Vocal communication is important for social interactions in sheep, yet knowledge about lamb vocal behaviour during early development remains limited. This study aimed to examine vocalisation changes, breed differences and vocal individuality in bleats of lambs during the post-weaning period. High-pitched vocalisations of lambs (n = 18) from three dairy sheep breeds were recorded at three developmental time points (112, 154 and 196 days old). Twenty-four acoustic parameters were extracted and entered into a principal component analysis, followed by linear mixed models to evaluate the effects of breed, age and body size on acoustic characteristics. Discriminant function analysis were further applied to examine vocal individuality. Breed influenced components related to energy distribution and formant frequencies, while age affected maximum formant frequencies, fundamental frequency and call duration. The examined breeds showed similar developmental patterns in the acoustic parameters. Discriminant analysis revealed modest individual classification. Individuality was also maintained across the examined time points. Vocal characteristics also showed meaningful variation between breeds, indicating that breed-specific acoustic patterns can be distinguished alongside individual signatures. The results demonstrate that lamb vocalisations are shaped by both developmental and breed-related factors while maintaining lasting individual acoustic signatures.
Understanding acoustic divergence is essential for delimiting species, as advertisement calls often function as primary signals for mate recognition and reproductive isolation in anurans. However, for many Neotropical frogs such data remain scarce. Here, we investigate acoustic, morphological and ecological divergence between Charadrahyla nephila and the recently described C. viruela occurring along an elevational gradient in the cloud forests of Oaxaca, Mexico. We recorded 106 advertisement calls from 21 males at two localities corresponding to C. nephila and C. viruela. Most acoustic variables showed significant differences between species. Individuals from C. nephila were smaller and lighter than individuals from C. viruela. C. nephila individuals also occupied thinner perches and occurred in cooler, drier environments consistent with elevational variation in microhabitats. The congruence across acoustic, morphological and ecological differences supports the hypothesis of two independent evolutionary lineages corroborating the existence of C. nephila and C. viruela species. These results highlight the taxonomic and conservation significance of acoustic divergence, as recognising distinct lineages may necessitate reassessment of the species' IUCN Red List status due to narrower distribution ranges.
Underwater noise is widely recognised as an emerging pollutant with negative impacts on the marine environment, including marine fauna. However, accurately measuring and evaluating its effects on animals remains a challenge, especially in the field. To address this, laboratory playback experiments offer a valuable and controlled approach to study these effects in a range of species. In this work, we present experimental setups designed to assess behavioural and physiological responses of invertebrates, with a focus on deuterostome species, to anthropogenic noise. The approach integrates (i) systems that accommodate species of varying sizes and life habits, (ii) a playback signal equalisation protocol and (iii) characterisation of sound pressure levels and particle motion associated with the playback stimulus. Homogeneous playback equipment was used to ensure consistency in all trials. These experimental setups are intended to support the development of future studies to better understand the effects of anthropogenic noise on marine life.
The genus Pristimantis, with over 637 species, is the most diverse vertebrate lineage in the Neotropics. Despite this diversity, advertisement calls - acoustic signals essential for species delimitation, conservation monitoring, and reproductive ecology - remain poorly documented. We present the first comprehensive assessment of advertisement call knowledge in Pristimantis through a systematic review of peer-reviewed literature (1983-2026). We identified 115 studies describing calls for 160 of 637 species (25.27%). We additionally developed a 12-variable quality index revealing a marked positive trend in reporting standards from 2014 onwards. Our analysis reveals strong geographic, taxonomic, and conservation biases. Megadiverse countries harbouring over 80% of species (Colombia, Ecuador, Per & uacute;), show low documentation rates (12-22%) and threatened species are consistently underrepresented (15-20%). Coverage among species groups varies widely (0-66%), reflecting differences in vocal behaviour and detectability. Notably, only 25.0% of species with described calls have complete documentation, including voucher specimen, deposited audio recording, and type locality description, underscoring persistent gaps in traceability and reproducibility. These deficiencies limit passive acoustic monitoring, automated species recognition, and evidence-based conservation. Our findings provide a quantitative baseline to prioritise research, guide fieldwork in undersampled regions, and promote collaborative efforts to address critical knowledge gaps in this hyperdiverse genus.
