Holderied M W, von Helversen O
Institut für Zoologie II, Friedrich-Alexander Universität, Staudtstrasse 5, DE-91058 Erlangen-Nürnberg, Germany.
Proc Biol Sci. 2003 Nov 7;270(1530):2293-9. doi: 10.1098/rspb.2003.2487.
Aerial-hawking bats searching the sky for prey face the problem that flight and echolocation exert independent and possibly conflicting influences on call intervals. These bats can only exploit their full echolocation range unambiguously if they emit their next call when all echoes from the preceding call would have arrived. However, not every call interval is equally available. The need to reduce the high energetic costs of echolocation forces aerial-hawking bats to couple call emission to their wingbeat. We compared the wingbeat periods of 11 aerial-hawking bat species with the delays of the last-expected echoes. Acoustic flight-path tracking was employed to measure the source levels (SLs) of echolocation calls in the field. SLs were very high, extending the known range to 133 dB peak equivalent sound pressure level. We calculated the maximum detection distances for insects, larger flying objects and background targets. Wingbeat periods were derived from call intervals. Small and medium-sized bats in fact matched their maximum detection range for insects and larger flying targets to their wingbeat period. The tendency to skip calls correlated with the species' detection range for background targets. We argue that a species' call frequency is at such a pitch that the resulting detection range matches their wingbeat period.
飞行和回声定位对叫声间隔施加独立且可能相互冲突的影响。只有当来自前一声波的所有回声都已到达时发出下一声波，这些蝙蝠才能明确地利用其完整的回声定位范围。然而，并非每个叫声间隔都同样适用。为了降低回声定位的高能量成本，在空中捕食的蝙蝠需要将叫声发射与它们的翅膀拍打联系起来。我们将11种在空中捕食的蝙蝠物种的翅膀拍动周期与最后预期回声的延迟进行了比较。采用声学飞行路径跟踪来测量野外回声定位叫声的源级（SLs）。源级非常高，将已知范围扩展到133分贝峰值等效声压级。我们计算了对昆虫、较大飞行物体和背景目标的最大探测距离。翅膀拍动周期由叫声间隔得出。事实上，中小型蝙蝠将它们对昆虫和较大飞行目标的最大探测范围与它们的翅膀拍动周期相匹配。跳过叫声的倾向与物种对背景目标的探测范围相关。我们认为，一个物种的叫声频率处于这样一种音高，即由此产生的探测范围与它们的翅膀拍动周期相匹配。
