Biota colombiana

26-35

Authors: Edgar Cifuentes, Juliana Vélez Gómez, Simon J. Butler

Ecoacoustic approaches have the potential to provide rapid biodiversity assessments and avoid costly fieldwork. Their use in biodiversity studies for improving management and conservation of natural landscapes has grown considerably in recent years. Standardised methods for sampling acoustic information that deliver reliable and consistent results within and between ecosystems are still lacking. Sampling frequency and duration are particularly important considerations because shorter, intermittent recordings mean recorder batteries last longer and data processing is less computationally intensive, but a smaller proportion of the available soundscape is sampled. Here, we compare acoustic indices and processing time for subsamples of increasing duration clipped from 94 one-hour recordings, to test how different acoustic indices behave, in order to identify the minimum sample length required. Our results suggest that short recordings distributed across the survey period accurately represent acoustic patterns, while optimizing data collection and processing. ACI and H are the most stable indices, showing an ideal sampling schedule of ten 1-minute samples in an hour. Although ADI, AEI and NDSI well represent acoustic patterns under the same sampling schedule, these are more robust under continuous recording formats. Such targeted subsampling could greatly reduce data storage and computational power requirements in large-scale and long-term projects.

57-73

Authors: Mónica Isabel Retamosa Izaguirre, David Segura Sequeira, Jimmy Barrantes-Madrigal, Manuel Spínola Parallada, Óscar Ramírez-Alán

We assessed the structural complexity of vegetation, birds and soundscapes in two areas of Braulio Carrillo National Park, Costa Rica, with different road exposure, as baseline information for conservation and management. We measured vegetation structure complexity, surveyed birds and recorded soundscapes in an area adjacent to the National Highway 32 (Quebrada) and another area 20 km away (Ceibo). Quebrada presented a more open forest structure and lower density of trees and shrubs; lower evenness and higher acoustic complexity, higher bioacoustic activity and sound pressure level; higher bird abundance and richness. Ceibo showed a higher density of trees and shrubs, higher complexity of vegetation structure, higher proportion of biophonies than anthrophonies, and an acoustic community with higher diversity and entropy. The study sites differed in characteristics of their bird communities in an unexpected way; these differences appear to be mostly influenced by the structure and complexity of the vegetation surrounding the road. However, the soundscapes seemed to properly reflect the habitat condition, and are promising for evaluating the ecological condition of a site.

96-107

Authors: Sara Gonçalves Santos, Nadia Pieretti, Robert John Young, Marina Duarte

Anthropogenic noise, which is part of an urban soundscape, can negatively affect the behaviour of wild animals. Here we investigated how biophony (animal sounds) was affected by noise in an urban Brazilian forest fragment. Our hypothesis was that noise and biophony would differ between the border and the centre of the forest fragment (i.e., lower biophony predicted in noisy areas). Two passive acoustic monitoring devices were used to record soundscapes one week per month, 24 hour per day, from May to July 2012. The Acoustic Complexity Index (ACI) was used to quantify biophony and the Power Spectral Density (PSD) to quantify urban noise. PSD and ACI were higher on the border than in the centre of the fragment. PSD was lower in July, while the ACI did not significantly vary between months. Noise levels were also higher on the border. Conversely, potential species richness was higher in the centre of the forest fragment. Higher biophony at noisy sites can be interpreted as behavioural responses of species for communicating in noisy areas. Alternatively, they could be the result of species segregation by degree of vocal plasticity or due to differences in composition of communities.

122-132

Authors: Julián A. Rojas-Morales, Enrique La Marca, Héctor E. Ramírez-Chaves

We describe the advertisement call of seven males and observations on the natural history related to the parental attention by males, of a population of nurse frogs attributed to the Leucostethus fraterdanieli complex from the Central Cordillera in the Department of Caldas, Colombia. The advertisement call consists of a long sequence of repeated (x̅ = 143 notes.min-1) pulsed notes, which have an average duration of 79 ± 17 ms (range 63-122 ms), separated by time intervals between 187-413 ms (289 ± 67 ms). The dominant frequency values are in the range between 3209-3520 Hz. Our results suggest differences in temporal and spectral parameters between the population studied and other populations assigned to L. fraterdanieli, L. brachistriatus, and the recently described L. jota.

149-163

Authors: Laura Andrea Hoyos Cardona, Juan Ulloa, Juan Luis Parra Vergara

Acoustic monitoring allows the evaluation of spatio-temporal changes in animal populations. However, analyzing large volumes of information is challenging. We evaluate the performance of a detection technique (autodetec function of the R warbleR package) to identify vocalizations of Megascops centralis, using 6877 one-minute recordings from 21 sites in the vicinity of the Jaguas dam, Andes of Antioquia Colombia., All vocalizations were manually annotated and two sites (597 recordings) with the highest number of records (49 and 34) were selected to evaluate the algorithm. The function was implemented with audios at two sampling rates (44 100 Hz and 22 050 Hz) and three amplitude thresholds (5, 10, and 20). We assessed the performance of this function in terms of its sensitivity and specificity, and we estimate the probability of detection of a signal according to its quality. Sensitivity and specificity showed great variation (0-0.48 and 0.5-0.98 respectively) and the probability of detection of a signal increased with its quality (poor: 0.12, medium: 0.27 andhigh: 0.64). Acoustic monitoring has an enormous potential, and its success depends, in part, on the availability of automatic recognition tools, that are open access and can be easily implemented. This development can be achieved by strengthening acoustic collections.

184-199

Authors: Milena Paulo-Moreno, Pedro Sanchez-Palomino

We observed a population of cotton-top tamarins (Saguinus oedipus, Primates: Callitrichidae) in the municipality of Santa Catalina, Bolívar, northern Colombia. We observed them over 100 hours, and we recorded 16 hours of vocalizations, which were subsequently digitalized at 44.1 kHz, using Protools. We analyzed 2617 sounds with Raven 1.2, with the aim of identifying the phonetic units forming the vocal repertoire of this species, according to the following acoustic parameters: Duration (ms), change frequency (Hz), peak frequency (Hz), start frequency (Hz) and harmonics. In order to describe the vocal repertoire, the phonemes were classified into 11 groups, according to their form. The acoustic parameters were analyzed using confidence intervals, and 49 different sounds were identified. By assembling the phonetic units, 14 different vocalizations wer identified. The sounds emitted by cotton-top tamarins are of short duration (= 0.0215 s). The lowest start frequency registered is 322.7 Hz and the highest is 13 956.5 Hz. The change in frequency ranges from 113.8 to 13 652.2 Hz. The peak frequencies range from 0 to 10 077.6 Hz. On the other hand, 37.4 % of sound lacks harmonics, and the remainder 62.6 % show between 1 and 12 harmonics.