Diets And Coexsistence Of Two Sympatric Morphologically Similar Horseshoe Bats Using Similar Echolocation Calls

The morphology, echolocation, diet and foraging time of two sympatric morphologically similar horseshoe bats (Rhinolophus sinicus and R. affinis) were studied. We analyzed the spatial niche, trophic niche and temporal niche of the two species, and concluded the stably coexistent reasons in the same cave. The main results were as follows:1. R. sinicus and R. affinis are both middle sized horseshoe bats (forearm length: 50-55 mm). No sexual morphological difference was discovered in R. sinicus and R. affinis. But there were significant differences on forearm length, body weight and wing load, and other parameters such as wing length and wing span were not significantly different. D3 was not significant difference, but R. affinis had a significant higher D5 value, and also had a higher aspect ration and a lower wing load. So we conclude that R. affinis may fly higher and more manoeuvrable, and forage in more complex vegetation than R. sinicus. Spatial niche partitioning may occured between them.2. Echolocation calls of R. sinicus and R. affinis emitted when hanging were both typical FM-CM-FM, with peak frequency 78-85 kHz (R. sinicus: 79.6-84.2 kHz, R. affinis: 83.4-85.4 kHz). The calls usually included 1-2 harmonics and 3-4 pulses. Obvious significant sexual difference was found in R. affinis but not in R. sinicus, and interspecific difference was greater than intraspecific difference. The peak frequencies of R. sinicus and R. affinis were significant different, and the wave lengths were 4.24 and 4.11, respectively. According to allotonic frequency hypothesis, the prey size would be similar between them. The small differences of echolocation calls between R. sinicus and R. affinis may not enough to lead to trophic partioning of them.3. Fecal analysis discovered that Lepidiptera, Coleoptera, Hymenoptera, Diptera and Homoptera composed the main diet of R. sinicus and R. affinis (total volume percent>90%), small percentage of Hemiptera, Neuroptera, Orthoptera and Trichoptera were discovered, also include small percentage of unidentified insects (volume percent<0.2%). Only significant difference was found between R. sinicus and R. affinis by choosing Lepidiptera insects. Niche breadths were respectively 2.38 and 2.28 for R. sinicus and R. affinis, and niche overlap was 0.907. So the trophic niche was highly overlapped. There was no significant difference of prey size selection between the two horseshoe bats, also no obvious temporal partioning was discoverd.