Biology subjects

Briefer, E. F.

Publications and source records attributed to Briefer, E. F..

4 recordsLinked to original sources

bioRxiv2024

Same data, different results? Evaluating machine learning approaches for individual identification in animal vocalisations

Automated acoustic analysis is increasingly used in behavioural ecology, and determining caller identity is a key element for many investigations. However, variability in feature extraction and classification methods limits the comparability of results across species and studies, constraining conclusions we can draw about the ecology and evolution of the groups under study. We investigated the impact of using different feature extraction (spectro-temporal measurements, linear and Mel-frequency cepstral coefficients, as well as highly comparative time-series analysis) and classification methods (discriminant function analysis, neural networks, random forests, and support vector machines) on the consistency of caller identity classification accuracy across 16 mammalian datasets. We found that Mel-frequency cepstral coefficients and random forests yield consistently reliable results across datasets, facilitating a standardised approach across species that generates directly comparable data. These findings remained consistent across vocalisation sample sizes and number of individuals considered. We offer guidelines for processing and analysing mammalian vocalisations, fostering greater comparability, and advancing our understanding of the evolutionary significance of acoustic communication in diverse mammalian species.

animal behavior and cognition↗

bioRxiv2024

Long distance calls: negligible information loss of seabird social vocalisations over propagation down to the hearing threshold

How well does the information contained in vocal signals travel through the environment? To assess the efficiency of information transfer in little auk (Alle alle, an Arctic seabird) calls over distance, we selected two of the social call types with the highest potential for individuality coding. Using available recordings of known individuals, we calculated the apparent source levels, with apparent maximum peak sound pressure level (ASPL) of 63 dB re 20 {micro}Pa at 1 m for both call types. Further, we created a sound propagation model using meteorological data collected in the vicinity of the little auk colony in Hornsund, Spitsbergen. Using this model, we simulated call propagation up to the putative hearing threshold of the species, calculated to equal ASPL of signals propagated to roughly one kilometre. Those propagated calls were then used in a permuted discriminant function analysis, support vector machine models, and linear models of Beechers information statistic, to investigate whether transmission loss will affect the retention of individual information of the signal. Calls could be correctly classified to individuals above chance level independently of the distance, down to and over the putative physiological hearing threshold. Interestingly, the information capacity of the signal did not decrease with propagation. While this study touches on signal properties purely and cannot provide evidence of the actual use by the animals, it shows that little auk signals can travel long distances with negligible information loss. For the animals, this could mean that they can recognize calls of the members of their social networks as far as those calls are actually audible, and support the hypothesis that vocalisations could facilitate long-distance communication in the species.

animal behavior and cognition↗

bioRxiv2022

Delayed benefits for fallow bucks: more fights decrease same day mating success, but may increase matings the next day

Dominance hierarchies help to reduce unnecessary fights and associated costs during the mating season. Fallow deer (Dama dama) typically have high levels of male-male competition and strong reproductive skew. Nevertheless, how male dominance and daily fight rates affect mating success remains unknown. We used a two-year dataset from a large population of tagged fallow deer (620-689 individuals), to calculate male dominance ranks based on their agonistic interactions prior to the mating season ( prerut), in order to then examine how rank is related to fight rates and mating success during the mating season ( rut). Overall, higher-ranked males fought at least twice a day on a higher proportion of days during the rut and secured more matings. Males engaging in more than 10 fights per day were less likely to secure a mating that same day, and those males exceeding 15 fights per day secured no matings at all. Nevertheless, males with the highest numbers of fights (i.e. 15-21 fights per day) on a given day had higher mating success on subsequent days. Although higher-ranked males secured most matings during the rut, their fight rates decreased towards the end. We propose that engaging in more fights negatively affects daily individual mating success, but may benefit mating success on subsequent days, and potentially increase long-term fitness benefits. Additionally, engaging in more fights as the rut progresses probably allows lower-ranked males to secure some matings before the availability of oestrous females ends for almost a year. SIGNIFICANCE STATEMENTFighting carries a risk of injury and high energetic costs. Male fallow deer establish dominance hierarchies, that help reduce unnecessary fights among individuals of different competitive abilities. However, whether high-ranked males fight more or less is yet unknown. By calculating social ranks of fallow bucks before the start of their mating period, we show that males of higher social status do fight and mate more during the mating season (rut). Furthermore, by investigating how investment in fights affects individual mating success that same day and the next day, we find that males that fight more cause a decrease in their immediate daily mating success, but can potentially increase their chances of mating in subsequent days. Thus, to fight more may allow males to climb the hierarchical social ladder, hence increasing longer-term fitness benefits associated to higher ranks.

animal behavior and cognition↗

bioRxiv2022

Goat kid recognition of their mothers' calls is not impacted by changes in source-filter parameters.

Features varying more between than within individuals are usually considered as potential cues for individual recognition. According to the source-filter theory of vocal production, the fundamental frequency of mammals vocalisations depends on the characteristics of the vocal folds, while formants are determined by the characteristics of the vocal tract. Goat mothers and their kids (Capra hircus) display mutual recognition, and both source-related parameters (F0) and filter-related ones (formants) have been shown to be individualised in their vocalisations. Here, we aimed to identify if these parameters (source-related parameters (F0) and/or filter vocal parameters) are used by goat kids to recognise their mothers vocalisations. To this aim, we used an algorithm to modify either F0 or formants of the calls of goat mothers to different degrees (within or exceeding the range of natural intra-individual variability), and we played back these modified calls to their kids. We did not observe any difference in the kid reactions to the modified maternal vocalisations and to the natural calls. We suggest that either: (i) fundamental frequency and formants are not involved in maternal recognition in goats; (ii) goat kids have a tolerance for variation when recognising their mothers calls that exceeds the shifts we performed; (iii) goat maternal recognition is based on other vocal features than those tested here, or (iv) goat kid maternal recognition is based on a combination of different features and might be more flexible than previously thought, such that when one main feature is modified, kids focus on other features.

animal behavior and cognition↗