Structural Classification of Wild Boar (Sus scrofa) Vocalizations

Area of Science:

• Ethology
• Bioacoustics
• Animal Communication

Background:

• Understanding species-specific vocal repertoires is crucial for determining communication system types (graded vs. discrete).
• Previous research on wild boar (Sus scrofa) vocalizations is limited, outdated, and lacks rigorous statistical analysis.
• Domestic pigs (Sus scrofa domesticus) have been extensively studied, providing a basis for comparison.

Purpose of the Study:

• To statistically classify the vocal repertoire of wild boars (Sus scrofa) using objective signal processing techniques.
• To refine and extend previous findings on wild boar vocalizations.
• To investigate the potential for graded vocal communication in wild boars.

Main Methods:

• Recording and acoustic analysis of 616 vocalizations from semi-free ranging wild boars.
• Utilizing objective signal processing techniques and advanced statistical approaches.
• Extracting four key spectral and temporal acoustic parameters: quartile Q25, duration, spectral flux, and spectral flatness.

Main Results:

• A statistically validated classification of the wild boar vocal repertoire into four call types: grunts, grunt-squeals, squeals, and trumpets.
• Identification of acoustic continuity in some vocalizations, supporting a graded communication system.
• Objective criteria were established for classifying wild boar calls.

Conclusions:

• Modern acoustic analysis provides a statistically robust classification of the wild boar vocal repertoire.
• Wild boar vocalizations exhibit characteristics of both discrete and graded communication systems.
• Grunt-squeals are highlighted for their potential role in animal welfare assessment, warranting further research into domestication effects on vocal communication.