Detection of South American porcupines (Rodentia: Erethizontidae) by thermal drones: A new opportunity for surveying and monitoring of elusive species

Studying elusive, nocturnal and arboreal mammals such as the Neotropical porcupines (Erethizontidae) is logistically challenging, as traditional visual censuses often require many hours to detect an individual. Such logistical constraints have resulted in a knowledge gap about this group, highlighting the need for new survey approaches such as drones. We evaluated the feasibility and detection performance of thermal drones for arboreal porcupines and contextualized their performance relative to ground-based visual searches in different fragments of Atlantic Forest in four Brazilian states. Eighteen individuals of three species ( Coendou baturitensis, C. spinosus, and Chaetomys subspinosus ) were recorded: nine during 4,414 minutes of ground searches and nine during 198 minutes of drone flights. Drone-assisted surveys showed shorter median time to first detection (8.0 min) compared to diurnal ground surveys (132.5 min), substantially reducing search time per detection. These findings extend the known western distribution of C. subspinosus, and demonstrate that thermal drones are a non-invasive and time-efficient complementary tool for surveying arboreal mammals in structurally complex forests.