Abstract
In farm animals, vocal analysis is accepted as a non-invasive method for assessing animal welfare in comparison to most physiological measurements. The aim of this study was to investigate the influence of different degrees of social isolation on the acoustic characteristics of stress-induced bleats from three different breeds of sheep. The experiment consisted of subjecting the animals to three different levels of social isolation during which both locomotive and vocal data were recorded. The data on locomotive behaviour was subjected to descriptive analysis while specialized acoustic software was used to measure a total of thirty-six parameters of recorded bleats. Descriptive analysis showed that the animals displayed more locomotive activity during partial isolation compared to complete isolation. Number of bleats during partial isolation was also found to be higher. The application of two-way analysis of variance showed a significant effect of isolation level and breed on both temporal and structural acoustic properties. Amplitude, power and time acoustic properties were found to affect acoustic quality of vocal responses to isolation, whereas frequency related properties were also found to be different significantly (P < 0.05) between breeds. From spectrogram analysis, the patterns of energy distribution within the calls proved to offer the most evident that differ between isolation levels and breeds. It was concluded that acoustic analysis can be helpful in revealing the affective state of socially isolated rams. Key Words: Sheep, Social Isolation, Vocalization, Behaviour, Animal Welfare
Highlights
Acoustic communication has been found to play an important role in the social life of many animals
A General Linear Mixed model (GLM) analysis was used to investigate the effect of breed and level of isolation on the measured acoustic parameters
Based on the results obtained in this study it can be concluded that different levels of social isolation induce different behavioural and vocalization responses in rams from different breeds
Summary
Acoustic communication has been found to play an important role in the social life of many animals. Communicative behaviour occurs in any form of social interaction and implies an exchange of information between at least two individuals: a signaler and a receiver. The acquisition and the use of information helps animals to anticipate and respond appropriately to events, and to increase their survival (Owings et al 1997). Engeldal et al Effect of different levels of social isolation on the acoustical characteristics of sheep vocalization. According to De Lucia et al (2010) vocalizations are essential in communication and social interactions, conveying the speaker’s identity, gender, intentions, and emotional state. Information is made available by signals that vary in relation to the type of information delivered and to the surrounding environment (Vannoni et al 2005)
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