Study On Acoustic Communication Of Cuora Mouhotii And C. Galbinfrons

In call-producing and well-hearing animals, acoustic communication is used to exchange information from sound signals, and plays an important role in their life history. Electrophysiological studies have revealed that sea turtles use acoustic communication in their behavior and have considerable auditory sensitivity to low-frequency sounds; however, there is limited knowledge of how turtles receive and respond to their environment regarding vocal signals. This dissertation explores the acoustic ecology of two Cuora species, C. mouhotii and C. galbinifrons, focusing on their vocal communication behavior, acoustic signature, biological significance,auditory capabilities, and the implications of this knowledge for their conservation.We used a digital audio recorder to record calls in the daily behavior of two Cuora spp. in a simulated environment, from June to September, in 2013 and 2014.We collected 120 and 68 effective bites of feeding calls from 12 C. mouhotii and 7 C.galbinifrons individuals, respectively, and 81 effective bites of courtship calls from 8male C. galbinifrons individuals. The acoustic bite characteristics extracted using software found all calls were a single note comprising multiple pulses, and the envelope was clearly distinguishable from the audio spectrogram. The duration and fundamental frequency of the feeding calls of C. mouhotii were 100.52 ± 43.34 ms and 258.7 ± 68.72 Hz, respectively, with a dominant frequency of 883.45 ± 163.68 Hz.For C. galbinifrons, the duration and fundamental frequency of feeding calls was132.24 ± 55.2 ms and 270.66 ± 63.4 Hz, respectively, with a dominant frequency of840.52 ± 196.47 Hz; and the call duration and fundamental frequency of advertisement calls was 216.75 ± 104.84 ms and 270.92 ± 75.38 Hz, respectively,with a dominant frequency of 569.74 ± 329.41 Hz.We used the auditory brainstem response(ABR) to record auditory frequency sensitivity and thresholds of C. mouhotii and C. galbinifrons in the Hainan Normal University laboratory from October to December, 2015. Our results showed that ABR waveforms were obtained in both Cuora spp. and showed a series of peaks contiguous with the tone pip and click stimuli with almost identical characteristics atsuprathreshold levels. The waveforms were clear at < 1 k Hz, and gradually disappeared with increased frequency. According to the data from the ABR audiogram,as the stimulating frequency increased, the threshold increased. For most frequencies between 0.2 and 0.6 k Hz, both Cuora spp. responded to the stimuli. However, C.galbinifrons showed better high-frequency hearing than C. mouhotii; C. galbinifrons detected tonal stimuli between 0.2 and 9 k Hz, whereas C. mouhotii detected tonal stimuli between 0.2 and 5 k Hz.To expound the biological significance of calls that were produced by C.mouhotii and C. galbinifrons in feeding and courtship, we used call playback to observe their behaviour and responses in their natural habitat in Diaoluoshan Village,Diaoluo Nature Reserve, Hainan Island, China, from June to October 2015. The results showed that C. mouhotii effectively responded to both feeding and advertisement calls, but C. galbinifrons did not show an effective response. When played the feeding calls, 6 turtles(33.33%) did not respond, whereas 13 did(66.67%).Two types of behavioral responses were recorded: the turtles moved away from the area, or they moved toward the model turtle. Of these, only two turtles moved toward the model(11.11%), whereas 10 turtles(55.56%) moved away.Activity rhythms reflect the nutrition and reproduction status of individuals and their relationship with their habits. To understand the mechanism of coexistence between C. mouhotii and C. galbinifrons in the wild, their daily activity and time budgets were studied using instantaneous and scan sampling in Diaoluoshan Village,Diaoluo Nature Reserve, Hainan Island, China, from June to October 2015. The results showed that both species were diurnal, and spent most of their time resting,and limited time moving and feeding. C. mouhotii showed one peak for movement(06:00–07:00 h) and feeding(10:00–11:00 h), whereas C. galbinifrons showed one peak for feeding(13:00–14:00 h), but two peaks(09:00–10:00 h and 17:00–18:00 h)for movement. The time budgets were different between the two species, in that C.galbinifrons spent considerably more time resting than C. mouhotii and less time moving and feeding. The coefficient of overlap was 0.78 for moving and 0.38 for feeding.Both Cuora spp. produced calls, which played an important role in their daily activities. Acoustic communication is the main method of signal transfer and communication with the environment and each other. Therefore, an extensive and in-depth understanding of the call characteristics and biological significance of the two turtle species are of considerable theoretical and practical significance for the conservation of endangered or threatened species.