Time and habitat structure shape insect acoustic activity in the Amazon

Area of Science:

• Ecology
• Bioacoustics
• Insect Ecology

Background:

• Insects are Earth's most diverse animal taxon, crucial for ecosystem functioning.
• Monitoring hyper-diverse insects is challenging, often neglected in ecological surveys.
• Technological advances in biomonitoring offer new solutions for insect monitoring.

Purpose of the Study:

• Investigate insect acoustic activity using passive acoustic monitoring in Viruá National Park, Brazil.
• Describe frequency ranges of soniferous insects (cicadas, crickets, katydids) and calculate the acoustic evenness index (AEI).
• Assess spatial and temporal AEI variations across habitats and relate AEI to vegetation structure.

Main Methods:

• Conducted passive acoustic monitoring at 141 sites across eight habitats.
• Analyzed frequency ranges and acoustic activity of cicadas, crickets, and katydids.
• Calculated the acoustic evenness index (AEI) and correlated it with habitat and vegetation variables.

Main Results:

• Crickets occupied lower, narrower frequency bands than cicadas and katydids.
• Acoustic activity varied significantly across insect groups, space, and time.
• Highest acoustic activity was observed before sunrise; lowest was in pastures. Canopy cover positively correlated with cricket activity.

Conclusions:

• Acoustic evenness index (AEI) is a valuable metric for assessing insect activity.
• Time, habitat type, and vegetation structure significantly influence insect acoustic activity.
• Passive acoustic monitoring provides insights into insect biodiversity and ecological roles in Amazonian ecosystems.