Intraspecific variation in vocal repertoire among dugong populations

Previous studies have demonstrated that vocal signals facilitate acoustic communication of dugongs. We recorded wild dugong calls from around Talibong Island, Thailand (n = 586) and in Moreton Bay, Australia (n = 331). We also recorded vocalizations of a newborn calf (n = 315) kept at Phuket Marine Biological Center, Thailand, a 19 year old female (n = 73) at Toba Aquarium, Japan, and a 7 year old female (n = 203) at Underwater World, Singapore. Dominant frequency, duration and coefficient of frequency modulation were compared across populations and age. Statistical differences were found for almost all pairwise comparisons (p < 0.05) except between the captive dugongs kept in Japan and also between wild dugongs in Thailand and in Australia. A negative correlation was found between variance of the dominant frequency and dugong age, and a positive correlation was found between variance of the duration and age. The average dominant frequency of wild dugong calls collected in Thailand and in Australia were 5...