Quantitative analysis of vocalizations of captive Sumatran tigers (Panthera tigris sumatrae)

Abstract

Tigers (Panthera tigris) are one of the world’s most recognizable big cats and all surviving subspecies are critically endangered. Despite the need to understand tiger behaviour in order to enhance captive care and conservation efforts, knowledge of tiger acoustic communication has relied almost entirely on aural descriptions. We measured the acoustic characteristics of multiple, distinctly different tiger sounds and linked these sounds to behavioural contexts. Remote audio recordings of five captive Sumatran tigers (P. t. sumatrae) at Taronga Zoo, New South Wales, Australia, were obtained in May–July 2014. The 331 highest quality recordings of tiger vocalizations were separated into 7 categories (‘moan’, ‘arf’, ‘mrr’, ‘growl’, ‘roar’, ‘chuff’ and ‘hiss’) and quantified regarding fundamental and peak frequencies, duration and, in some cases, harmonics or pulse rate. Classification of the most frequently uttered vocalizations was also determined with a multinomial logistic regression based on measurements of peak frequency (Hz), fundamental frequency (Hz) and duration (s). Our findings also indicate that, although loud vocalizations uttered by tigers have often been categorized as ‘roars’, ‘roaring’ is relatively rare and is used only in contexts of pain, fear and/or high aggression, while the loud ‘moan’ is likely the more commonly heard vocalization and is frequently uttered by tigers in announcement/contact contexts.