Correct and wrong predictions on applying the best models.

<p>Correct and wrong predictions on applying the best models.</p

Choruses analysed in this study.

<p>Choruses analysed in this study.</p

Decoding Group Vocalizations: The Acoustic Energy Distribution of Chorus Howls Is Useful to Determine Wolf Reproduction

<div><p>Population monitoring is crucial for wildlife management and conservation. In the last few decades, wildlife researchers have increasingly applied bioacoustics tools to obtain information on several essential ecological parameters, such as distribution and abundance. One such application involves wolves (<i>Canis lupus</i>). These canids respond to simulated howls by emitting group vocalizations known as chorus howls. These responses to simulated howls reveal the presence of wolf litters during the breeding period and are therefore often used to determine the status of wolf populations. However, the acoustic structure of chorus howls is complex and discriminating the presence of pups in a chorus is sometimes difficult, even for experienced observers. In this study, we evaluate the usefulness of analyses of the acoustic energy distribution in chorus howls to identify the presence of pups in a chorus. We analysed 110 Iberian wolf chorus howls with known pack composition and found that the acoustic energy distribution is concentrated at higher frequencies when there are pups vocalizing. We built predictive models using acoustic energy distribution features to determine the presence of pups in a chorus, concluding that the acoustic energy distribution in chorus howls can be used to determine the presence of wolf pups in a pack. The method we outline here is objective, accurate, easily implemented, and independent of the observer's experience. These advantages are especially relevant in the case of broad scale surveys or when many observers are involved. Furthermore, the analysis of the acoustic energy distribution can be implemented for monitoring other social canids that emit chorus howls such as jackals or coyotes, provides an easy way to obtain information on ecological parameters such as reproductive success, and could be useful to study other group vocalizations.</p></div

GLMMs obtained considering the different datasets.

<p>GLMMs obtained considering the different datasets.</p

Schematics of the production liquid ¹⁵N-labelled organic fertiliser process from the ¹⁵N maize residue.

<p>Schematics of the production liquid ¹⁵N-labelled organic fertiliser process from the ¹⁵N maize residue.</p

Fragments of chorus howls including different types of vocalizations.

<p>Fragments of chorus howl including howls (top), short vocalizations (middle), and long highly-modulated vocalizations (bottom).</p

DW, N and ¹⁵N content of the total maize biomass produced at the end of the labelling period, and the fractions used as sheep feed and as raw material for the vegetal-based organic fertiliser^*.

<p>DW, N and ¹⁵N content of the total maize biomass produced at the end of the labelling period, and the fractions used as sheep feed and as raw material for the vegetal-based organic fertiliser^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150851#t001fn001" target="_blank">*</a>}.</p

Differences between the acoustic energy distribution parameters obtained for choruses with and without pups (Mann-Whitney U tests).

<p>Differences between the acoustic energy distribution parameters obtained for choruses with and without pups (Mann-Whitney U tests).</p

Mean faeces composition (%) before incubation for B₀ determination by type of diet and period.

<p>Mean faeces composition (%) before incubation for B₀ determination by type of diet and period.</p

Comparative volumes, total N and the N concentrations among fractions, ¹⁵N excess and N recoveries of liquid vegetal- and animal-based organic fertilisers (mg·L^-1)^*.

<p>Comparative volumes, total N and the N concentrations among fractions, ¹⁵N excess and N recoveries of liquid vegetal- and animal-based organic fertilisers (mg·L^-1)^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150851#t005fn001" target="_blank">*</a>}.</p