Networking Strategies used by Bats to Improve Social Sonar
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abstract
The biosonar behavior of echolocating bats provides an example of how natural and artificial active sensing systems may be optimized to meet rapidly changing social and environmental conditions. Bats and artificial sonar, radar and communication systems all face a similar suite of problems arising from mutual interference. Explaining how bats minimize interfering with one other''s sonar while flying in dense swarms or within noisy crowded roosts may help improve a wide range of artificial sensing and wireless communications systems. Bats are highly social and their exceptional resilience to jamming by conspecifics far exceeds the strategies currently employed in artificial systems. This proposal will investigate how groups of bats manage this by applying recent advances in computer networking to sonar/radar theory. The experiments outlined will characterize the behavioral strategies used by bats to improve their signaling efficiency when echolocating in groups of different sizes and across tasks of varying navigational demands. Computer simulations will be used to identify optimum algorithm parameters and explore how these behavioral strategies manifest across a wider range biosonar conditions. By deciphering the behavioral algorithms by which bats can cooperatively share the same acoustic space this proposal may lead to better and more efficient strategies for optimizing artificial communications network usage to support an increasingly information-based economy. This proposal will also offer unique exposure, training and educational opportunities for STEM students interested in exploring biological systems as a source of inspiration for artificial systems. In partnership with local science teachers, this proposal creates an inquiry-based dual language (Spanish/English) teaching website that will offer access for 5th/6th grade science classes to remotely interact with live animals.Interference problems arise in artificial systems such as sonar and radar, wireless communications and computer network when many users attempt to transmit simultaneously over a single shared channel. Wireless communications networks partially mitigate this by employing protocols constraining user transmission rates during periods of high channel traffic to minimize interference rates between users. This proposal tests the hypothesis that echolocating bats adapt their sonar pulse emission rates to optimize sonar performance in social situations following protocols similar and applicable to international standards in wireless communications systems. The proposal uses a combination of behavioral studies with bats in the lab and computer simulations to decode the bat''s retransmission delay algorithm. First, trained bats are flown alone and in small groups of 2-5 through a sensor maze to quantify the bats'' navigational performance and measure whether they systematically change pulse emission rates when performing the same task in a social context. Secondly, bats will be flown through the maze in the presence of artificial acoustic stimuli mimicking the sounds of other bats passing through the maze to test whether bats can realize a net improvement in sonar performance by decreasing their own pulse emission rates proportional to population density, counterintuitively reaping a net increase in information flow by emitting fewer pulses. Computational models of the behavioral algorithm will be developed to simulate the behavior, establish optimal parameters and precisely quantify its benefits to sonar performance in social contexts. The bat''s sonar algorithms will be made available through scientific journals and Matlab-based biosonar simulation tools developed for the project will be made freely available via multiple sources on the Internet.
