Geographical Variation In Echolocation Calls Of Four Horseshoe Bats

Echolocation is an important part in bats daily activities. The echolocation calls can be used to detect the target, positioning, predation, navigation, etc., as well as an important way to communicate between bats. The echolocation calls contain a lot of information. However, the information contained in the echolocation calls is not static, bats use different echolocation calls in different prey stages. The complexity of the environment can affect the bats emit echolocation calls because of its plasticity. There are some differences in the geographical isolation of bat echolocation calls, presenting idioms. The significance of this difference and the causes are acoustic research focus. This study is conducted in 2013 and 2014, investigating the differences of echolocation calls structure among geographical populations of four Rhinolophus: least horseshoe bat (Rhinolophus pusillus), greater horseshoe bat (Rhinolophus ferrumequinum), Chinese rufous horseshoe bat (Rhinolophus sinicus), and intermediate horseshoe bat (Rhinolophus affinis), from a relative large scale. Furthermore, we explored the factors that cause the sound differences among different geographical populations by Pearson correlation.The results showed that female of R. pusillus were slightly larger than males, and the dominant frequency of females was higher than that of males. The echolocation calls among 9 geographical populations shown a certain degree variations in pulse duration, pulse interval, frequency, and bandwidth. Forearm length and body mass of females were both negatively correlated with their dominant frequency (FA:r=-0.281, P=0.032; Mass:r=-0.371, P=0.004), and the rainfall and the dominant frequency were positively correlated (r=0.853, P=0.007). But the echolocation calls of males have no correlations with forearm length, body mass, and rainfall. In additionally, the echolocation parameters of both males and females have no correlations with geographical distance, temperature, and humidity.The body size (forearm and body mass) between females and males of R. ferrumequinum (5 geographic populations), R. sinicus (6 geographic populations) and R. affinis (5 geographic populations) was not significantly different. The dominant frequencies of females were higher than those of males in R. ferrumequinum and R. sinicus, but there is no significant difference between frequencies of males and females in R. affinis. Different geographic populations showed a significant difference in echolocation calls (dominant frequency) among these three bat species, while the causes are inconsistent. The echolocation calls of R. ferrumequinum have no correlations with temperature, humidity and body size. In R. sinicus, body mass was positively correlated with their dominant frequency (male:r=0.714, P=0.000; female: r=0.573, P=0.000). The annual average temperature and the dominant frequencies of males and females were negatively correlated (r=-0.857, P=0.029; r=-0.924, P=0.000, respectively). But the echolocation calls have no correlations with forearm length and rainfall. Forearm length and body mass of R. affinis were both negatively correlated with their dominant frequencies (r=-0.339, P=0.012; r=-0.589, P=0.000, respectively). Temperature and humidity have no correlations with dominant frequency.The results of this study showed that the echolocation calls of four Rhinolophus bat species are significant differences among different geographic populations, indicating there are idioms in different geographic bat populations. But the main causes to idioms in different bat species may be difference. Body size, rainfall, and temperature are the main factors. From these results, we deduced that the echolocation calls varied among different geographic populations of horseshoe bat, which might be mainly effected by local habitats, such as rainfall. This variation exhibits adaptive evolution when the animals live in different habitats.