Evaluating Thermal Infrared Drone Flight Parameters on Spider Monkey Detection in Tropical Forests

Area of Science:

• Wildlife conservation
• Remote sensing technology
• Primate ecology

Background:

• Geoffroy's spider monkeys are endangered, arboreal primates facing survey challenges due to their habitat and social behavior.
• Drones with thermal infrared cameras offer a potential solution for surveying elusive species like spider monkeys.

Purpose of the Study:

• To assess the impact of drone flight parameters on spider monkey detectability.
• To evaluate inter-coder agreement in analyzing drone-recorded thermal infrared videos.
• To inform standardized protocols for drone-based wildlife surveys.

Main Methods:

• Generalized linear mixed models were used to analyze the effect of flight speed (2-6 m/s), height (40-50 m), and camera angle (-45°, -90°).
• Surveys were conducted in a closed-canopy forest in Mexico using a drone equipped with a thermal infrared camera.
• Fleiss' kappa coefficient was used to measure coder agreement.

Main Results:

• No tested flight parameters (speed, height, camera angle) significantly affected the number of detected spider monkeys.
• Substantial agreement (kappa = 0.61-0.80) was observed between coders, particularly in high thermal-contrast areas.
• Drone surveys show promise for monitoring spider monkey populations.

Conclusions:

• Standardized flight protocols are crucial for accurate wildlife population data collection.
• Recommended drone survey parameters include 4 m/s speed, 15 m above canopy height, and a -90° camera angle for spider monkeys and similar mammals.
• Optimal parameters may vary based on drone model characteristics (size, noise).