Chinese striped-neck turtles vocalize underwater and show differences in peak frequency among different age and sex groups

Abstract

Background Turtle vocalizations play an important role throughout their lives by expressing individual information (position, emotion, or physiological status), reflecting mating preferences, and synchronizing incubation. The Chinese striped-neck turtle (Mauremys sinensis) is one of the most widely distributed freshwater turtles in China, whose wild population is critically endangered. However, its vocalization has not been studied, which can be the basis for behavioral and ecological studies. Methods Five different sex–age groups of turtles were recorded underwater in a soundproof room. Cluster analysis and principal component analysis for classification of Chinese striped-neck turtle calls were unreasonable. The turtle calls were manually sought using visual and aural inspection of the recordings in Raven Pro 1.5 software and classified according to differences perceived through auditory inspection and the morphological characteristics of the spectrograms. The results of similarity analysis verified the reliability of manual classification. We compared the peak frequency of the calls among different age and sex groups. Results We identified ten M. sinensis call types, displayed their spectra and waveforms, and described their auditory characteristics. Most calls produced by the turtles were low-frequency. Some high-frequency call types, that are common in other turtle species were also produced. Similar to other turtles, the Chinese striped-neck turtle generates harmonic vocalizations. Courtship behaviors were observed when one of the call types occurred in the mixed-sex group. Adult females produced more high-frequency call types, and subadult males had higher vocalizations than other groups. These results provide a basis for future research on the function of vocalizations, field monitoring, and conservation of this species.

Hidden social complexity behind vocal and acoustic communication in non-avian reptiles

“…It is also worth noting that these free-moving turtles were only one-month-old suggesting that vocal complexity may increase during development and highlighting the necessity of studying the use of sounds in turtles across different life stages. Moreover, studies in freshwater turtles that were living in captivity as a group found that the use of sound types varies by sexes and ages [48][49][50]. These findings support our expectation that turtles have wider use of sounds in their underwater lives and suggest the potential of social communication by acoustic signals in turtles.…”

“…Thereafter, research in both sea turtles and freshwater turtles has revealed that eggs emit sounds during hatching, which may enable the synchronization of hatching among siblings (figure 2; table 2). The underwater sounds produced by turtles have recently been investigated in a handful of freshwater or marine turtle species (table 2), either free-ranging [38] or living in a group with conspecifics in captivity [39,42,43,[47][48][49]. When living in a group, the use of sound types can vary by sex and age [47][48][49], which The number of records of using sounds in behavioural contexts in non-avian reptiles over the past two decades.…”

“…The underwater sounds produced by turtles have recently been investigated in a handful of freshwater or marine turtle species (table 2), either free-ranging [38] or living in a group with conspecifics in captivity [39,42,43,[47][48][49]. When living in a group, the use of sound types can vary by sex and age [47][48][49], which The number of records of using sounds in behavioural contexts in non-avian reptiles over the past two decades. Each circle represents the number of records using sounds in that behavioural context and in that reptile taxon, and the size of circle is in proportion to the number.…”

“…The underwater sounds produced by turtles have recently been investigated in a handful of freshwater or marine turtle species (table 2), either free-ranging [38] or living in a group with conspecifics in captivity [39,42,43,47–49]. When living in a group, the use of sound types can vary by sex and age [47–49], which suggests that underwater acoustic communication could convey information about the sender (i.e. their sex or age), and thus may have a social function, but this needs further empirical examination.…”