Relationship among call variables and environmental factors, call property differences between Bd infected and non-infected groups, and territoriality in Hyla japonica

Hyla japonica;Batrachochytrium dendrobatidis;emerging infectious disease;amphibians;bioacoustics;territoriality;570

자연과학대학 생명과학부 ;

University:서울대학교 대학원

关键词: Hyla japonica;    Batrachochytrium dendrobatidis;    emerging infectious disease;    amphibians;    bioacoustics;    territoriality;    570;   

Others  :  http://s-space.snu.ac.kr/bitstream/10371/131569/1/000000020802.pdf

美国|英语

来源: Seoul National University Open Repository

【 摘 要 】

Although there are different types of signals other than vocalization used in amphibian reproductive behavior, acoustic signal is one of the most common and dominant means of anuran amphibian communication and male frog’s advertisement call plays an important role in mate choice. Nevertheless, sound production requires a lot of energy and male frog’s sound producing behavior and acoustic signaling patterns can be influenced by many different intrinsic or exogenic factors. Meanwhile, chytridiomycosis, which is caused by Batrachochytrium dendrobatidis (Bd) has led to dramatic population decline and extinction in several amphibian species since it was first found in the late 1990s. Although such massive population decline has not been reported in Korean amphibian species, recent studies documented certain level of Bd prevalence in Korea, and treefrog (i.e. Hyla japonica), one of the most commonly found anuran amphibian species in Korea was not an exception. Considering all these factors, Bd infection could have affected treefrog sound producing behavior or quality of acoustic signals. In this study, I mainly tried to see whether there is any difference in acoustic signals between Bd infected and Bd non-infected groups of individuals. At the same time, to figure out potential relationships among call properties and environmental factors, and territoriality of treefrog, additional analyses were performed. In previous studies, female frogs exhibited preference towards certain qualities of call properties, such as call duration and dominant frequency, and these call characteristics were demonstrated as important criterion when it comes to female frog’s mate choice. If there is any Bd-induced difference in treefrogs’ advertisement calls, and such acoustic changes took place in the quality of major criterional call properties, this could possibly lead to female’s frogs mate choice behavior and potentially affect overall sexual selection mechanism in treefrog reproductive behavior. The result showed that note repetition rate and pulse repetition rate were in positive relationship with atmospheric temperature, and dominant frequency was in negative relationship with snout-vent length. Though this does not indicate any causal effect of environmental factors, we can expect that the speed of note production will move in the same direction as temperature changes. Also negative relationship between snout-vent length and dominant frequency is consistent with what was found from the preceding studies. In general anuran communication, the dominant frequency of sound is determined by the size, tension of the vocal cord and the force of air flow coming from the lung, and larger-size males are likely to have bigger and thicker vocal cord. Considering all these factors, dominant frequency in an inverse relationship with snout-vent length is quite predictable. When compared call properties of Bd infected and non-infected groups, call duration showed quite notable difference between two groups. However, when t-test was performed to predict the difference between the populations of two groups, only NRR showed significant difference between them. Also when compared linear associations among call properties and environmental factors of two groups, the effect of ND (note duration) on NRR (note repetition rate) and the effect of AT (atmospheric temperature) on ND (note duration) were both greater in non-infected group. The result indicated that Bd infected individuals make notes at a lower speed than non-infected individuals and Bd infected individuals’ call properties are less influenced by atmospheric temperature and note duration. This could suggest that some of the call properties might have been affected by Bd infection but still, further studies are required to figure out more precise relationship between Bd infection and quality of calls. Lastly, the coefficient of variation in rice paddy numbers was used to speculate on the territoriality of treefrog and 10 out of 21 recaptured individuals were found in the same rice paddy. Though this cannot be a profound evidence to show the territoriality of treefrog, we can expect that the range of their movement is somewhat limited.