Research On The Effect Of Bats Ear Motion Pattern On The Echo Returns

Horseshoe bats have an active ultrasonic sonar system that allows the animals to navigate and hunt prey in structure-rich natural environments. The components of this biosonar system contain unusual dynamics that could play a key role in achieving the animals’ superior sensory performance. Horseshoe bat biosonar employs elaborate baffle shapes to diffract the outgoing and incoming ultrasonic wave packets;ultrasound is radiated from nostrils that are surrounded by noseleaves and received by large outer ears. Noseleaves and pinnae can be actuated while ultrasonic diffraction takes place. On the emission side,two noseleaf parts,the anterior leaf and the sella,have been shown to be in motion in synchrony with sound emission. On the reception side, the pinnae have been shown to change their shapes by up to 20% of their total length within ～100 milliseconds. Due to these shape changes,diffraction of the incoming and outgoing waves is turned into a dynamic process. The dynamics of the diffraction process results in likewise dynamic device characteristics. If this additional dynamic dimension was found to enhance the encoding of sensory information substantially, horseshoe bat biosonar could be a model for the use of dynamic physical process in sensing technology. The study of this paper will present what is currently known about dynamic effects in bat biosonar. The findings that have been obtained so far will be discussed in the context of sensory information encoding and parallels will be drawn between biosonar and comparable engineered sensory systems such as sonar and radar.Horseshoe bats (Rhinolophidae) and the related Old World leaf-nosed bats(Hipposideridae) both show conspicuous pinna motions as part of their biosonar Behaviors among the big bats families. In the current work, the kinematics of these motions in one species from each family (Rhinolophus ferrumequinum and Hipposideros armiger) has been analyzed quantitatively using three-dimensional tracking of landmarks placed on the pinna. The pinna motions that were observed in both species fell into two categories: In "rigid rotations" motions the geometry of the pinna was preserved and only its orientation in space was altered. In "open-close motions" the geometry of the pinna was changed which was evident in a change of the distances between the landmark points. A linear discriminant analysis showed that motions from both categories could be separated without any overlap in the analyzed data set. Hence, bats from both species have two separate types of pinna motions with apparently no transitions between them. The role of the two different motions in the biosonar behaviors of the animals remain to be determined.Bats use Doppler shift compensation mechanism to track and capture prey. This paper mainly focuses on using experiments to prove that if the bats can move their ears fast enough to make large Doppler shift that can inspire that bats to start their Doppler shift compensation mechanism.