Search

Bioacoustic monitoring and classification of animal communication signals has developed into a powerful tool for measuring and monitoring species diversity within complex communities and habitats. The high number of stridulating species among Orthoptera allows their detection and classification in a non-invasive and economic way, particularly in habitats where visual observations are difficult or even impossible, such as tropical rainforests. Major sound archives were queried for Orthoptera songs, with special emphasis on usability as reference training libraries for computer algorithms. Orthoptera songs are highly stereotyped, reliable taxonomic features. However, exploitation of songs for acoustic profiling is limited by the small number of reference recordings: existing song libraries represent only about 1000 species, mainly from Europe and North America, covering less than 10% of extant stridulating Orthoptera species. Available databases are fragmented and lack tools for song annotation and efficient feature-based searching. Results from recent bioacoustic surveys illustrate the potential of the method, but also the challenges and bottlenecks impeding further progress. A major problem is time-consuming data analysis of recordings. Computer-aided identification software exists for classification and identification of cricket and grasshopper songs, but these tools are still far from practical for field application. A framework for acoustic profiling of Orthoptera should consist of the following components: (1) Protocols for standardized acoustic sampling, at species and community levels, using acoustic data loggers for autonomous long-term recordings; (2) Open access to and efficient management of song data and voucher specimens, involving the Orthoptera Species File (OSF) and Global Biodiversity Information Facility (GBIF); (3) An infrastructure for automatized analysis and song classification; and (4) Complementation and improvement of Orthoptera sound libraries using OSF as the taxonomic backbone and repository for representative song recordings. Taxonomists should be encouraged, or even obliged, to deposit original recordings, particularly if they form part of species descriptions or revisions. [ABSTRACT FROM AUTHOR]

Efficient acoustic communication in multispecies assemblages is challenging due to the presence of heterospecific signals. Masking interference and signal confusion of similarly structured signals can impose fitness costs and, thus, drive evolutionary processes that shape acoustic signals to reduce their overlap in signal space. Although the partitioning of signal space has been frequently studied in frog and bird communities, this topic has received much less attention with reference to insects that communicate acoustically. In this study, we examined the role of acoustic competition in a tropical cricket community and tested the following hypotheses: 1) cosignaling species are expected to exhibit more dissimilar calling songs as compared with species that are spatially and/or temporally separated and 2) species signaling with similar song frequencies, who are thereby subject to energetic masking, are more likely to differ in the temporal domain of their calling songs. Using non-metric multidimensional scaling and pairwise comparison methods to measure acoustic dissimilarity, we found no evidence for either hypothesis: the acoustic signals of species pairs that cosignaled or used similar calling frequencies did not significantly differ from those of species that were spatially/temporally segregated or had large song frequency differences. In conclusion, for the acoustically communicating cricket community investigated, no supportive evidence for the partitioning hypothesis and the widespread belief that acoustic competition has led to divergent selection pressures on signal structure to avoid masking interference was found. Instead, we argue that selection pressures on sensory/neuronal mechanisms seem to more strongly drive reliable communication. [ABSTRACT FROM AUTHOR]

Acoustic emissions of animals serve communicative purposes and most often contain species-specific and individual information exploitable to listeners, rendering bioacoustics a valuable tool for biodiversity monitoring. Recording bioacoustic signals allows reproducible species identification. There is a great need for increased use and further development of automated animal sound recording and identification to improve monitoring efficiency and accuracy for the benefit of conservation. Greece, with its high number of endemic species, represents a hotspot for European Biodiversity, including Orthopteran insects. Songs of many Orthoptera might be employed for the inventorying and monitoring of individual species and communities. We assessed the regional spatio-temporal composition of Orthoptera species at the Hymettos near Athens, which is a Natura 2000 site under constant threat due to the surrounding megacity. Within the framework of the EU Life Plus funded AmiBio project, we documented the Orthopteran species' habitat characteristics, their co-occurrence and phenology. We found, in total, 20 species with seven to ten Orthoptera at locations characterised by diverse vegetation patterns of perennial herbs and bushes. For the purposes of implementation of an automated remote monitoring scheme, we identified sampling sites with high Orthopteran diversity, allowing the monitoring of all singing Orthoptera within single localities. By analysing sound depositories and adding recordings from new sample individuals, we established a song library as prerequisites for future automatic song detection. Based on our results, acoustic recording units have been placed at remote sites at the Hymettos. We discuss recommendations for further studies to fully employ the potential of automated acoustic monitoring of Orthoptera. A reliable assessment of singing Orthoptera needs recording units covering ultrasound. Due to high attenuation and absorbance by the vegetation, particularly of the high frequencies characterising Orthopteran songs, positioning of microphones at sites is critical: the microphone sensor network has to be an order of magnitude denser than for monitoring birds. [ABSTRACT FROM AUTHOR]

In species-rich biomes such as tropical rainforests, the efficiency of intraspecific acoustic communication will strongly depend on the degree of signal overlap. Signal interference deteriorates detection, recognition, and localization of conspecific signals. Thus, the communication space should be partitioned sufficiently to reduce masking interference and to promote intraspecific communication. Here, we studied the community organization of a tropical cricket assemblage with respect to its multidimensional niche axes, such as song frequencies, space (horizontal and vertical), and time, affecting acoustic communication. We used the null model approach to test whether observed community patterns differed from those expected by chance. The assemblage clearly showed partitioning in the spectral domain of calling frequencies of their songs. Furthermore, the range of song frequencies occupied by species is positively correlated with the distance to the average calling frequency of its adjacent neighbors. Thus, species tended to use a greater range of frequency channels for intraspecific communication if the frequency space is available. Our results support the idea that competition for the acoustic communication channel may have resulted in niche segregation along the frequency axes. Concerning the spatiotemporal organization at the community level the spatial (horizontal) distribution appeared to be randomly structured, whereas we found a significant vertical stratification between species. At a temporal scale, the assemblage aggregated their calling activity with an observed niche overlap significantly greater than expected by chance. However, combining the spatial and temporal distribution resulted in low co-occurrence of pairwise species association, consequently reducing chances for masking events. [ABSTRACT FROM PUBLISHER]

Because of call frequency overlap and masking interference, the airborne sound channel represents a limited resource for communication in a species-rich cricket community like the tropical rainforest. Here we studied the frequency tuning of an auditory neuron mediating phonotaxis in the rainforest cricket Paroecanthus podagrosus, suffering from strong competition, in comparison with the same homologous neuron in two species of European field crickets, where such competition does not exist. As predicted, the rainforest species exhibited a more selective tuning compared with the European counterparts. The filter reduced background nocturnal noise levels by 26dB, compared with only 16 and 10dB in the two European species. We also quantified the performance of the sensory filter under the different filter regimes by examining the representation of the species-specific amplitude modulation of the male calling song, when embedded in background noise. Again, the filter of the rainforest cricket performed significantly better in terms of representing this important signal parameter. The neuronal representation of the calling song pattern within receivers was maintained for a wide range of signal-to-noise ratios because of the more sharply tuned sensory system and selective attention mechanisms. Finally, the rainforest cricket also showed an almost perfect match between the filter for sensitivity and the peripheral filter for directional hearing, in contrast to its European counterparts. We discuss the consequences of these adaptations for intraspecific acoustic communication and reproductive isolation between species. [ABSTRACT FROM AUTHOR]

Analyses of satellite telemetry data of White Storks Ciconia ciconia from the eastern populations at their stopover sites and staging areas document the importance of the Luangwa Valley, eastern Zambia, as a migration corridor bridging eastern and southern Africa. Twice each year from November to April, up to 100 000 White Storks may transit and rest in the area. Radio-tracked storks took from one to four days in either direction to traverse the entire Luangwa Valley. The preferred habitats for stopover sites and short-term staging, obtained using GIS, are deciduous woodlands and scrublands with sparse trees; croplands are preferred for longer staging periods. [ABSTRACT FROM AUTHOR]

The present paper reviews the state of knowledge of migratory species protected under the Bonn Convention (Convention on the Conservation of Migratory Species of Wild Animals) and presents first results from the “Global Register of Migratory Species” (GROMS). GROMS summarises our knowledge on migratory species within one relational database in combination with a geographical information system (GIS). GROMS will reveal information deficiencies, support the Convention on the Conservation of Migratory Species of Wild Animals, and contribute to the Clearinghouse Mechanism under the Convention on Biological Diversity. At present, GROMS contains 412 species distribution maps in GIS format. As an initial example of the potential of GIS‐analysis, GIS‐maps of birds and mammals were intersected with administrative borders, and the number of species was calculated for each province. The resulting map shows a high diversity in temperate regions, which is in contrast to maps that usually show most “biodiversity hotspots” to be in the tropics. Consequences for conservation policies are discussed and future prospects for GIS analysis are outlined. [ABSTRACT FROM PUBLISHER]

Songs of Orthoptera can be used for inventorying and monitoring of individual species and communities. Acoustic parameters such as carrier frequency and pulse rates allow the definition of recognizable taxonomic units (RTUs) which help to overcome the taxonomic impediment due to our scanty knowledge, particularly of tropical faunas. Bioacoustic diversity is a first estimate for species richness and provides baseline data which can be a prerequisite for conservation. Additional ecological and behavioural information such as habitat preference andsinging schedules can be inferred. Many Orthoptera are sensitive indicator species for habitat quality in temperate and tropical ecosystems. Examples are given for evaluation of habitat quality and deterioration by acoustic detection of Orthoptera. [ABSTRACT FROM AUTHOR]