No armor is perfect: detecting hotspots of parasitic horse fly attacks on black caiman through 3D modeling and citizen science.

Ectoparasites often exploit anatomical weak points in their hosts, yet how their attacks are distributed across the body remains poorly understood in armored ectotherms and other organisms partly due to scarce data and the lack of spatial tools for studying parasitism on complex surfaces. This study combines citizen-science imagery with three-dimensional kernel density estimation (3D KDE) to examine 275 tabanid biting events on Melanosuchus niger, mapped onto a high-resolution 3D anatomical model. Contrary to expectations, bite intensity was unrelated to surface exposure; instead, attacks clustered in nasal and orbital regions. These findings reveal non-random, anatomy-driven parasitism and introduce a replicable spatial framework for quantifying host-parasite interactions using open-access data and morphological modeling. This complementary approach advances the ecological understanding of microhabitat selection in ectoparasites and provides new tools for exploring fine-scale interactions in elusive or logistically constrained systems.