Ecologia acústica de pares fêmea-filhote de baleia franca austral (Eubalaena australis) (Desmoulins, 1822) em águas costeiras do estado de Santa Catarina, Brasil

Abstract

Remote acoustic sensing has been used to investigate several aspects of cetacean ecology and behaviour as occurrence, population density and impacts of anthropogenic sounds on communication systems. Nonetheless, the efficiency of PAM methods depends on the ability of researchers to detect and interpret acoustic signals and therefore on baseline information about natural features of the target species’vocal behaviour. The coastal waters off the state of Santa Catarina, Brazil, are an important wintering ground for Southern right whales (Eubalaena australis). Right whales aggregates in this area year after year, between July and November and protection measures are due to ensure the safety and health of this population. Aiming to build the required knowledge to use PAM as a right whale conservation and research tool in Brazil, the objective of the present study is to gather information concerning the acoustic ecology of right whale mother-calf pairs off Santa Catarina. Bottom-mounted archival acoustic recorders were deployed in two locations at the Right Whale APA during the wintering season. 1427 right whale calls with SNR≥ were classified in 7 call classes accordingly to visual and aural characteristics: upcall (55.8%), downcall (12.9%), down-up call (12.3%), tonal constant (10.1%), tonal variable (6.7%), hybrid (1.6%)and pulsive (0.6%). Mean values of start, end, maximum and minimum frequencies, frequency bandwidth, peak frequency and duration were calculated. Temporal pattern analysis revealed no significant diel trend in the emission of contact calls (Kruskal-Wallis test chi-square=5.86, df=3, P=0.12). Results may be linked to the predominant behavioral of whale groups through the period of stay at the wintering area. Using synched surface-behavioral observations and acoustic recordings, calling rates were obtained and the use of call classes in different behavioral states was discussed. Callingrates (call/min) were associated with the activity level of mo/ca pairs, greater in interactions and bonding and lower during travelling and resting. No calls were attributed to diving or nursing pairs. Upcalls and down-upcalls calls were attributed to resting pairs as well as traveling pairs. Constant calls were detected when a pair was swimming toward the research boat and pulsive calls were detected in the presence of dolphins in close proximity to the dislocating focal group. Interestingly, mo/ca pairs spend 20% of the sampling time interacting with other pairs and the greatest diversity of calls was recorded during such events. Pulsive (12%) and hybrid calls (13%-exclusively recorded during mo/ca interactions) are characteristics of agonistic behavior between whales. When bonding, mother and/or calves produced exclusively upcalls.The adaptative significance of previously described calls in mother-calf pair ́s communication is similar to what has been described for other whale groups.This dissertation brings significant information that constitutes bases of right whale bioacoustics in Brazil, and therefore will be vital for the implementation of mitigation, monitoring and investigation tools based on acoustic principles. Moreover, it contributed to fulfil the lack of behavioural and acoustic data of mother-calf pairs a highly vulnerable and vital subgroup for all right whale populations.