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Communication requires both signals and receiver responses, yet we know little about how signals and responses covary when recognition capacity differs across a species' geographical range. Previous work has shown that Polistes fuscatus wasps from Michigan, U.S.A. are capable of individual face recognition, while P. fuscatus from central Pennsylvania, U.S.A. are not. Here, we provide a broader assessment of intraspecific variation in signals and responses across the range of P. fuscatus. We quantify the amount of perceivable facial pattern variation in each population as a measure of individual identity signalling. We also measure how accurately wasps from each population learn to discriminate between a standard set of conspecific faces as a measure of individual face recognition. We show that wasps are equally adept at learning to discriminate faces of wasps from their own population and faces of wasps from different populations, confirming that discriminating a standard set of faces provides a comparable measure of individual face learning capacity. We find that there is striking variation in signals and responses across wasp populations and that individual identity signals and receiver responses are linked. Wasps from populations with more variable individual identity signals learn to discriminate between a standard set of conspecific faces more accurately than wasps from populations with less variable individual identity signals. Overall, we find surprisingly high levels of intraspecific geographical variation in individual identity signals and responses. Work in additional taxa will be important to assess whether signal phenotype and receiver responses are commonly linked in geographically variable communication systems. • Paper wasps have a geographically variable communication system. • Both individual identity signals and individual recognition varied across populations. • Wasps discriminated faces of wasps from their own and different populations. • Some populations with variable facial patterns were capable of individual recognition. • Populations that lacked variable facial patterns did not recognize individuals. [ABSTRACT FROM AUTHOR]

Individual recognition is an important element of social interactions among animals. While the presence of individually distinct vocalisations (providing a basis for individual recognition) has been widely tested across species, information about which components of a call encode this information is lacking. We investigated whether female alpaca (Vicugna pacos) vocalisations, particularly their hums, encode information about individual identity and explored which parameters contribute to this encoding. We recorded vocalisations from 9 adult female alpaca and extracted both spectro-temporal features (frequencies and duration) and mel-frequency cepstral coefficients (MFCC). Random forest analyses revealed clear individual differences in both datasets, with the spectro-temporal features allowing for slightly more accurate classification than MFCC (71% and 66.5% accuracy for spectro-temporal features and MFCC, respectively). These robust acoustic identities have the potential to provide a basis for individual recognition in alpaca, which could have important flow-on effects for alpaca communication, as it allows receivers to modulate their response to the callers' identity. Alpaca, as herd-living and vocal animals, provide an excellent model system for better understanding the mechanisms, causes and consequences of recognition and inter-individual communication. [ABSTRACT FROM AUTHOR]

Social isolation often has lasting negative effects on social behavior, but less research has tested how the timing of isolation influences its effects. Some behaviors have a sensitive period where experience has particularly strong effects, while other behaviors are more flexible. Here, we test how the timing of social experience influences the development of individual face learning in Polistes fuscatus wasps. Individual face recognition is a key aspect of communication in wasps, so wasps reared in a typical environment are adept at individual face learning. We reared wasps in 5 treatments that differed in the timing and amount of social experience: 14 days isolation, 14 days nest, 7 days nest, 7 days nest then 7 days isolation, and 7 days isolation then 7 days nest. Then, we tested individual face learning. Experience with conspecifics improved individual face learning, but the timing of experience did not impact performance. Wasps reared in normal social environments were adept at learning and remembering faces, while isolated wasps were unable to learn and remember faces. Early isolation did not have a stronger effect than later isolation, indicating that there is no early sensitive period for face learning in paper wasps. Instead, paper wasps exhibit a high level of plasticity in the development of individual face learning. Overall, this work emphasizes the role of plasticity in the development of complex social recognition and offers insight into the conditions where evolution favors high plasticity over rigid sensitive periods in development. Significance: Animal behavior is influenced by experience during development. In some cases, the timing of an experience is important. In other cases, development is flexible such that experiences at any time have similar effects on behavioral development. We alter the amount and timing of social experience in wasps to test whether wasps have an early sensitive period where social experience has a particularly strong effect on capacity for individual face learning. We find that social experience improves wasps' ability to learn and remember the unique faces of other wasps, but the timing of experience doesn't influence performance. Wasps isolated early and late in life perform similarly. Therefore, early social experience is not necessary for individual face learning. [ABSTRACT FROM AUTHOR]

Because climate change and the biodiversity crisis are driven by human actions, determining psychological mechanisms underpinning support for environmental action is an urgent priority. Here, we experimentally tested for mechanisms promoting conservation-related motivation and behavior toward a flagship species, wild Tamanend's bottlenose dolphins. Following evidence that empathy increases prosocial motivations and behavior, and that the ability to identify individual humans promotes empathy, we tested whether this relationship applied to the ability to identify individual dolphins. Participants identified dolphins from their dorsal fins at above chance levels, and better individuation correlated with higher empathy for dolphins and higher willingness to pledge environmental behaviors. Pairing a narrative with an image of an injured dolphin leads to higher donations relative to a narrative alone. Our novel finding that the ability to individually identify dolphins relates to empathy and conservation-related behavior suggests pathways for strengthening environmental attitudes and behavior. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China Agricultural University is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Simple Summary: Accurate identification of individual Amur tigers is vital for their conservation, as it helps us understand their population and distribution. Existing identification methods often fall short in accuracy, and our study focuses on creating a more accurate method for identifying individual Amur tigers using advanced deep learning techniques. We improved an existing neural network model called InceptionResNetV2 by adding features like dropout layers and dual-attention mechanisms to better capture the unique stripe patterns of each tiger and reduce errors during training. We tested our model on a large dataset of tiger images and found it to be highly effective, achieving an average recognition accuracy of over 95% for different body parts, with left stripes reaching the highest 99.37%. This method significantly outperforms previous models and provides a reliable tool for wildlife researchers and conservationists to monitor and protect Amur tigers. By improving the ability to track individual tigers, our research offers practical benefits for preserving this endangered species and enhancing wildlife management practices globally. Accurate and intelligent identification of rare and endangered individuals of flagship wildlife species, such as Amur tiger (Panthera tigris altaica), is crucial for understanding population structure and distribution, thereby facilitating targeted conservation measures. However, many mathematical modeling methods, including deep learning models, often yield unsatisfactory results. This paper proposes an individual recognition method for Amur tigers based on an improved InceptionResNetV2 model. Initially, the YOLOv5 model is employed to automatically detect and segment facial, left stripe, and right stripe areas from images of 107 individual Amur tigers, achieving a high average classification accuracy of 97.3%. By introducing a dropout layer and a dual-attention mechanism, we enhance the InceptionResNetV2 model to better capture the stripe features of individual tigers at various granularities and reduce overfitting during training. Experimental results demonstrate that our model outperforms other classic models, offering optimal recognition accuracy and ideal loss changes. The average recognition accuracy for different body part features is 95.36%, with left stripes achieving a peak accuracy of 99.37%. These results highlight the model's excellent recognition capabilities. Our research provides a valuable and practical approach to the individual identification of rare and endangered animals, offering significant potential for improving conservation efforts. [ABSTRACT FROM AUTHOR]

Many social animals can recognize other individuals by their vocalizations. This requires a memory system capable of mapping incoming acoustic signals to one of many known individuals. Using the zebra finch, a social songbird that uses songs and distance calls to communicate individual identity (Elie and Theunissen, 2018), we tested the role of two cortical-like brain regions in a vocal recognition task. We found that the rostral region of the Cadomedial Nidopallium (NCM), a secondary auditory region of the avian pallium, was necessary for maintaining auditory memories for conspecific vocalizations in both male and female birds, whereas HVC (used as a proper name), a premotor areas that gates auditory input into the vocal motor and song learning pathways in male birds (Roberts and Mooney, 2013), was not. Both NCM and HVC have previously been implicated for processing the tutor song in the context of song learning (Sakata and Yazaki-Sugiyama, 2020). Our results suggest that NCM might not only store songs as templates for future vocal imitation but also songs and calls for perceptual discrimination of vocalizers in both male and female birds. NCM could therefore operate as a site for auditory memories for vocalizations used in various facets of communication. We also observed that new auditory memories could be acquired without intact HVC or NCM but that for these new memories NCM lesions caused deficits in either memory capacity or auditory discrimination. These results suggest that the high-capacity memory functions of the avian pallial auditory system depend on NCM.SIGNIFICANCE STATEMENT Many aspects of vocal communication require the formation of auditory memories. Voice recognition, for example, requires a memory for vocalizers to identify acoustical features. In both birds and primates, the locus and neural correlates of these high-level memories remain poorly described. Previous work suggests that this memory formation is mediated by high-level sensory areas, not traditional memory areas such as the hippocampus. Using lesion experiments, we show that one secondary auditory brain region in songbirds that had previously been implicated in storing song memories for vocal imitation is also implicated in storing vocal memories for individual recognition. The role of the neural circuits in this region in interpreting the meaning of communication calls should be investigated in the future.

Signals and receiver responses often vary across a species' geographic range. Effective communication requires a match between signal and receiver response, so there is much interest in the developmental mechanisms that maintain this link. Two potential mechanisms are genetic covariance between signal and receiver response and plasticity where individuals adjust their phenotype based on their partner's phenotype. Here, we test how plasticity contributes to geographic variation in individual face recognition in Polistes fuscatus wasps. Previous work has shown that P. fuscatus from Michigan, USA (MI) have variable facial patterns used for individual recognition, while P. fuscatus from central Pennsylvania, USA (PA) lack variable facial patterns and are unable to learn individual conspecifics. We experimentally altered rearing environment, so wasps were either reared with their own population or in a common garden with wasps from both populations. Then, we tested the wasps' capacity to learn and remember individual conspecific faces. Consistent with previous work, MI wasps reared with MI wasps were adept at learning conspecific faces, while PA wasps reared with PA wasps were unable to learn conspecific faces. However, MI and PA wasps reared in a common garden developed similar, intermediate capacity for individual face learning. These results indicate that individual face learning in Polistes wasps is highly plastic and responsive to the social environment. Plasticity in receiver responses may be a common mechanism mediating geographic differences in non-sexual signaling systems and may play a role in maintaining links between signals and receiver responses in geographically variable communication systems. [ABSTRACT FROM AUTHOR]

Birds are known to be highly social and visual animals. Yet no specific visual feature has been identified to be responsible for individual recognition in birds. Here, using a differential looking paradigm across five experiments, we demonstrated that African penguins, Spheniscus demersus, spontaneously discriminated between life-size photographs of their monogamous, lifelong partner and a nonpartner colonymate using their ventral dot patterns. Our findings challenge the assumption of limited visual involvement in penguin communication and suggest a rather complex and flexible recognition process in these birds. The combination of our current results and previous findings, which showed cross-modal (visual/auditory) recognition in these animals, suggests that African penguins use their ventral dot patterns to individually recognize their colonymates. Our results provide the first evidence of a specific visual cue responsible for spontaneous individual recognition by a bird, and highlight the importance of considering all sensory modalities in the study of animal communication. • African penguins spontaneously recognize their partner visually. • Penguins rely strongly on their ventral dot patterns for individual recognition. • Penguins may have holistic representations of other penguins. • We challenge the idea of a limited visual involvement in penguins' communications. • Results suggest a complex and flexible recognition system in African penguins. [ABSTRACT FROM AUTHOR]

Members of several shoaling species have been shown to prefer to associate with familiar individuals, enhancing the benefits of aggregation. The authors used a series of social preference tasks in the laboratory to evaluate whether prior familiarity with potential partners influences preference of shoaling partner in male zebrafish (Danio rerio), a social species found in shallow, slow-moving waters. The authors found that though male zebrafish exhibited a strong preference for shoaling with a male conspecific as opposed to remaining alone, they exhibited no preference for familiar over unfamiliar conspecifics. This suggests that the benefits of familiarity for shoaling behaviour may not be as important for male zebrafish as has been shown in other social fish species.

Accurate and intelligent identification of rare and endangered individuals of flagship wildlife species, such as Amur tiger (Panthera tigris altaica), is crucial for understanding population structure and distribution, thereby facilitating targeted conservation measures. However, many mathematical modeling methods, including deep learning models, often yield unsatisfactory results. This paper proposes an individual recognition method for Amur tigers based on an improved InceptionResNetV2 model. Initially, the YOLOv5 model is employed to automatically detect and segment facial, left stripe, and right stripe areas from images of 107 individual Amur tigers, achieving a high average classification accuracy of 97.3%. By introducing a dropout layer and a dual-attention mechanism, we enhance the InceptionResNetV2 model to better capture the stripe features of individual tigers at various granularities and reduce overfitting during training. Experimental results demonstrate that our model outperforms other classic models, offering optimal recognition accuracy and ideal loss changes. The average recognition accuracy for different body part features is 95.36%, with left stripes achieving a peak accuracy of 99.37%. These results highlight the model’s excellent recognition capabilities. Our research provides a valuable and practical approach to the individual identification of rare and endangered animals, offering significant potential for improving conservation efforts.

Individual recognition underlies social behaviors in many species and is essential for complex social interactions commonly occurring between conspecifics. Focusing on visual perception, we explored this process in African grey parrots (Psittacus erithacus) using the matching-to-sample (MTS) method commonly used in primate research. We used cards made from photographs of familiar conspecific in four consecutive experiments, first testing the ability of our subjects (two male and one female adult) to match the photographs of familiar individuals and then creating modified stimuli cards to determine which visual aspects and features were crucial for successful recognition of a familiar conspecific. All three subjects were able to successfully match different photographs of familiar conspecifics in Experiment 1. Experiments 2-4 showed that modification of the facial area in the photograph had only a weak effect on subjects' success rates in MTS tasks. On the other hand, changes in the plumage color or obscuring of abdominal cues impaired their ability to successfully match conspecifics' photographs in some tasks. This study implies that African grey parrots process visual information holistically. Moreover, the process of individual recognition in this species differs from what we find in primates, including humans, where faces play a crucial role. [ABSTRACT FROM AUTHOR]

Milk production plays an essential role in the global economy. With the development of herds and farming systems, the collection of fine-scale data to enhance efficiency and decision-making on dairy farms still faces challenges. The behavior of animals reflects their physical state and health level. In recent years, the rapid development of the Internet of Things (IoT), artificial intelligence (AI), and computer vision (CV) has made great progress in the research of precision dairy farming. Combining data from image, sound, and movement sensors with algorithms, these methods are conducive to monitoring the behavior, health, and management practices of dairy cows. In this review, we summarize the latest research on contact sensors, vision analysis, and machine-learning technologies applicable to dairy cattle, and we focus on the individual recognition, behavior, and health monitoring of dairy cattle and precise feeding. The utilization of state-of-the-art technologies allows for monitoring behavior in near real-time conditions, detecting cow mastitis in a timely manner, and assessing body conditions and feed intake accurately, which enables the promotion of the health and management level of dairy cows. Although there are limitations in implementing machine vision algorithms in commercial settings, technologies exist today and continue to be developed in order to be hopefully used in future commercial pasture management, which ultimately results in better value for producers. [ABSTRACT FROM AUTHOR]

In humans, identity is partly encoded in a voice-print that is carried across multiple vocalizations. Other species also signal vocal identity in calls, such as shown in the contact call of parrots. However, it remains unclear to what extent other call types in parrots are individually distinct, and whether there is an analogous voice-print across calls. Here we test if an individual signature is present in other call types, how stable this signature is, and if parrots exhibit voice-prints across call types. We recorded 5599 vocalizations from 229 individually marked monk parakeets (Myiopsitta monachus) over a 2-year period in Barcelona, Spain. We examined five distinct call types, finding evidence for an individual signature in three. We further show that in the contact call, while birds are individually distinct, the calls are more variable than previously assumed, changing over short time scales (seconds to minutes). Finally, we provide evidence for voice-prints across multiple call types, with a discriminant function being able to predict caller identity across call types. This suggests that monk parakeets may be able to use vocal cues to recognize conspecifics, even across vocalization types and without necessarily needing active vocal signatures of identity.

Previous research has shown that African jewel fish (Hemichromis bimaculatus) recognize pair-bonded mates during their exchanges of egg-guarding duties. The current research examined the perceptual cues for face recognition by comparing two face models displaying anatomically realistic arrangements of blue iridophores derived from discriminant function analysis of distinct sibling groups. Four groups each consisting of 9 subadults were examined using a narrow compartment restraining lateral movement where face models were presented at eye level for eight trials. Because respiratory movement of the operculum can mechanically displace the eye thereby shifting the retinal image, jewel fish reduce their respiration rate during increased attention. When two experimental groups were presented with the same face models on four trials following initial model presentations, both groups exhibited stable respiration rates indicative of model habituation. When the habituated face models were switched to novel face models on the fifth trial, the rates of respiration decreased as measured by reliable increases in the elapsed times of opercular beats. Switching the models back to the habituated models on the sixth trial caused reliable decreases in the elapsed times of opercular beats, resembling the earlier trials for the habituated models. Switching the face models again to the formerly novel models on the seventh trial produced respiration rates that resembled those of the habituated models. The two control groups viewing the same models for all eight trials exhibited no substantial change in respiration rates. Together, these findings indicate that jewel fish can learn to recognize novel faces displaying unique arrangements of iridorphores after one trial of exposure. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To study individual recognition in animals, discrimination tasks are often conducted by presenting 2D images of real conspecifics. However, animals may discriminate the images merely as visual stimulus combinations without establishing referential relationships to the individuals depicted. In the current study, we investigated whether goats are able to discriminate photos of familiar and unfamiliar conspecifics, whether they not only process the photos as visual stimuli, but also understand them as virtual copies of real conspecifics and whether they grasp the concept of familiarity. Using a computer-controlled learning device, in three tests, goats of two experimental groups (A and B) had to discriminate portrait (Te1), profile (Te2) or headless body photos (Te3) of conspecifics. Tests were presented as 4-choice tasks, with one photo from Group A (rewarded) plus three photos from Group B (distractors). That is, the rewarded photo was familiar to Group A, but unfamiliar to Group B. Finally, in a reversal test (Te4) we reversed this principle. The goats learned the discriminations in Te1 to Te3 within two (Te1 and Te2) and three training days (Te3), respectively, and they needed between 91 [CL (66, 126)] and 174 [CL (126, 241)] trials to reach the learning criterion, with no statistically significant differences between the groups. In Te4, in contrast, the animals took 403 [Group A; CL (291, 557)] and 385 [Group B; CL (286, 519)] trials, respectively, to learn the task. The lack of spontaneous preferences for the photo of the familiar conspecific in the pretests of Te1 to Te3 in Group A, as well as the lack of differences in the number of trials to learn the discriminations between both groups, do not at first glance suggest that the goats established a correspondence between real conspecifics and their 2D representations. However, the higher number of trials in Te4 suggests that both groups formed the learning rule of choosing either the known (Group A) or the unknown goat (Group B) over the course of Te1 to Te3 and then failed after the rule was reversed, providing evidence that goats can associate 2D photos of conspecifics with real animals. [ABSTRACT FROM AUTHOR]

Population monitoring is a crucial method for conservation projects, especially for the highly endangered clade of amphibians which is threatened by habitat loss and emerging infectious diseases such as the chytrid fungus Batrachochytrium salamandrivorans (Bsal). Bsal has led to massive population declines of European fire salamanders in Belgium, the Netherlands and parts of Germany and population trends are decreasing. Thus, regular population monitoring is essential to keep track of population dynamics and detect potential Bsal outbreaks, especially since valid population estimates for many species and/or populations are scarce. In recent years, photographic mark-recapture studies have gained importance enabling researchers to keep track of individuals without the use of harmful marking techniques that might influence behaviour or survival. We monitored a European fire salamander population over four years in the Kottenforst forest, Germany, by combining a mark-recapture approach with a new photo-recognition software, the Amphibian and Reptile Wildbook. We investigated potential differences of two ecotypes, i.e., larval populations bred in ponds and streams. Furthermore, we compared the observed number of larvae and the estimated population sizes between two consecutive years. There was a year effect on the observed number of larvae, the percentage of injured larva and estimated population size. The habitat type affected apparent survival rates. There was also a habitat effect on the percentage of injured larvae, but this was only existent in some years. The mean larval size, water temperature and the superpopulation size were not affected by any of the aforementioned factors. Although the population was free from Bsal, the high variation in the population estimates emphasize the need for a regular and standardised monitoring to assess the current population status and detect early population declines that might otherwise remain overlooked. [ABSTRACT FROM AUTHOR]

Social toothed whales are known to produce specific vocalizations that may serve for individual or group recognition and maintaining cohesion among group members. In beluga whales Delphinapterus leucas, these vocalizations referred to as "contact calls" are relatively long duration, repeated stereotyped broadband sounds. Although these calls are thought to be critical in mother‐calf communication, they are utilized by individuals of different ages and sex. We investigated possible occurrence of contact calls in all‐male beluga groups from the White Sea, Russia. Among the vocalizations analyzed (n = 1169), a considerable proportion (58%) appeared to be potential contact calls. They were subjectively classified into 61 types of mostly complex broadband sounds combined with a narrow band element. The positive linear relationship (R2 = 0.90) between the number of unique call types identified in the recordings and the number of belugas observed in the research area suggests that the calls serve as individual signatures. Belugas tended to produce these calls in a series, with the intercall intervals between the same and different call types mainly >1 s and <1 s, respectively. This suggests that vocal exchange by individually distinctive calls, like those of captive belugas and some other social species, might take place. The current study provides more insight into contact call usage in wild belugas and may serve as a basis for long‐term monitoring of their seasonal occurrence, abundance, and site fidelity, as well as for investigating their social organization. [ABSTRACT FROM AUTHOR]

The way a person walks has unique characteristics for each individual and can be used to recognize them. There are various ways to classify characteristics for gait of each individual, one of them is the inertia sensor. The inertia sensor is used to collect data gait signals, which are angular velocity variations caused by human walking movements. Multidistance Signal Level Difference Sample Entropy is proposed in this study as a feature extraction before classifying individual gaits. MSLD is used to measure the co-occurrence of two signal samples at a distance d, and SampEn quantizes signal complexity. The MSLD Entropy produce 60 features in the form of SampEn at distances of 1 until 20 from the threeaxis. The testing procedure is carried out on the MSLD Entropy result signal for each classifier with a feature in the form of SampEn at distances of d=1-20, d=1-15, d=1-10, and d=1-5. Softmax regression as a classifier and feature at distance 1 until 20, the test results produce the greatest accuracy of 98.3%. Because a person's gait can be identified not just from one but three directions, using only one axis results in lesser accuracy than using data from all three axes. [ABSTRACT FROM AUTHOR]

To study individual recognition in animals, discrimination tasks are often conducted by presenting 2D images of real conspecifics. However, animals may discriminate the images merely as visual stimulus combinations without establishing referential relationships to the individuals depicted. In the current study, we investigated whether goats are able to discriminate photos of familiar and unfamiliar conspecifics, whether they not only process the photos as visual stimuli, but also understand them as virtual copies of real conspecifics and whether they grasp the concept of familiarity. Using a computer-controlled learning device, in three tests, goats of two experimental groups (A and B) had to discriminate portrait (Te1), profile (Te2) or headless body photos (Te3) of conspecifics. Tests were presented as 4-choice tasks, with one photo from Group A (rewarded) plus three photos from Group B (distractors). That is, the rewarded photo was familiar to Group A, but unfamiliar to Group B. Finally, in a reversal test (Te4) we reversed this principle. The goats learned the discriminations in Te1 to Te3 within two (Te1 and Te2) and three training days (Te3), respectively, and they needed between 91 [CL (66, 126)] and 174 [CL (126, 241)] trials to reach the learning criterion, with no statistically significant differences between the groups. In Te4, in contrast, the animals took 403 [Group A; CL (291, 557)] and 385 [Group B; CL (286, 519)] trials, respectively, to learn the task. The lack of spontaneous preferences for the photo of the familiar conspecific in the pretests of Te1 to Te3 in Group A, as well as the lack of differences in the number of trials to learn the discriminations between both groups, do not at first glance suggest that the goats established a correspondence between real conspecifics and their 2D representations. However, the higher number of trials in Te4 suggests that both groups formed the learning rule of choosing either the known (Group A) or the unknown goat (Group B) over the course of Te1 to Te3 and then failed after the rule was reversed, providing evidence that goats can associate 2D photos of conspecifics with real animals.

Visual individual recognition requires animals to distinguish among conspecifics based on appearance. Though visual individual recognition has been reported in a range of taxa including primates, birds, and insects, the features that animals require to discriminate between individuals are not well understood. Northern paper wasp females, Polistes fuscatus, possess individually distinctive color patterns on their faces, which mediate individual recognition. However, it is currently unclear what role color plays in the facial recognition system of this species. Thus, we sought to test two possible roles of color in wasp facial recognition. On one hand, color may be important simply because it creates a pattern. If this is the case, then wasps should perform similarly when discriminating color or grayscale images of the same faces. Alternatively, color itself may be important for recognition of an image as a "face", which would predict poorer performance on grayscale discrimination relative to color images. We found wasps performed significantly better when discriminating between color faces compared to grayscale versions of the same faces. In fact, wasps trained on grayscale faces did not perform better than chance, indicating that color is necessary for the recognition of an image as a face by the wasp visual system. [ABSTRACT FROM AUTHOR]

The behaviour of the tompot blenny Parablennius gattorugine was studied by underwater observation and photography on the south‐west coast of the UK over an 11 year period, with >50 individuals identified at two locations by their distinctive skin markings. Observations showed males engaging in rapid swimming behaviour when approached by a female, and younger males using alternative 'sneaker' tactics before becoming 'bourgeois' territory‐holders. The noninvasive recognition technique also facilitated detailed observations on territory retention (up to 7 years) and agonistic behaviours among both males and females. [ABSTRACT FROM AUTHOR]

Dairy cow face recognition using Neural Networks has several hurdles. For example, there are only a few instances of each individual. The positions and angles of the individuals in the image fluctuate considerably, the differences between individuals are not apparent, and the number of individuals that the network has not been trained on is enormous, etc. In this paper, an enhanced Siamese Neural Network is used to overcome these barriers. First, a combination of Dense Block (DB) and Capsule Network is employed as a feature extractor to keep the spatial information of features while expanding the feature extraction capabilities of the Convolutional Neural Network. Second, image pairings are processed through the Siamese Neural Network to obtain bivariate features. Finally, image recognition is achieved via the correlation analysis of bivariate features. We conduct comparison experiments with different networks on a small cow face dataset. The experimental results demonstrate that Siamese DB Capsule Network can learn abstract knowledge about distinct individuals and can be extended to unfamiliar cows for zero-shot learning.

The Cape fur seal (Arctocephalus pusillus pusillus) is one of the most colonial mammal species in the world. Females exclusively nurse their pups for 9 to 11 months, during which they alternate frequent foraging trips at sea with suckling periods ashore. The survival of the pup thus depends on the ability of the mother–pup pair to relocate each other among thousands of individuals. Previous work has demonstrated identity information encoded in pup-attraction (PAC) and female-attraction (FAC) calls. Here, we investigated vocal recognition between mother and pup using playbacks of PAC and FAC performed during the breeding season at Pelican Point, Namibia. Both females and pups were able to specifically discriminate the voice of their pup or their mother from non-affiliated pup or mother. Females were able to memorize previous versions of their pup's calls (evidence of recognition up to 73 days after pup's calls recording). Vocal recognition was demonstrated in pups from 1- to 13-weeks old age. Females and pups did not respond differently to the non-filial or non-mother (for pups) stimulus even if it had a strong acoustic similarity with the filial or mother stimulus. This suggested that Cape fur seal mother–pup pairs have high perceptual and cognitive abilities, allowing individuals to identify kin's vocalizations in a very noisy and confusing environment. [ABSTRACT FROM AUTHOR]

Investigation of individual recognition (IR) is difficult due to the lack of proper control of cues and previous experiences of subjects. Utilization of artificial agents (Unidentified Moving Objects: UMOs) may offer a better approach than using conspecifics or humans as partners. In Experiment 1, we investigated whether dogs are able to develop IR of UMOs (that is stable for at least 24 h) or that they only retain a more generalised memory about them. The UMO helped dogs to obtain an unreachable ball and played with them. One day, one week or one month later, we tested whether dogs display specific behaviour toward the familiar UMO over unfamiliar ones (four-way choice test). Dogs were also re-tested in the same helping context and playing interaction. Subjects did not approach the familiar UMO sooner than the others; however, they gazed at the familiar UMO earlier during re-testing of the problem solving task, irrespectively of the delay. In Experiment 2, we repeated the same procedure with human partners, applying a two-way choice test after a week delay, to study whether lack of IR was specific to the UMO. Dogs did not approach the familiar human sooner than the unfamiliar, but they gazed at the familiar partner earlier during re-testing. Thus, dogs do not seem to recognise an individual UMO or human after a short experience, but they remember the interaction with the novel partner in general, even after a long delay. We suggest that dogs need more experience with a specific social partner for the development of long-term memory. [ABSTRACT FROM AUTHOR]

Early social experience has lasting effects on adult social interactions, but less is known about how and why experience impacts social behavior. One way experience may alter adult behavior is by affecting the development of communication. Here, we test how early experience impacts individual face learning, a key aspect of communication in Polistes fuscatus wasps. We reared P. fuscatus workers in five social environments: with conspecifics, alone with a mirror, alone with a wasp visible through glass, alone with pictures of P. fuscatus, and completely alone. Then, we tested the wasps' ability to learn and remember individual conspecifics. We found that experience with conspecifics improved wasps' capacity for individual face learning. Wasps reared in normal social environments were adept at learning and remembering faces, while isolated wasps and wasps exposed to only pictures were unable to learn faces. Notably, even limited social experience improved face learning, as wasps exposed to a mirror or a conspecific through glass had intermediate capacity for learning faces. Thus, the development of individual face learning is strongly influenced by the type and amount of early social experience. Although the development of many aspects of behavior requires little experience, behaviors like individual recognition may depend on consistent social interactions. Significance statement: Individual face learning is a challenging task that requires organisms to learn and remember the unique faces of others. Developing the capacity for individual face learning may require extensive social experience, but little work has evaluated the amounts and types of experience needed. Here, we show that the type and amount of social experience influences individual face learning. Wasps with more social experience are better able to learn faces than wasps with less social experience. Surprisingly little social experience is sufficient, as wasps that viewed a single individual without any direct social contact were able to discriminate individual conspecific face more accurately than wasps reared alone. In the wild, animals may experience a range of different social environments, so there is much room for future work exploring how experience influences animal communication and recognition. [ABSTRACT FROM AUTHOR]

In the aging process of normal people, the functional activity pattern of brain is in constant change, and the change of brain runs through the whole life cycle, which plays a crucial role in the track of individual development. In recent years, some studies had been carried out on the brain functional activity pattern during individual aging process from different perspectives, which provided an opportunity for the problem we want to study. In this study, we used the resting-state functional magnetic resonance imaging (rsfMRI) data from Cambridge Center for Aging and Neuroscience (Cam-CAN) database with large sample and long lifespan, and computed the functional connectivity (FC) values for each individual. Based on these values, the hemispheric similarity of functional connectivity (HSFC) obtained by Pearson correlation was used as the starting point of this study. We evaluated the ability of individual recognition of HSFC in the process of aging, as well as the variation trend with aging process. The results showed that HSFC could be used to identify individuals effectively, and it could reflect the change rule in the process of aging. In addition, we observed a series of results at the sub-module level and find that the recognition rate in the sub-module was different from each other, as well as the trend with age. Finally, as a validation, we repeated the main results by human brainnetome atlas (BNA) template and without global signal regression, found that had a good robustness. This also provides a new clue to hemispherical change patterns during normal aging. [ABSTRACT FROM AUTHOR]

Under natural conditions, foals stop nursing from their dam at approximately-9 months old, but their bond persists until 1.5–2.5 years of age. In contrast, in horse breeding, foals are generally artificially weaned and totally separated from their dam at 5–7 months. However, it is not known whether the bond between the dam and her foal is maintained after artificial weaning. The aim of this study was (1) to assess whether foals still recognise and prefer their dam over other familiar mares several months after weaning and (2) to evaluate whether the preference for the dam is more pronounced in fillies or colts. Fifteen fillies and 19 colts were weaned at the age of 7 months old (complete separation from the mother). At the age of one year (i.e., 5 months after the separation), they underwent a test evaluating their preference for their dam or a familiar mare from their natal group. Significantly more foals first approached their dam; they also sniffed and tended to look more often at her. This finding indicates that artificially weaned horses remember and still exhibit a preference for their dam, suggesting that the bond persists even after 5 months of separation. Moreover, fillies exhibited a stronger preference for both mares than colts: they looked at them more frequently, sniffed them for a longer duration and spent more time in proximity to both mares than colts. This suggests that fillies generally have an even stronger attachment to their dam as well as to other mares from their natal group. This study calls into question the practice of artificial weaning at 5–7 months of age.

Milk production plays an essential role in the global economy. With the development of herds and farming systems, the collection of fine-scale data to enhance efficiency and decision-making on dairy farms still faces challenges. The behavior of animals reflects their physical state and health level. In recent years, the rapid development of the Internet of Things (IoT), artificial intelligence (AI), and computer vision (CV) has made great progress in the research of precision dairy farming. Combining data from image, sound, and movement sensors with algorithms, these methods are conducive to monitoring the behavior, health, and management practices of dairy cows. In this review, we summarize the latest research on contact sensors, vision analysis, and machine-learning technologies applicable to dairy cattle, and we focus on the individual recognition, behavior, and health monitoring of dairy cattle and precise feeding. The utilization of state-of-the-art technologies allows for monitoring behavior in near real-time conditions, detecting cow mastitis in a timely manner, and assessing body conditions and feed intake accurately, which enables the promotion of the health and management level of dairy cows. Although there are limitations in implementing machine vision algorithms in commercial settings, technologies exist today and continue to be developed in order to be hopefully used in future commercial pasture management, which ultimately results in better value for producers.

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Individual-based studies where animals are monitored through space and time enable explorations of ecology, demography, evolutionary biology, movements, and behavior. Here, we review 70 years of research on an endangered African herbivore, the giraffe, based on individual spot pattern recognition, and profile an example of a long-term photographic mark–recapture study of Masai giraffes in Tanzania. We illustrate how individual-based data can be used to examine the fitness consequences (variation in survival and reproduction) of extrinsic environmental factors or intrinsic traits in an evolutionary ecology framework. These data also allow the study of social structure, space use, life histories, and health. The giraffe offers an excellent opportunity to study dynamics of an ungulate species with a highly fission–fusion social system using spot pattern recognition. [ABSTRACT FROM AUTHOR]

Automatic individual recognition techniques can support data collection in the field of ethology. Recent studies have contributed to development of automatic individual recognition techniques using machine learning and deep learning. However, varied conditions in the wild, such as the presence of occlusions and head rotations of individuals, can lower the accuracy of automatic recognition techniques. Thus, there is requirement for improvement in the accuracy and robustness of these techniques. In this study, we have used previously observed information updated with given current observation by Bayesian inference to improve the automatic individual recognition of free‐ranging Japanese macaques (Macaca fuscata) at Katsuyama, Japan. We collected static images and video footage of 51 adult individuals. Using the static images, we created eight individual recognition systems (classifiers), using GoogLeNet and ResNet‐18 as convolutional neural network models. Additionally, sequential data of the faces of the macaques were obtained from 86 video recordings of the 51 individuals to evaluate the classifiers. We were able to successfully recognize 90% or more individuals with each classifier through the combination of the sequential Bayesian filter and the classifier. Eighty‐five percent or more of the individuals had posterior probabilities of 90% or above when conducting recognition tests using the sequential Bayesian filter with 10 images. The best classifier recognized 98% of individuals using 10 images and all individuals using 50 images. Recognition was also successful when the sequential Bayesian filter was applied to cases in which the recognition rate was <50% with test data when the filter was not applied. Based on the above results, we posit that the accuracy of individual recognition systems can be improved using a sequential Bayesian filter that considers past information for individuals. [ABSTRACT FROM AUTHOR]

Chemical signals, such as those used in social communication, are often present as complex blends of compounds, suggesting that complexity is important in signal perception. Very few studies, however, have examined the interactions between different components of complex signals in social signalling. In the Mysore day gecko, Cnemaspis mysoriensis , secretions of males are sufficient to elicit a behavioural response in females and these male secretions differ from those of females in the presence of two key chemical compounds: cholesterol and squalene. This provided us with an opportunity to determine the functions and interactions of individual components in a complex multicomponent chemical signal. First, using tongue flick assays, we established that both components independently elicit a behavioural response in females, but not males. When presented as a multicomponent mix, the response levels of females were similar to those shown towards the individual components, thereby indicating that cholesterol and squalene are redundant components. Moreover, female responses towards these components matched their level of response towards natural male secretions, confirming that both cholesterol and squalene signal sex identity of males. When presented with a gradient of multicomponent stimulus concentrations, females, but not males, incrementally adjusted their tongue flick responses to different levels. Further, responses of females were similar regardless of whether cholesterol or squalene was at a higher relative concentration in the multicomponent stimulus. These last two sets of results indicate that the overall concentration, but not the relative ratio of cholesterol and squalene, has the potential to encode information about male quality. Lack of responses by males to these compounds across experiments strongly indicate the role of cholesterol and squalene in intersexual, and not intrasexual, communication. Overall, we show that two sex-specific compounds in a complex multicomponent chemical signal are effective in communicating complex sexual information from males to conspecific females. • Chemical signals in males of Cnemaspis mysoriensis contain cholesterol and squalene. • Only females respond to these compounds, in ways that indicate redundancy. • Cholesterol and squalene are independently effective sex identity signals. • Dose-dependent responses indicate potential for these to be mate assessment signals. [ABSTRACT FROM AUTHOR]

Vocal communication in group-living animals represents a major challenge when multiple individuals call simultaneously and generate a complex soundscape. Decoding relevant information from a vocal signal and its emitter can determine the survival of the receiver. In hierarchical social groups, information on sex, size and age can provide relevant context for vocal signals. Ultimately, individual vocal recognition is a keystone in vocal communication systems, especially in the context of sociality. Greylag geese (Aves: Anseriformes) are a basal, gregarious and highly social species, and adults produce a distance call when approaching or leaving the flock. In this study we (1) quantified the acoustic properties of distance calls to test whether they can provide information on the sex, size and age of the emitter, (2) evaluated whether distance calls have individual properties, from the sender's perspective, (3) tested whether receivers discriminate distance calls depending on the emitter's identity and (4) explored whether an individual's response strength towards its partner's distance call is associated with fitness-related traits (i.e. pair bond duration and average number of offspring per year). We recorded distance calls of individually marked geese, quantified the variation in call acoustic properties and carried out a playback experiment in the wild. Distance calls encoded information about the sex of the goose, but not its age or size. From the emitter's perspective, we found some support for individuality in distance calls. From the receiver's perspective, geese were capable of recognizing distance calls from different individuals. Finally, the response strength towards playback of the partner's call was positively correlated with pair bond duration. Vocal recognition has been proposed to be tightly related to social structure, the evolution of sociality and vocal learning. Here, we uncovered vocal recognition of individual affiliative calls in a social bird from the most basal avian group studied so far. • We studied acoustic variation in affiliative distance calls in wild greylag geese. • Geese were able to recognize distance calls from different individuals. • Fitness-related traits were correlated with vocal responses. [ABSTRACT FROM AUTHOR]

Many species rely on individual recognition (i.e., the use of individual signals to identify and remember a conspecific) to tune their social interactions. However, little is known about how the configuration of the sensory system may affect the perception of individual recognition signals over space. Utilizing a visual modeling approach, we quantified (1) the threshold distance between the receiver and the signaler at which individual recognition can no longer accurately occur, and (2) the regions of the head most likely to contain the individual recognition signals. We used chickens (Gallus gallus) as our study species, as they use visual individual recognition and additionally have a well-studied visual system. We took pictures of different individuals and followed a visual modeling approach considering color vision, visual acuity, and pattern processing of the receiver. We found that distance degrades the quality of information in potential individual recognition signals. We estimated that the neighbor distance at which a receiver may have difficulty recognizing a conspecific was between 0.25 and 0.30 m in chickens, which may be related to a decrease in available features of the potential signal. This signal perception threshold closely matches the recognition distance predicted by previous behavioral approaches. Additionally, we found that certain regions of the head (beak, cheek, comb, eye) may be good candidates for individual recognition signals. Overall, our findings support that recognition in chickens occurs at short distances due to constraints imposed by their visual system, which can affect the costs and benefits associated with social spacing in groups. [ABSTRACT FROM AUTHOR]

Longevity of odour memories, particularly those acquired during early development, has been documented in a wide range of taxa. Here, we report that kittens of the domestic cat retained a memory into adult life of their mother´s body odour experienced before weaning. Kittens from 15 litters were tested when permanently separated from their mother at weaning on postnatal week 8, and tested again when 4 and 6 months and over 1 year of age. When presented with a simultaneous three-way choice between body odour of their own mother, of an unknown female of similar reproductive condition and a blank stimulus, weaning-age kittens sniffed the cotton swab with the odour of an unknown female longer. This preference, however, changed when as adults the subjects sniffed the cotton swab with their own mother's odour longer. We conclude that kittens form a long-lasting memory of the body odour of their mother, and by implication, that mothers retain an individual odour signature sufficiently stable across age and changes in their reproductive state to be distinguishable by their adult offspring. What this means in functional or cognitive terms is not yet clear. Does such "recognition" have a specific biological function and a specific cognitive representation? Or is it rather part of a more general phenomenon well known in (human) olfaction of odours that are familiar generally being judged more pleasant, and that might then influence olfactory-guided behaviour in a variety of contexts? [ABSTRACT FROM AUTHOR]

Abstract Population studies often incorporate capture‐mark‐recapture (CMR) techniques to gather information on long‐term biological and demographic characteristics. A fundamental requirement for CMR studies is that an individual must be uniquely and permanently marked to ensure reliable reidentification throughout its lifespan. Photographic identification involving automated photographic identification software has become a popular and efficient noninvasive method for identifying individuals based on natural markings. However, few studies have (a) robustly assessed the performance of automated programs by using a double‐marking system or (b) determined their efficacy for long‐term studies by incorporating multi‐year data. Here, we evaluated the performance of the program Interactive Individual Identification System (I3S) by cross‐validating photographic identifications based on the head scale pattern of the prairie lizard (Sceloporus consobrinus) with individual microsatellite genotyping (N = 863). Further, we assessed the efficacy of the program to identify individuals over time by comparing error rates between within‐year and between‐year recaptures. Recaptured lizards were correctly identified by I3S in 94.1% of cases. We estimated a false rejection rate (FRR) of 5.9% and a false acceptance rate (FAR) of 0%. By using I3S, we correctly identified 97.8% of within‐year recaptures (FRR = 2.2%; FAR = 0%) and 91.1% of between‐year recaptures (FRR = 8.9%; FAR = 0%). Misidentifications were primarily due to poor photograph quality (N = 4). However, two misidentifications were caused by indistinct scale configuration due to scale damage (N = 1) and ontogenetic changes in head scalation between capture events (N = 1). We conclude that automated photographic identification based on head scale patterns is a reliable and accurate method for identifying individuals over time. Because many lizard or reptilian species possess variable head squamation, this method has potential for successful application in many species.

Abstract Background Human-animal interactions with mutual benefits in the wild are rare. Such positive interactions seem to require an intricate knowledge from the human side on the animals’ behavior and their habitat. In southern Brazil, dolphins and human net-casting fishers have specialized in a cooperative foraging, in which fishers report being able to identify and name dolphins. Here, we evaluate the consensus in their ability to recognize the individual dolphins they interact with. By investigating the reliability of this recognition process, we assess the pros and cons of relying on the fishers’ traditional knowledge to further understand the behavior and ecology of dolphins at the individual level. We also assess the potential role of traditional knowledge for the maintenance of this unusual interaction. Methods We interviewed 38 fishers using a semi-structured questionnaire. During each interview, we evaluate their recognition ability of dolphins by showing high-quality photos of dorsal fins of different dolphins, asking questions about the dolphins’ behavior and traits, and about how fishers recognize each dolphin. We also evaluated information about the fishers. Different indices were used to measure the fishers’ ability to recognize dolphins via photos, and their consensus on individual identification. These indices were modeled as functions of traits of both dolphins and fishers to investigate which ones influence the recognition process. Results We found that fishers can primarily recognize dolphins by natural marks in the dorsal fin but there was little consensus in recognition. Fishers also tend to repeat the name of the most “popular” dolphins for different photos, indicating low reliability in individual recognition. We also found that fishers who learned from relatives (vertical learning) how to interact with dolphins tend to be more accurate and have higher consensus in dolphin recognition than those fishers who learned from friends (horizontal learning) or individually. Conclusion Artisanal fishers have a deep understanding of the dolphins and the system they are inserted in. However, the lack of consensus in identifying individual dolphins herein reported indicates that using their traditional knowledge to further understand dolphin behavior and ecology at the individual level requires caution. Our study also suggests that the transmission of this tradition from parents to sons can be crucial to preserve such a unique human-animal positive interaction in its original form.

Wild animals encounter humans on a regular basis, but humans vary widely in their behaviour: whereas many people ignore wild animals, some people present a threat, while others encourage animals' presence through feeding. Humans thus send mixed messages to which animals must respond appropriately to be successful. Some species appear to circumvent this problem by discriminating among and/or socially learning about humans, but it is not clear whether such learning strategies are actually beneficial in most cases. Using an individual-based model, we consider how learning rate, individual recognition (IR) of humans, and social learning (SL) affect wild animals' ability to reach an optimal avoidance strategy when foraging in areas frequented by humans. We show that ‘true’ IR of humans could be costly. We also find that a fast learning rate, while useful when human populations are homogeneous or highly dangerous, can cause unwarranted avoidance in other scenarios if animals generalize. SL reduces this problem by allowing conspecifics to observe benign interactions with humans. SL and a fast learning rate also improve the viability of IR. These results provide an insight into how wild animals may be affected by, and how they may cope with, contrasting human behaviour.

Swimming crab Portunus trituberculatus is a vital crab species in coastal areas of China. In this study, an individual re-identification method based on Pyramidal Feature Fusion Model (PFFM) for P. trituberculatus was proposed. This method took the carapace texture of P. trituberculatus as a “biological fingerprint” and extracted carapace texture features, including global features and local features, to identify P. trituberculatus. Furthermore, this method utilized a weight adaptive module to improve re-identification (ReID) accuracy for the P. trituberculatus individuals with the incomplete carapace. To strengthen the discrimination of the extracted features, triplet loss was adopted in the model training process to improve the effectiveness of P. trituberculatus ReID. Furthermore, three experiments, i.e., PFFM on the effect of pyramidal model, P. trituberculatus features analysis, and comparisons to the State-of-the-Arts, were carried out to evaluate PFFM performance. The results showed that the mean average precision (mAP) and Rank-1 values of the proposed method reached 93.2 and 93% in the left half occlusion case, and mAP and Rank-1 values reached 71.8 and 75.4% in the upper half occlusion case. By using the experiments, the effectiveness and robustness of the proposed method were verified.

By analyzing the voiceprint characteristics of giant panda’s voice, this study proposes a giant panda individual recognition method based on the characteristics of the composite Mel composite frequency cepstral coefficient (CMFCC) and proves that the characteristic sequence of the CMFCC has long-range dependent characteristics. First, the MFCC (Mel composite frequency cepstral coefficient) with a low frequency resolution is obtained by the Mel filter bank; then, the inverse Mel frequency cepstral coefficient (IMFCC) features of giant panda calls are extracted. The CMFCC characteristic sequence of giant panda voice composed of the MFCC and IMFCC improves the resolution of high- and low-frequency resolution characteristics of giant panda voice. Finally, the first-order difference characteristic parameters of the MFCC are integrated to obtain the difference characteristics between frames. Through experiments, the improvement of the system recognition effect is verified, and the recognition accuracy meets the theoretical expectation.

Visual recognition of three-dimensional signals, such as faces, is challenging because the signals appear different from different viewpoints. A flexible but cognitively challenging solution is viewpoint-independent recognition, where receivers identify signals from novel viewing angles. Here, we used same/different concept learning to test viewpoint-independent face recognition in Polistes fuscatus, a wasp that uses facial patterns to individually identify conspecifics. We found that wasps use extrapolation to identify novel views of conspecific faces. For example, wasps identify a pair of pictures of the same wasp as the 'same', even if the pictures are taken from different views (e.g. one face 0 deg rotation, one face 60 deg rotation). This result is notable because it provides the first evidence of view-invariant recognition via extrapolation in an invertebrate. The results suggest that viewpoint-independent recognition via extrapolation may be a widespread strategy to facilitate individual face recognition., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Recognizing conspecifics is vitally important for differentiating kin, mates, offspring and social threats. 1 Although often reliant upon chemical or visual cues, individual recognition across the animal kingdom is also facilitated by unique acoustic signatures in vocalizations. 2-4 However, amongst the large Muroidea superfamily of rodents that encompasses laboratory species amenable to neurobiological studies, there is scant behavioral evidence for individual vocal recognition despite individual acoustic variation. 5-10 Playback studies have found evidence for coarse communicative functions like mate attraction and territorial defense, but limited finer ability to discriminate known individuals' vocalizations. 11-17 Such a capacity would be adaptive for species that form lifelong pair bonds requiring partner identification across timescales, distances and sensory modalities, so to improve the chance of finding individual vocal recognition in a Muroid rodent, we investigated vocal communication in the prairie vole ( Microtus ochrogaster ) - one of the few socially monogamous mammals. 18 We found that the ultrasonic vocalizations of adult prairie voles can communicate individual identity. Even though the vocalizations of individual males change after cohabitating with a female to form a bond, acoustic variation across individuals is greater than within an individual so that vocalizations of different males in a common context are identifiable above chance. Critically, females behaviorally discriminate their partner's vocalizations over a stranger's, even if emitted to another stimulus female. These results establish the acoustic and behavioral foundation for individual vocal recognition in prairie voles, where neurobiological tools 19-22 enable future studies revealing its causal neural mechanisms., Competing Interests: DECLARATION OF INTERESTS The authors declare no competing interests.

Rodents are known to signal using odors to communicate information including their sex, age, reproductive state, and unique identity. Conspecifics can recognize these signals and behaviorally respond in sex‐specific ways. However, we know little about how males and females might differ in their responses to signals from individuals or how the sexes might differ in their ability to recognize their own identity. Such signals of identity are important because they can modulate the behavior of receivers, and allow for responses related to aggression, territory maintenance, affiliation, and reproduction. To assess how males and females might differ in their responses to individual familiar and novel social signals, and their own individual signals compared to novel same‐sex conspecifics, we tested southern giant pouched rats (Cricetomys ansorgei) using a habituation–discrimination paradigm. Only females showed individual recognition and discriminated among males, preferring novel males. Females also discriminated between their own scent and a novel conspecific odor. Males did not discriminate or demonstrate individual recognition. Male and female differences in response to opposite‐sex odors demonstrated that males do not discriminate between familiar and novel reproductively available females, but females discriminate and prefer to investigate novel males. [ABSTRACT FROM AUTHOR]

The ability to recognize mates, kin, offspring and neighbors by their individually distinctive traits—individual recognition (IR)—is widespread in animals. Much work has investigated IR from the perspective of the recognizer, but less is known about the extent to which signals have evolved to facilitate IR. To explore this, one approach is to compare putative identity signals among species that differ in life history and extent of IR. In Common Murres (Uria aalge), a colonially breeding seabird, the eggs of individual females are remarkably variable in terms of color and pattern (maculation). Common Murres also appear to recognize their own eggs, leading to the hypothesis that variable egg phenotypes evolved to promote recognizability. However, we lack a quantitative assessment of the egg pattern information in Common Murres and their close relatives. Here, we analyzed images of eggs laid by four alcid species: Common Murres, Thick‐billed Murres (Uria lomvia), Razorbills (Alca torda) and Dovekies (Alle alle). We extracted pattern measures believed to be relevant to bird vision and calculated Beecher's information statistic (Hs), which allowed us to compare the amount of identity information contained in each species' egg patterns. Murres, which nest in dense colonies and can recognize their own eggs, have egg patterns with a relatively large amount of identity information compared to Razorbills and Dovekies. Egg recognition has not been demonstrated in Razorbills and Dovekies, whose colonies are less dense. Our results are consistent with the hypothesis that complex patterns of Murre eggs may have evolved to increase individual recognizability. Research Highlights: Egg patterns in Common and Thick‐billed Murres may have evolved for recognizability in crowded breeding colonies.We quantified egg patterns and found that Murre egg patterns contain more identity information than those of Razorbills and Dovekies. [ABSTRACT FROM AUTHOR]