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Table of Content
    Volume 31 Issue 1
    20 January 2023
    There are more and more bioacoustic researches conducted in China as a result of advancement in passive acoustic monitoring technology. This issue reviews the progress in bioacoustics monitoring and research of wild vertebrates. The upper part of the background is the waveform of acoustic signal, the lower part of the background is the animal's habitats; the center shows the acoustic monitoring device, surrounded by groups that rely on acoustic communication. (Design: Zhishu Xiao)
    Original Papers: Animal Diversity
    Progress in bioacoustics monitoring and research of wild vertebrates in China
    Jianguo Cui, Zhishu Xiao
    Biodiv Sci. 2023, 31 (1):  23023.  doi:10.17520/biods.2023023
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    Interdisciplinary development trends of contemporary bioacoustics and the opportunities for China
    Zhishu Xiao, Jianguo Cui, Daiping Wang, Zhitao Wang, Jinhong Luo, Jie Xie
    Biodiv Sci. 2023, 31 (1):  22423.  doi:10.17520/biods.2022423
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    Background: Contemporary bioacoustics is an interdisciplinary science by combining biology and ecology with acoustics. Through the mutual penetration and integration of technological innovation and many disciplinary fields from natural and social science, it has gradually formed the characteristics of transdisciplinary fields, such as strong compatibility, high technological dependence, and wide application scenarios. Though bioacoustics has expanded into many interdisciplinary fields and application scenarios, a comprehensive understanding of bioacoustics as a discipline in scientific communities at home and abroad are still lacking. Therefore, it is necessary to systematically evaluate the development status, main research issues and frontier topics of contemporary bioacoustics.

    Scope of bioacoustics: Contemporary bioacoustics is a new interdisciplinary science that studies the relationship between sounds of organisms and their ecological environment. With the technological innovation and application of interdisciplinary fields such as digital recording, electronics and microelectronics, artificial intelligence and information science, the research depth and breadth of contemporary bioacoustics are continually expanding, and it has gradually formed a diversified frontier issues with biology, ecology and other disciplines. Currently, bioacoustics is mainly guided by theories and methods from basic disciplines of biology and ecology. The research focus is to reveal the interaction and scientific theories of various sounds among organisms, and among organisms, human beings and the environment in the natural and man-made environment, so as to provide theoretical basis and solutions for human beings to recognize, protect and utilize bioacoustic resources.

    Aims: By reviewing relevant literature at home and abroad, combined with our practice and thinking, this paper focuses on the interdisciplinary properties and key topics of contemporary bioacoustics, and introduces frontier topics and development trends in animal bioacoustics, ecological acoustics, underwater bioacoustics, environmental bioacoustics, conservation bioacoustics, computational bioacoustics, and bioacoustic monitoring and analysis. The status and development opportunities of bioacoustics research in China are also evaluated and analyzed, and the future discipline construction is prospected.

    Conclusions: Bioacoustic research is conducive to the fully understanding and scientific use of bioacoustic resources and related scientific theories. Its achievements can be used as scientific guidance and decision-making basis for life health and biosafety, the conservation and utilization of bioacoustic resources and the protection of ecological environment. In sum, interdisciplinary development of bioacoustics can provide high-quality services for the progress of ecological civilization and the construction of a beautiful and healthy China.

    Application, progress, and future perspective of passive acoustic monitoring in terrestrial mammal research
    Haigang Ma, Penglai Fan
    Biodiv Sci. 2023, 31 (1):  22374.  doi:10.17520/biods.2022374
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    Background & Aims: Passive acoustic monitoring (PAM) is an observational method that collects acoustic signals of wildlife and the surrounding environment using automatic sound recorders. PAM itself is a multidisciplinary technique, integrating biology, ecology, acoustics, and computer science, and was developed in the 1990s first to study bats and primates. Since then, PAM has been utilized in a variety of research contexts to study animal behavior, ecology, and conservation biology. However, a systematic review of the progress of the field is lacking.

    Progress: Here, we review how PAM has been used to monitor terrestrial mammal activity patterns, habitat use, species distribution, population size and density, biodiversity, and human influence. We also identify factors which prevent its wider application, such as the complexity of storing and managing acoustic data, limitations of acoustic indices, challenges associated with automated identification of species or individuals, and the overall cost of equipment. As a consequence, we observe limited use of PAM in terrestrial mammal research, especially in China.

    Perspective: Finally, we discuss potential novel applications of PAM to study terrestrial mammals. We highlight the importance of establishing and improving standardized PAM networks and data management platforms, developing citizen science programs, encouraging participation of more scientific institutions, and expanding the presence of acoustic monitors particularly throughout protected areas. PAM is an indispensable technique which can further support efforts to conserve biodiversity and increase ecological consciousness in China.

    Spatiotemporal characteristics and influencing factors of animal soundscape in urban green spaces
    Yuhua Cen, Peng Wang, Qingchun Chen, Chengyun Zhang, Shang Yu, Ke Hu, Yang Liu, Rongbo Xiao
    Biodiv Sci. 2023, 31 (1):  22359.  doi:10.17520/biods.2022359
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    Background & Aims: The animal community is a key element constituting the urban green-space ecosystem. As an important ecological component of wild animal communities, the soundscape is of great significance in guiding urban green-space landscape design and biodiversity conservation measures. This paper examined 67 articles from the core collection of Web of Science published between 2005 and 2022 to comprehensively analyze the spatiotemporal patterns of and influences on animal soundscapes in urban green spaces.

    Findings: The animal soundscape of urban green space was influenced by environmental-spatial gradients and vegetation spatial structure. Animal sound diversity was inversely correlated with altitude, latitude, urbanization degree, and was also related to vegetation type and height. Phenology of the urban soundscape also showed diurnal, seasonal, and annual variation, including characteristics such as dawn and dusk avian choruses, insect and amphibians nocturnal choruses, and other aspects of animals’ seasonal and annual vocalization patterns. The factors that affect the urban animal soundscape thus include mainly vegetation, environment, anthropogenic interference, and self-driving of animals.

    Prospects: Despite being one of the hotspots of current soundscape ecology research, animal soundscape research faces challenges such as insufficient investigation of large spatiotemporal scales. Promising directions for future research include the quantitative analysis of influential factors and their response mechanisms as well as the establishment of a global animal soundscape database.

    Application and prospect of network analysis in the studies of animal vocal communication and bioacoustics
    Ke Deng, Jianguo Cui
    Biodiv Sci. 2023, 31 (1):  22318.  doi:10.17520/biods.2022318
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    Background & Aim: Animal social network analysis (ASNA) is a toolbox used to examine animal sociality, quantify various social relationships between individuals, and uncover links between individual behavior and dynamics of social structures, which is widely used in studies of animal behavior across a variety of taxa. In addition, a series of measurements in ASNA are very suitable for investigating vocal interactions and song structure. Here we reviewed the applications of ASNA in studies of animal vocal communication and bioacoustics.

    Progress: Firstly, we introduced a description of basic concepts and some measurements. Secondly, we described the use of ASNA to construct vocal networks and quantify vocal interactions based on field and laboratory studies, and the application prospect of ASNA combined with passive acoustic monitoring technology. Thirdly, we discussed the advantages of ASNA in analyzing song similarity and geographic variation. Finally, we summarized the application of ASNA in the analysis of song structure and syntactical rules.

    Conclusion: ASNA provides a comprehensive perspective and new ideas for studying animal communication networks and investigating the adaptive evolution of acoustic signals.

    Diel and seasonal variability of the forest soundscape in the Northeast China Tiger and Leopard National Park
    Yifei Sun, Shizheng Wang, Jiawei Feng, Tianming Wang
    Biodiv Sci. 2023, 31 (1):  22523.  doi:10.17520/biods.2022523
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    Aims: Passive acoustic monitoring (PAM) and acoustic indices could provide an effective method for monitoring changes in forest soundscapes. However, annual dynamics of soundscapes remain poorly understood. We studied the diel, seasonal patterns, and shifts of the biotic component of the acoustic environment in the Northeast China Tiger and Leopard National Park.

    Methods: We sampled recordings at 52 sites from June 2020 to June 2021 within the park. For each recording, we calculated the acoustic complexity index (ACI), acoustic diversity index (ADI), acoustic evenness index (AEI), bioacoustic index (BIO), normalized difference soundscape index (NDSI), acoustic entropy (H), and power spectral density (PSD) of each 1 kHz frequency bin within the 1-21 kHz frequency band. We divided a diel cycle into 4 phases (dawn, day, dusk, and night) according to the times the sun rose and set, and utilized generalized additive models (GAMs) to fit the curves of the diel and annual patterns of acoustic indices.

    Results: The soundscapes demonstrated a marked distinction among all four phases, especially between night and other time periods. The soundscapes typically had more acoustic complexity, diversity, and biophony intensity during the daytime. However, night soundscapes showed more acoustic complexity throughout the summer season. In spring, the acoustic diversity index and bioacoustic index were higher at dawn due to intensive bird choruses. Acoustic complexity, diversity, and intensity of biophony demonstrate varied annual dynamics and peaked from May to October.

    Conclusion: This study identified measurements that effectively summarize baseline soundscape attributes and prioritizes future opportunities for integrating non-acoustic and acoustic variables in research in order to inform area-specific management questions within the Northeast China Tiger and Leopard National Park.

    Effects of bird migration on the temporal patterns of the wetland soundscape in the downstream region of the Tumen River Basin of China
    Shizheng Wang, Yifei Sun, Zhenzhen Li, Yue Shu, Jiawei Feng, Tianming Wang
    Biodiv Sci. 2023, 31 (1):  22337.  doi:10.17520/biods.2022337
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    Aims: Bioacoustics may provide an effective method for monitoring changes in wetland bird activity and soundscape, yet phenological and seasonal patterns remain poorly understood. In this study, we examine the seasonal and diel soundscapes, as well as the utility of bioacoustics in detecting changes in songbird phenology in the downstream region of the Tumen River Basin of China.

    Methods: Between November 2020 and December 2021, 91,988 acoustic recordings were collected at 10 sites from the Jingxin Wetland, a stopover ground for numerous migratory bird species. For each sample, we record the acoustic complexity index (ACI), bioacoustic index (BIO), acoustic evenness index (AEI), normalized difference soundscape index (NDSI) and power spectral density (PSD) values.

    Results: Our analysis show that seasonal shifts and bird migration have a significant effect on the composition and diversity of wetland soundscape. The 1-2 kHz daytime vocal signals of wild geese dominated the soundscapes of two migration periods (February-April and October-November), resulting in a significant decrease in NDSI and a significant increase in PSD at 1-2 kHz. Acoustic indices are sensitive to bird migration, but changes in bioacoustics were less abrupt in the fall, suggesting that spring recordings are better suited to indicate phenology. Summer birds and insects dominated the soundscape of non-migration period.

    Conclusion: We find that the soundscape of the Tumen River’s downstream wetland exhibits clear annual and diurnal rhythm. Our experiment demonstrates the use of multiple acoustic indices in conjunction can effectively monitor changes in migratory bird phenology, particularly the time and population size at which wild geese fly back north in the spring. Furthermore, we conclude that acoustic recordings, in combination with acoustic indices, may be a useful method for tracking shifts in songbird communities caused by climate change.

    Diversity of anurans in the Bawangling Area of Hainan National Park based on auto-recording technique
    Yanjun Jin, Longhui Zhao, Yuanyu Qin, Jichao Wang
    Biodiv Sci. 2023, 31 (1):  22360.  doi:10.17520/biods.2022360
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    Aims: The Bawangling Area of the National Park of Hainan Tropical Rainforest belongs to biodiversity hotspot area of China, and its natural environment is ideal for amphibians. However, the diversity of anuran amphibians in the area is still unknown. Here we investigated the diversity of anurans in the region and explored the relationships between anuran calling and the environment.

    Methods: The emerging bio-acoustic methods were applied in this study. Five areas with different habitats were selected in the Bawangling Area of the National Park. In each area, three recorders were deployed to consistently collect sound data in June, August to September, December 2021 and January to March 2022, respectively (over 15 days in each period).

    Results: In total, we recorded 17 frog species belonging to 11 genera and 6 families. Four seasons had different species composition among which the least species appeared in winter (December). Species composition also varied in different areas among which Feilie had most species. Of these 17 species, 12 species called only at night, while 3 species called mainly at night and occasionally during the day, and 2 species called actively throughout the day. Moreover, rainfall had different effects on species in different habitats. Rainfall did not affect the calling activity of Amolops torrentis and Hylarana guentheri inhabiting permanent water, as well as Microhyla fissipes inhabiting diverse environemnts. The calling activity of Limnonectes fragilisdwelling in shallow streams and Leptobrachium hainanense living on the ground was higher on raining days.

    Conclusions: In sum, season, day and night, location and rainfall may affect the diversity and calling activity of frogs in Bawangling region. This study not only enriches the ecological data of amphibians in Hainan tropical rainforest, but also contributes to the ecological conservation and assessment of wildlife in the Bawangling Area of the Hainan Tropical Rainforest National Park.

    Changes in vocal characteristics of male concave-eared torrent frogs (Odorrana tormota) in different chorus tides
    Hao Dong, Ziyi Ke, Yatao Wu, Junqi Miao, Fang Zhang
    Biodiv Sci. 2023, 31 (1):  22217.  doi:10.17520/biods.2022217
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    Aims: Sound communication plays a crucial role in the reproductive process of concave-eared torrent frogs (Odorrana tormota). The vocalization strategies adopted by the male O. tormota under sexual selection pressures have particular research significance. For example, it can help us to better comprehend the effect of sexual selective pressure on amphibian calls. However, there is still a lack of research on the adaptation strategies of male O. tormota under different chorus periods.

    Methods: Based on the field experiments, we labeled male O. tormota (n = 12) from March 2021 to May 2021. We used Wilcoxon signed-rank test to examine the difference between the total content of nonlinear vocal phenomena (NLP) and its components (chaos content, subharmonics content, frequency jump), and both the duration of the call and calling rate of male O. tormota (n = 12) during the high and low tide of the chorus.

    Results: There were no significant differences in some NLP components (such as chaos content and subharmonics content) and the duration of the call of male frogs between the high and low tide of the chorus. However, the total content of NLP and some NLP components (such as frequency jump) in the low tide period of the chorus were significantly higher than those in the high tide period of the chorus. Similarly, the calling rate during the chorus in high tide was significantly higher than those in the low tide.

    Conclusion: The calling strategies of male O. tormota in different chorus periods are not alike. During the low tide period, when there is less sexual selection pressure, male O. tormota are better able to attract females by increasing the NLP content in their calls, expanding the distance of sound transmission, and increasing the unpredictability of sound. During the high tide period, when there is more sexual selection pressure, male frogs make individual calls more prominent by increasing the calling rate, thereby improving the success rate of amplexus.

    Giant panda mothers can discriminate own neonates from others based on their squalls
    Lin Zhao, Jianbin Cheng, Wen Zeng, Guo Li, Haibing Gong, Guiquan Zhang, Dingzhen Liu
    Biodiv Sci. 2023, 31 (1):  22362.  doi:10.17520/biods.2022362
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    Background & Aim: In many group-living mammal species, mothers can recognize calls from their own offspring, but little research has been done in solitary species. The giant panda (Ailuropoda melanoleuca) is a solitary species, yet there is high competition for breeding dens and an overlap in giant panda territory. Competition between pregnant giant panda females for denning becomes strained in the wild because the availability of old tree caves has decreased in recent years. Giant panda neonates are highly altricial, weighing little more than 0.1% of the adult weight, and rely on constant maternal care for growth and survival. To elicit maternal care, 045-day old neonates use vocalizations to express distress and their physiological needs. Here, we use the giant panda as a model to investigate if mothers can discriminate calls of their own cubs from those of other cubs.

    Methods: In this study, we first investigated if neonate squalls have the potential of encoding an individual-specific acoustic signature, and then examined whether mothers can discriminate squalls of their own from all other neonates by playing the audio recordings of their squalls to the mothers.

    Results: Analyzing results based on 274 call samples from six cubs revealed that 14 out of 17 analyzed acoustic parameters of squalls have the potential for individual identity coding (PIC > 1), indicating a potential of an individual acoustic signature. Further discriminant analysis revealed that 78.5% of the squalls were correctly paired to the calling individual. The playback experiments demonstrated that mothers responded to squalls of their own neonates significantly more frequently than to squalls of other neonates (P = 0.008), indicating that mothers can identify their own offspring from their squalls.

    Conclusions: The squall calls of newborn pandas likely encode an individual acoustic signature, and panda mothers can distinguish the acoustic structure of squalls of their own neonates from that of other cubs. The results of this study provide valuable insights for the ex-situ conservation and breeding management of giant pandas in captivity and are conducive to improving the survival rate of giant panda cubs in captivity.

    Syllable clustering analysis-based passive acoustic monitoring technology and its application in bird monitoring
    Keyi Wu, Wenda Ruan, Difeng Zhou, Qingchen Chen, Chengyun Zhang, Xinyuan Pan, Shang Yu, Yang Liu, Rongbo Xiao
    Biodiv Sci. 2023, 31 (1):  22370.  doi:10.17520/biods.2022370
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    Aims: Passive acoustic monitoring has proven to be an effective method for monitoring bird biodiversity, as it allows for the analysis of important information such as bird songs and calls. The complexity and variations of bird songs and calls make it difficult to quickly and accurately identify bird species using voiceprint analysis. Solving this problem is essential for the successful implementation of a voiceprint-based bird diversity monitoring scheme.

    Methods: This paper proposes a syllable clustering analysis-based approach for bird song/call monitoring framework. The first step is to extract syllables from voiceprint data using audio features such as pitch and frequency flatness. These syllables are then trained using a combination of unsupervised representation learning and a Dirichlet process hybrid model. The final steps are clustering the syllables and inferring their categories.

    Results: (1) The analysis results show that, the proposed framework can achieve nearly 90% clustering accuracy when handling the published recordings of Lonchura striata song repository; (2) On the basis, the paper conducts unsupervised syllable clustering analysis on ten species of birds monitored in Baiyun Mountain Forest Park, Guangzhou, between April and May 2022. It verifies that the proposed framework can not only support bird species identification, but also meet the rapid species identification application requirements. This can be extended further to obtain the statistics and changes in time, frequency and quantity of various bird songs/calls.

    Conclusion: The analysis results of this paper show us that, the syllable clustering-based bird song/call monitoring framework can significantly reduce the requirements for manually annotated training data. This also overcomes the shortcomings of the traditional framework in dealing with overlapping bird songs. Therefore, it provides a comprehensive solution for applications such as rapid species recognition, syllable sequence analysis, and population abundance analysis in bird diversity monitoring.

    Deep learning techniques for bird chirp recognition task
    Zhuofan Xie, Dingzhao Li, Haixin Sun, Anmin Zhang
    Biodiv Sci. 2023, 31 (1):  22308.  doi:10.17520/biods.2022308
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    Background: In the ecosystem, birds are an important component, which is crucial for regulating the ecological environment and monitoring biodiversity, and can even assist in predicting natural disasters such as earthquakes and tsunamis by monitoring the movement of birds and listening to their abnormal calls, so bird sound recognition and abnormal call detection have become popular research directions. However, low recognition rate is caused to the problems of insufficient feature extraction in traditional bird sound recognition methods.

    Method: In this paper, we used a fusion feature method combined with deep learning to extract bird sound features. The fusion features were obtained by splicing the original signal parameters with the modified log-Meier spectral difference parameters; the deep learning method was based on the DenseNet121 network structure and incorporated the self-attention module and the central loss function for bird sound recognition. The self-attentive module partially improved the feature representation of key channels; the central loss function was used to solve the problem of incompact intra-class features. We used the data of 10 bird sounds from the Xeno-Canto World Wild Bird Sounds public dataset to test the accuracy of bird chirp recognition.

    Conclusion In this paper, a neural network structure containing self-attention mechanism and center loss function is proposed for bird song recognition. Its verification accuracy reaches to 96.9%. The code is open source to Github: CarrieX6/-Xeno-Canto-.git.

    A meta-analysis of the effects in alpha acoustic indices
    Yanyi Wang, Yimei Zhang, Canwei Xia, Anders Pape Møller
    Biodiv Sci. 2023, 31 (1):  22369.  doi:10.17520/biods.2022369
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    Background: Many animals such as mammals, birds, amphibians, fishes and arthropods, produce sounds when moving, communicating or sensing their environment. Building upon the rich legacies of bioacoustics and animal communication, the acoustic properties from soundscape are used to monitor and assess the changes in animal communities and related environments. During the past decade, many acoustic indices have been developed and can be divided into two categories, namely alpha acoustic indices and beta acoustic indices. Alpha acoustic indices reflect the information in the recording while beta acoustic indices focus on comparison of differences between different recordings. There are far more empirical studies of the application of alpha acoustic indices than beta acoustic indices. However, patterns in alpha acoustic indices have been contradictory. Before alpha indices can be applied widely, it is necessary to understand better how well they reflect the communities and the environments to be monitored.

    Aims: To make general inferences from the mixed evidence, associations between alpha acoustic indices and animal diversity, habitat quality, animal activity were quantitatively reviewed based on the meta-analytic approach.

    Methods: Both key word searches and cross-reference searches were conducted, and 2,845 pairs of data related to alpha acoustic indices and other variables were collected from 136 references. For the alpha acoustic indices which were used more than 50 times, the direction of their associations was tested by sign test. Then, the maximum likelihood method was employed to estimate the probability density function of the summary effect (i.e., the correlation coefficient between the alpha acoustic index and other variable). Lastly, the correlation coefficients were calculated based on the probability density function.

    Results & Conclusion: Eight commonly used alpha acoustic indices were involved in the study, namely acoustic complexity index (ACI), acoustic entropy index (H) (including two closely related indices: temporal entropy and spectral entropy index), bioacoustic index (BI), normalized difference soundscape index (NDSI), acoustic diversity index (ADI), acoustic evenness index (AEI), acoustic richness index (AR), and number of peaks (NP). Among these acoustic indices, ACI was the most frequently used and positively related with animal diversity, habitat quality, and animal activity. The highest association coefficient appeared at the relationship between ACI and terrestrial animal activity, with the mean effect size 0.53. Besides, the correlation coefficients in other acoustic indices were always trivial, with the effect sizes generally less than 0.30. The only significantly negative relationship occurred between AEI and terrestrial habitat quality, with the mean effect size ‒0.18. The robustness of the main results was thoroughly analyzed, and the strengths and weaknesses of acoustic monitoring through acoustic indices were also discussed. This study is expected to provide a guideline for the selection of alpha acoustic indices in future research.

    Characteristics and applications of beta acoustic indices
    Yimei Zhang, Yanyi Wang, Yan He, Bing Zhou, Miao Tian, Canwei Xia
    Biodiv Sci. 2023, 31 (1):  22513.  doi:10.17520/biods.2022513
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    Background & Aims: In recent years, with recording equipment becoming more accessible to researchers through improved performance and reduced prices, habitat and biodiversity assessment conducted through audio recording has developed rapidly. An acoustic index is the quantification of the overall characteristics of sound, which is influenced by both the habitat characteristics and the composition and abundance of species in the study area. Therefore, there is a correlation, at least in theory, amongst acoustic indices, habitat, and biodiversity. An acoustic index can be divided into two categories: reflecting the information within the recordings and comparing the differences between different recordings, which are named an alpha acoustic index and beta acoustic index, respectively. With the increase of utilizing recording monitoring equipment in studies, the demand for comparing acoustic indices at different times and places has also increased. Therefore, the development and application of the beta acoustic index is an important direction of acoustic index research. Here, we introduced some commonly used beta acoustic indices, and explored the mathematical properties (non-negativity, self-identity, symmetry, triangle inequality, finiteness) of these indices. We also summarized applications of these beta acoustic indices by conducting a systematic literature review.

    Results & Discussion: In this paper, we introduced 11 commonly utilized beta acoustic indices: mutual information index (MI), relative frequency dissimilarity index (RF), temporal dissimilarity index (TD), spectral dissimilarity index (SD), acoustic dissimilarity index (AD), Kolmogorov-Smirnov distance index (KS), Kullback-Leibler distance index (KL), cumulative spectral dissimilarity index (CS), correlation-based dissimilarity index (CB), Itakura-Saito distance index (IS), and log-spectral distance index (LS). Three of these indices (RF, KS, CS) satisfy all the properties (non-negativity, self-identity, symmetry, triangle inequality, finiteness), and another three indices (TD, SD, LS) satisfy the metric properties (non-negativity, self-identity, symmetry, triangle inequality). Cross-reference searches were conducted in the Web of Science database (, accessed on 2022-10-20), and 14 articles were found concerning the application of beta acoustic indices. Amongst these articles, SD was used most frequently in seven articles; AD and CS were used in five and four articles, respectively, while other beta acoustic indices were used no more than three times. The application of beta acoustic indices mainly focused on three aspects: the changes in time rhythm, habitat characteristics, or biological composition.

    Prospect: We pointed out three areas in need of urgent development in the study/application of beta acoustic indices: designing new indices, optimizing the algorithm for existing indices, and strengthening empirical research.

    Exploring the application of acoustic indices in the assessment of bird diversity in urban forests
    Qi Bian, Cheng Wang, He Cheng, Dan Han, Yilin Zhao, Luqin Yin
    Biodiv Sci. 2023, 31 (1):  22080.  doi:10.17520/biods.2022080
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    Aims: Calling is an important way for birds to communicate and transmit information to each other. This provides a unique opportunity to assess bird diversity through acoustic monitoring. The use of acoustic indices for the rapid assessment of biodiversity is an emerging survey method, but the complex sonic environment in urban forests may lead to bias. The feasibility of using acoustic indices to assess bird diversity in urban forests still needs to be further explored.

    Methods: To understand the effectiveness of acoustic indices in urban forests, we set up 50 matrix survey sample sites in Beijing Eastern Suburb Forest Park. Bird sample point observations and simultaneous acoustic data collection were conducted monthly from April to June 2021. In order to verify the effectiveness of acoustic monitoring, we compared the results of the two methods. Spearman correlation analysis and generalized linear mixed models were used to assess the relationship between six commonly used acoustic indices and bird richness and abundance. The performance of each acoustic index was subsequently measured.

    Results: (1) A total of 35 species, comprising 10 orders and 23 families, were recorded in this experiment. Although the total number of species identified through acoustic monitoring was equal to bird observations, there were discrepancies between which specific bird species were observed. (2) The correlation between acoustic indices and bird richness and abundance varied significantly in different months. The acoustic complexity index (ACI) and normalized difference sound index (NDSI) outperformed others were key variables for assessing bird diversity. (3) Acoustic indices had higher predictive power for bird abundance (R2m = 0.32, R2c = 0.80) than richness (R2m = 0.12, R2c = 0.18).

    Conclusion: Acoustic monitoring provides a promising tool for urban biodiversity assessment, but there are still many areas that need to be explored. With the gradual improvement of methods and technology, acoustic monitoring has great potential in the tracking and conservation management of urban biodiversity.

    A dataset on the call characteristics of 43 anuran species in China
    Ke Deng, Xiaoping Wang, Bicheng Zhu Longhui Zhao, Yue Yang, Yanlin Cai, Xiaoqian Sun, Tongliang Wang, Jianguo Cui
    Biodiv Sci. 2023, 31 (1):  22344.  doi:10.17520/biods.2022344
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    Calls of anuran species (frogs and toads) are generally species-specific. This means that bioacoustics can be used to investigate species diversity and monitor species, but only if the call characteristics are known. In this study, we summarize the call data and sample information of 43 anuran species (from 26 genera in 7 families) recorded in the field with high-fidelity recorders from 2012 to 2020. In addition, we provide a call characteristic dataset with oscillograms and spectrograms of 61 calls (after noise reduction processing). The dataset contains temporal and spectral characteristics of the calls, such as the note number, note duration, inter-note interval, call duration, dominant frequency, fundamental frequency, harmonics, and whether they are monosyllabic or multisyllabic. This dataset is essential for using acoustic techniques to survey species diversity and monitor anuran species in China using their calls.

    Distribution and niche overlap of American mink and Eurasian otter in Northeast China
    Minhao Chen, Chao Zhang, Jiadong Wang, Zhenjie Zhan, Junzhi Chen, Xiaofeng Luan
    Biodiv Sci. 2023, 31 (1):  22289.  doi:10.17520/biods.2022289
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    Aims: As an invasive species, the American mink (Neovison vison) has caused a series of ecological problems in Europe. It competes for ecological space with the Eurasian otter (Lutra lutra), and its invasiveness poses a serious threat to local biodiversity and ecosystem. However, minks have been introduced into the Northeast China for more than 70 years, yet there are few studies on the field population of minks in China. The purpose of this study is to understand the influencing factors and invasive range distribution of the mink population and the competition relationship between minks and otters with a similar ecological niche.

    Methods: In this study, based on the distribution information obtained from field investigation and literature, the potential distribution areas of American mink and Eurasian otter were identified by utilizing an ensemble model, and the geospatial invasion risk of American mink to Eurasian otter was assessed. Principal component analysis (PCA) was used to assess niche overlap and influencing factors.

    Results: The potential distribution area of American mink was 61,944.57 km2, while the potential distribution area of Eurasian otter was 83,590.94 km2, and the overlapping area was 50,544.21 km2, accounting for 60.47% of the potential distribution area of otters in Northeast China. With distribution by province, otters in Heilongjiang Province had the highest risk of invasion by minks, and the overlap ratio of potential distribution area is 78.94%, followed by Jilin province with an overlap of 53.80%. The environmental niche of minks and otters was highly overlapped, with Schoener’s D value reaching 0.60. The results of single-factor niche analysis indicated that otters were more sensitive to cultivated land density than minks and concentrate in low cultivated land density areas. Otters and minks tended to choose areas with higher forest density, but minks had a smoother selection of forest density and were less dependent on forest than otters. Minks preferred areas with lower precipitation than otters and otters preferred higher-altitude habitats to minks.

    Conclusion: According to the geographical distribution characteristics and the results of niche analysis, we suggest that the competition between otter and mink should be regulated by controlling human disturbance to suppress the mink invasion in Northeast China.

    Patterns and environmental drivers of the butterfly diversity in the western region of Qinling Mountains
    Chao Zhang, Juan Li, Haiyun Cheng, Jiachong Duan, Zhao Pan
    Biodiv Sci. 2023, 31 (1):  22272.  doi:10.17520/biods.2022272
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    Aims: The present work aims to analyze the environmental drivers of diversity in the butterfly community in the western Qinling Mountains.

    Methods: In the autumn of 2020 and spring and summer of 2021, we investigated butterfly diversity in the western region of Qinling Mountains using line transects across multiple habitat types in 15 sampling areas. We used trend and extrapolation analyses for estimating α diversity, and non-metric multidimensional scaling (NMDS) and cluster analyses for β diversity. For determining drivers of butterfly diversity, we fit environmental factors to diversity indices using a generalized additive model (GAM).

    Results: We observed a total of 8,898 individuals representing 169 species, 84 genera, and 5 families. Of these families, the highest number of individuals were from Pieridae (N = 3,671), and the most number of species were from Nymphalidae (N = 80). We found that α diversity was highest during the summer and in coniferous and broad-leaved forests. For β diversity, we found the highest degree of similarity between coniferous and broad-leaved forest and deciduous broad-leaved forest, the low similarity between seasons, and that species are concentrated in spring and summer but relatively dispersed in autumn. The GAM fitted curves demonstrated several key relationships between environmental factors and butterfly diversity, including: (1) plant heterogeneity was correlated with butterfly community diversity; (2) an ambient temperature between 24℃ and 30℃ underlined a higher Pielou evenness index and a more stable butterfly community structure; and (3) humidity between 70% and 85% was associated with a higher Simpson index.

    Conclusion: Butterfly community composition and diversity in the western region of Qinling Mountains were closely related to habitat type and have a distinct chronological relationship with seasons. Plant cover, abundance, humidity, and temperature are important factors in maintaining the diversity of butterfly species on a regional scale.

    Spawning ground microhabitat selection by the Chinhai spiny newt (Echinotriton chinhaiensis)
    Tingting Li, Xihong Zhu, Guangnian Wu, Xiao Song, Aichun Xu
    Biodiv Sci. 2023, 31 (1):  22293.  doi:10.17520/biods.2022293
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    Aim: The Chinhai spiny newt (Echinotriton chinhaiensis) has received a first-class National Protected Wildlife status in China. Its population is under severe threats such as habitat degradation and habitat loss. Spawning is crucial for the population growth of E. chinhaiensis. Therefore, understanding the preference of spawning sites can be crucial for protection and integrated management of the Chinhai spiny newt and its spawning ground. In this paper, we carried the study to identify the main environmental variables that affected the selection of spawning ground microhabitat of E. chinhaiensis, and to provide baseline data for spawning ground protection, transformation and reconstruction.

    Methods: From March to May 2021, we investigated 18 microhabitat variables of spawning sites (n = 105) and non-spawning sites (n = 70) of E. chinhaiensis at the Forest Farm of Beilun District, Ningbo City, Zhejiang Province during its breeding period. Goodness of fit test was utilized to analyze the differences between 3 disordered categorical variables, and the habitat preference index was used to analyze the habitat selection. To examine patterns in microhabitat selection of E. chinhaiensis, we used Binary Logistic Regression Model to analyze 15 numerical variables.

    Results: The results indicated that, generally, E. chinhaiensis preferred to spawn on steep terrain with soil tilting towards the puddles (18.64° ± 1.18°), deeper leaf litter (5.19 ± 0.18 cm), less soil water content (33.51% ± 1.87%). In addition, eggs of E. chinhaiensis were often spawned near small rocks or trees (54.27 ± 3.84 cm in a distance), which provided shelter (2,994.63 ± 316.17 cm3 in volume). Leaf litter depth and volume of large shelter (rocks or trees) were both the most important in determining the spawning microhabitat of E. chinhaiensis, secondary importance was distance to nearest large shelter.

    Conclusions: E. chinhaiensis selected microhabitat for spawning that simultaneously meet the requirements of shelter characteristics (leaf litter depth, large shelter tape, volume of large shelter, distance from large shelter), water feature (spawning site aspect, slope), microclimate (soil water content, substrate type). Variables related to shelter are important characteristics for choosing the microhabitat by E. chinhaiensis. For effective species conservation, we recommend protection of deciduous broad-leaved forest around spawning ground.

    Technology and Methodology
    Generating pseudo-absence samples of invasive species based on the similarity of geographical environment in the Yangtze River Economic Belt
    Weifeng Xiao, Lüxing Zuo, Wentao Yang, Chaokui Li
    Biodiv Sci. 2023, 31 (1):  22094.  doi:10.17520/biods.2022094
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    Aims: Obtaining diversity samples of invasive alien species is crucial for species spatial distribution models. This includes both invasive species presence and absence samples. However, most invasive species data sets lack explicit spatial information for absent species samples. Consequently, generating effective pseudo-absence samples of invasive species is a significant issue for constructing species spatial distribution models. This paper proposed an invasive species pseudo-absence sampling method based on the similarities of geographical environments.

    Methods: First, the principal component analysis (PCA) was used to model the linear correlation of the original variables. Then the K-means algorithm was used to cluster the invasive species samples and calculate the geographic environment similarity of each of them based on the PCA components. Second, the pseudo-absence samples of invasive species were generated by establishing a framework for similarity measurement of PCA components and confidence level calculation of pseudo-absence samples. Finally, based on random sampling, one-class support vector machine (OCSVM) and the proposed approach, the logistic regression and support vector machine (SVM) were adopted to implement the accuracy evaluation by using the dataset regarding the invasive species Erigeron annuus in the Yangtze River Economic Belt.

    Results Compared with random sampling and OCSVM, the proposed sampling approach had better prediction results from logistic regression and SVM, and the feasibility and effectiveness of the proposed approach were validated.

    ConclusionsThe strategy for generating pseudo-absence samples based on the similarity of geographical environments solves the problem of erroneously sampling potential invasive species presence owing to random sampling, meanwhile, the confidence level of species absence samples can be used to obtain different levels of adaptive areas of invasive species.

    The “principle of plan as a whole” for the national botanical gardens’ constructive system
    Zaifu Xu
    Biodiv Sci. 2023, 31 (1):  22470.  doi:10.17520/biods.2022470
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    Background: This is a new strategy of the “principle of plan as a whole” for the national botanical gardens’ constructive system in integrating plant conservation (both in situ and ex situ) for carrying out the Convention on Biological Diversity (CBD).

    Aims & Conclusion: The Chinese national botanical gardens need an arrangement for coordinating the population size of the living plant cultivation for different functional plants, especially for endangered species, which is needed to protect more eco-types and populations. In China, other botanical gardens (BGs) carry out ex situ conservation for endangered plants as well. Moreover, some Chinese BGs have almost synchronizing to carry out ex situ conservation for endangered plants with the top BGs in the world. It is recognized that their achievements for ex situ conservation has had both their own strong points, and the problems also exist more or less as to the efficiency of ex situconservation. So that the point of view, the work of the Chinese national BGs should follow the standards of ex situconservation by the world top BGs is open to question.

    Suggestions on standardizing the zoological and the botanical nomenclatures of the Himalayas area in the Chinese language
    Qi Zhang
    Biodiv Sci. 2023, 31 (1):  22131.  doi:10.17520/biods.2022131
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    Background & Aim: Although the International Union of Biological Sciences (IUBS) has clarified the legal status of “scientific name”, the use of Chinese name is still inseparable in practical work. This article analyzes the Chinese names of 6 genera and 402 species which are named after the Latinization of “himalaya” and the Chinese names of 1 genus and 37 species which are named refer to “Himalaya”. This paper aims to standardize the Chinese nomenclature of species involving the Himalayas.

    Methods: This paper summarizes the basic principles and methods of naming species in the Chinese language by referring to laws and regulations, regional historical geography and related history of animal and plant species naming.

    Conclusion & Suggestions: This research leads to three principles: (1) The standard geographical names of species should not be simplified arbitrarily. (2) “Himalaya” has a specific meaning and should not be used in simplified forms of species’ Chinese names. The Chinese name should use complete geographical names. (3) Correcting obscure Chinese species names will neither change the position of the species in the scientific classification system nor do harm to the system itself. Based on these principles, we suggest to revise the incorrect Chinese names of 3 genera and 35 species.

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