizations and the deposition of scent marks appear to be two major modes of mouse communication. Our findings revealed evidence for low levels of ultrasonic vocalizations and scent marks in Shank1(-/-) mice as compared to wildtype Shank1(+/+) littermate controls. Shank1(-/-) pups emitted fewer vocalizations than Shank1(+/+) pups when isolated from mother and littermates. In adulthood, genotype affected scent marking behavior in the presence of female urinary pheromones. Adult Shank1(-/-) males deposited fewer scent marks in proximity to female urine than Shank1(+/+) males. Call emission in response to female urinary pheromones also differed between genotypes. Shank1(+/+) mice changed their calling pattern dependent on previous female interactions, while Shank1(-/-) mice were unaffected, indicating a failure of Shank1(-/-) males to learn from a social experience. The reduced levels of ultrasonic vocalizations and scent marking behavior in Shank1(-/-) mice are consistent with a phenotype relevant to social communication deficits in autism.

Organisms have evolved diverse behavioural strategies that enhance the likelihood of encountering and assessing mates 1 . Many species use pheromones to communicate information about the location, sexual and social status of potential partners 2 . In mice, the major urinary protein darcin—which is present in the urine of males—provides a component of a scent mark that elicits approach by females and drives learning 3 , 4 . Here we show that darcin elicits a complex and variable behavioural repertoire that consists of attraction, ultrasonic vocalization and urinary scent marking, and also serves as a reinforcer in learning paradigms. We identify a genetically determined circuit—extending from the accessory olfactory bulb to the posterior medial amygdala—that is necessary for all behavioural responses to darcin. Moreover, optical activation of darcin-responsive neurons in the medial amygdala induces both the innate and the conditioned behaviours elicited by the pheromone. These neurons define a topographically segregated population that expresses neuronal nitric oxide synthase. We suggest that this darcin-activated neural circuit integrates pheromonal information with internal state to elicit both variable innate behaviours and reinforced behaviours that may promote mate encounters and mate selection. A neural circuit activated by the male pheromone, darcin, mediates a complex and variable array of innate and reinforced behaviours that may promote mate encounters and mate selection.

The microbiome of mammalian scent glands is thought to contribute to the production of odorant compounds involved in sensory communication. Yet, the extent to which glandular microbiomes contain bacteria relevant to odor production and vary by host species, scent marking behavior, or gland morphology remains poorly understood, particularly in wild animals. We sampled microbes collected from skin swabs of suprapubic and sternal scent glands in wild Peruvian saddleback tamarins ( Leontocebus weddelli ; n = 19) and emperor tamarins ( Tamarinus imperator ; n = 20) to better understand glandular microbial communities. We aimed to: (1) profile glandular microbiomes of both species, focusing on odor‐related taxa and metabolic pathways, and (2) determine whether suprapubic glands, more often in contact with the external environment, had higher diversity and distinct composition of odor‐related taxa and pathways compared to sternal glands. We generated metagenomic reads using short‐read DNA shotgun sequencing from glandular swabs. We identified 18 odor‐associated microbial taxa in both tamarin species, mainly Staphylococcus and Corynebacterium , and 26 pathways, including pyruvate fermentation and amino acid metabolism. Suprapubic glands had lower Shannon alpha diversity relative to sternal glands, especially in L. weddelli . The glands of L. weddelli also differed in taxonomic composition, with odor‐related taxa more abundant in suprapubic glands. Our results provide evidence for the involvement of scent gland microbiomes in host communication biology. Glandular specializations differed not only between closely related tamarin species but also between gland types within the same individuals, suggesting a nuanced pattern of host–microbe coevolution that may shape interactions important for olfactory communication.

Mammalian chemosignals—or scent marks—are characterized by astounding chemical diversity, reflecting both complex biochemical pathways that produce them and rich information exchange with conspecifics. The microbiome of scent glands was thought to play prominent role in the chemical signal synthesis, with diverse microbiota metabolizing glandular products to produce odorants that may be used as chemosignals. Here, we use gas chromatography–mass spectrometry and metagenomic shotgun sequencing to explore this phenomenon in the anogenital gland secretions (AGS) of the giant panda (Ailuropoda melanoleuca). We find that this gland contains a diverse community of fermentative bacteria with enzymes that support metabolic pathways (e.g., lipid degradation) for the productions of volatile odorants specialized for chemical communication. We found quantitative and qualitative differences in the microbiota between AGS and digestive tract, a finding which was mirrored by differences among chemical compounds that could be used for olfactory communication. Volatile chemical compounds were more diverse and abundant in AGS than fecal samples, and our evidence suggests that metabolic pathways have been specialized for the synthesis of chemosignals for communication. The panda’s microbiome is rich with genes coding for enzymes that participate in the fermentation pathways producing chemical compounds commonly deployed in mammalian chemosignals. These findings illuminate the poorly understood phenomena involved in the role of symbiotic bacteria in the production of chemosignals.

Chemical communication plays many key roles in mammalian reproduction, although attention has focused particularly on male scent signalling. Here, we review evidence that female chemical signals also play important roles in sexual attraction, in mediating reproductive competition and cooperation between females, and in maternal care, all central to female reproductive success. Female odours function not only to advertise sexual receptivity and location, they can also have important physiological priming effects on male development and sperm production. However, the extent to which female scents are used to assess the quality of females as potential mates has received little attention. Female investment in scent signalling is strongly influenced by the social structure and breeding system of the species. Although investment is typically male-biased, high competition between females can lead to a reversed pattern of female- biased investment. As among males, scent marking and counter-marking are often used to advertise territory defence and high social rank. Female odours have been implicated in the reproductive suppression of young or subordinate females across a range of social systems, with females of lower competitive ability potentially benefiting by delaying reproduction until conditions are more favourable. Further, the ability to recognise individuals, group members and kin through scent underpins group cohesion and cooperation in many social species, as well as playing an important role in mother-offspring recognition. However, despite the diversity of female scent signals, chemical communication in female mammals remains relatively understudied and poorly understood. We highlight several key areas of future research that are worthy of further investigation.

While sociality is known to mediate territorial processes, it is less clear how sociality interacts with environmental features and neighbors' location to influence habitat selection and behavior. Scent marking, a fundamental behavior in maintaining territories, can be utilized by receiving conspecifics to evaluate both encounter risk and competitive ability of the depositing individual or group. African wild dog packs were followed in the field across 2010–2021, where researchers recorded individual behaviors and pack composition, including scent marking behaviors. We combined this historical and unique behavioral dataset with co‐occurring GPS collar data to make inferences on territorial behaviors, sociality, and habitat selection across spatial scales. We performed three analyses to determine (1) the relative probability of scent mark placement, (2) the probability of scent marking, and (3) the trade‐off strategy between scent marking and hunting, as predicted by habitat, neighbors' territories, and pack social composition. Specifically, we used resource selection function frameworks to determine how and whether conspecifics influenced habitat selection and behavior at multiple orders of selection. We found that conspecifics were influential across all three analyses, and mediated the impact of habitat on scent mark placement and probability. Scent mark placement and probability were both influenced by the social composition of packs, specifically pup presence, pack size, and number of overlapping neighbors, while pack size and pack experience influenced territorial maintenance strategy. Our findings demonstrate the importance of social structure across scales of territorial processes, from larger scale habitat selection to the probability of a behavior. We demonstrate how key behavioral theories underpinning territoriality function at the scale of habitat selection and behavioral decision‐making in a free‐ranging, large carnivore. Future research should continue to incorporate sociality in understanding the habitat selection of animals. Using a unique set of near‐continuous behavioral observations of free‐ranging wild dog packs, we combine field data with GPS locations to make inferences on how sociality mediates territorial strategies in a large carnivore. By investigating habitat selection across territorial behaviors, we make multi‐scale inferences on how inter‐ and intra‐pack structures mediate territorial maintenance.