How to count bird calls? Vocal activity indices may provide different insights into bird abundance and behaviour depending on species traits

Passive acoustic monitoring (PAM) has become an important tool for surveying birds, and there is a growing demand for approaches to obtain abundance and behavioural information from PAM recordings. Changes in bird populations have been assessed by counting recorded calls and calculating the vocal activity rate (VAR, i.e. the number of calls per recording time). However, bird calls could be counted in various ways and depending on species traits, these call counts could give us different insights on bird abundance, vocal behaviour and/or habitat use. Our study had two goals: (1) to present and evaluate two new indices based on call counts, the detection rate (DR, i.e. the number of 1-min recordings in which the presence of a target vocalization is detected) and the maximum count per minute (MAX, i.e. the maximum number of calls found in a 1-min recording); and (2) to present a conceptual framework showing how the interpretations of VAR, DR and MAX could depend on the index and on species traits. For three Neotropical bird species with distinct traits, we calculated VAR, DR and MAX based on PAM data from 25 sites in the Yucatan Peninsula (Mexico) that varied in their degree of anthropogenic habitat disturbance. We found moderate to high correlations between the indices and higher temporal variability in VAR compared to DR and MAX. We also found different effect sizes of habitat disturbance on the three species and indices. We suggest that DR might be a more reliable index of relative abundance than VAR for species whose calling behaviour exhibits a high cue rate and that MAX may be suitable for estimating family or flock size in gregarious birds. Our findings show the potential usefulness of developing new indices based on call counts to generate ecological hypotheses and assess changes in bird abundance and behaviour

Utilising Drone Technology in Primatology for 3D Mapping

Emergent Unmanned Aerial System (or drone) technology allows the 3-dimensional mapping of forest landscapes, allowing a new perspective of arboreal primate habitat use. Utilising UASs in primatological studies enables the assessment of habitat quality for different arboreal primate species, the identification of discreet forms of anthropogenic disturbance (such as historical selective logging), and detailed investigation of canopy use by arboreal primate species. Combining 3D canopy structure with microclimate measurements, we can see how canopy structure buffers solar radiation and how arboreal species may be affected by future climate change. We present data on a study of the arboreal primate community in a lowland section of the Gunung Leuser Ecosystem in northern Sumatra, focusing on how 3D canopy structure effects ranging (siamang, Symphalangus syndactylus), different primate species’ population densities (lar gibbon, Hylobates lar, siamang and Thomas langur, Presbytis thomasi) and habitat selection (orang-utan, Pongo abelii and siamang) and how UAS technology can be utilised in other future studies; the potential opportunities, challenges and pitfalls

Reduced geographic variation in roars in different habitats rejects the acoustic adaptation hypothesis in the black-and-gold howler monkey (Alouatta caraya)

Vocalizations used for long‐range communication must disperse without significant structural changes to be decoded by receivers. The acoustic adaptation hypothesis (AAH) holds that, since acoustic signals are influenced by the habitat in which they disperse, sounds will possess specific structural characteristics to diminish sound degradation. Additionally, vocalizations can also be influenced by genetics, anatomy, and/or cultural aspects. Here, we tested the AAH through quantitative comparisons of roars in four allopatric populations of the black‐and‐gold howler monkey (Alouatta caraya) across an environmental gradient from open to closed, in northeastern Argentina. At each site, we obtained good‐quality recordings from three adult males, also between July and November 2013, conducted vegetation surveys (measuring tree density, canopy closure, and vertical structure), evaluated potential masking of roars by gathering environmental sound samples, and assessed sound attenuation of a synthetic tone at three different distances: 10 m (landmark reference distance), 50, and 100 m. We also tested the alternative hypothesis that acoustic properties of roars could be explained by population genetic divergence. Our results did not support the AAH. Although our four study sites were significantly different in vegetation structure, conforming to an open‐to‐closed gradient, roars of A. caraya were not different among populations. Likewise, although environmental sound differed between sites, we found no evidence of environmental sound affecting the acoustic properties of roars. The attenuation of the synthetic tone was only near significant at 100 m distance between both extreme sites from the environmental gradient. The four A. caraya study populations grouped into three genetically differentiated clusters. Since roar features were independent from population genetic clustering, we reject the genetic hypothesis too. The combination of high amplitude and low peak frequency of roars, coupled to small home range size and extensive overlap between neighboring groups, allows roars to keep their communication value across habitats without need of specific environmental tuning.Fil: Holzmann, Ingrid. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del Noroeste Argentino. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto de Bio y Geociencias del Noroeste Argentino; ArgentinaFil: Areta, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del Noroeste Argentino. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto de Bio y Geociencias del Noroeste Argentino; Argentin

Age and social affinity effects on contact call interactions in free-ranging spider monkeys

International audienceNonhuman primates’ vocal repertoire has shown little plasticity, with immatures producing adult-like acoustic structures. Yet, the use of different call types shows a degree of socially dependent flexibility during development. In several nonhuman primate species, group members exchange contact calls respecting a set of social and temporal rules that may be learned (e.g., overlap avoidance, turn-taking, social selection of interacting partners, and call type matching). Here, we study the use of contact calls in free-living adult and immature (old and young) spider monkeys (Ateles geoffroyi). We focused our study in two contact call types of the species’ repertoire: whinnies and high-whinnies. Our results suggest that individuals in all age classes produced both call types, with immatures producing less frequently the whinny call type. Immature individuals exchanged calls less often than adults, although their contribution increased with age. Conversely, mature individuals regulated their emissions by (1) exchanging more calls with their preferred affiliative partner and (2) matching the call type, while immatures did not. Our results show that contact call usage changes during development and suggest that adult rules might be learned. We argue that call matching is a “conversational rule” that young individuals acquire with apparent call-type-dependent variations during development. Our findings support the idea that social factors influence vocal development in nonhuman primates

Spider Monkeys (Ateles geoffroyi) habituate to anthropogenic pressure in a low-impact tourism area: Insights from a multi-method approach

Shared habitats between humans and other animals are increasing in the twenty- first century, which may require behavioral flexibility from animal species to adjust to these new environments. We evaluated the effects of anthropogenic pressure on Geoffroy’s spider monkeys (Ateles geoffroyi) in a low-impact tourism area. Over the course of 18 months, we repeatedly assessed the presence of spider monkeys at 49 sampling locations for a total of 98 hours of point-count sampling and 6,768 hours of passive acoustic monitoring. Combining these data, we assessed the effects of human settlements, recreational areas, forest loss, and anthropogenic noise on spi- der monkey abundance using Royle–Nichols models. We found positive associations of various sources of anthropogenic pressure with spider monkey abundance. We interpret the results as Geoffroy´s spider monkeys habituating to various sources of anthropogenic pressure, and conclude that the species has the potential to live in low-impacted habitats shared with humans, but that conservation efforts should focus on evaluating the risk of human–wildlife conflict emergence. By combining our multi-method survey with Royle–Nichols statistical models, we offer a flex- ible approach to monitor primate populations with a high degree of fission–fusion dynamics, while controlling for heterogeneity in detection probability

Dominance style is a key predictor of vocal use and evolution across nonhuman primates

Animal communication has long been thought to be subject to pressures and constraints associated with social relationships. However, our understanding of how the nature and quality of social relationships relates to the use and evolution of communication is limited by a lack of directly comparable methods across multiple levels of analysis. Here, we analysed observational data from 111 wild groups belonging to 26 non-human primate species, to test how vocal communication relates to dominance style (the strictness with which a dominance hierarchy is enforced, ranging from 'despotic' to 'tolerant'). At the individual-level, we found that dominant individuals who were more tolerant vocalized at a higher rate than their despotic counterparts. This indicates that tolerance within a relationship may place pressure on the dominant partner to communicate more during social interactions. At the species-level, however, despotic species exhibited a larger repertoire of hierarchy-related vocalizations than their tolerant counterparts. Findings suggest primate signals are used and evolve in tandem with the nature of interactions that characterize individuals' social relationships.publishe