Energy Expenditure Optimization in the Echolocation of <i> Rhinolophus nippon </i> : Evidence from Heart Rate Stability

Abstract

Title: Simple Summary Most bats use echolocation to navigate and hunt. Research on energy consumption and regulatory strategies during vocalization helps reveal how animals manage energy to achieve an optimal balance among different behavioral investments. This balance improves animals’ survival and reproductive success. To determine how bats manage energy expenditure during intense calling, we monitored five horseshoe bats (Rhinolophus nippon) across 34 sessions as they detected prey using echolocation. Using miniature sensors, we simultaneously recorded the bats’ electrocardiogram signals and echolocation calls. This allowed us to measure energy expenditure during the search and approach phases. We found that as prey moved closer, though calling increased dramatically during the approach phase, heart rate and total energy expenditure remained stable compared to the search phase. This suggests that although producing calls is energetically costly, bats possess an efficient energy-saving mechanism. When call rates increase, they often use sonar sound groups (two or more pulses together) and adjust the sound features of individual pulses. These strategies keep energy expenditure stable as task demands rise. This discovery reveals a sophisticated physiological strategy shaped by evolution. It explains how bats sustain intense night-time hunting with limited energy and offers new insight into animal adaptation to environmental pressures.