Meso-mammal behavior and resource use in central Texas caves

Authors: Andrea E. Montalvo, Roel R. Lopez, Israel D. Parker, Nova J. Silvy, Susan M. Cooper & Rusty A. Feagin

Meso-mammals are frequent cave visitors whose role in cave ecology is poorly understood. Determining typical behaviors and motivations of meso-mammal cave use is essential for management of natural resources found within these unique ecosystems. This is especially important at Joint Base San Antonio–Camp Bullis (hereafter Camp Bullis), where many of the caves are actively managed for United States federally endangered arthropods (e.g., Cicurina madla, Rhadine exilis, Rhadine infernalis). Specifically, we sought to determine what meso-mammal behaviors were performed in caves, according to species, season, and time of day. We set trail cameras to record video throughout the passages of each cave, for one month each season. Our data supports previous studies that suggest herbivorous North American porcupines (Erethizon dorsatum) largely use caves for denning and grooming, while omnivorous Virginia opossums (Didelphis virginianus) and raccoons (Procyon lotor) use caves to feed on arthropods. Two noteworthy behaviors are the consumption of arthropods, which may include endangered species, and the deposits of North American porcupine scat. Meso-mammal scat serves an important function in a cave’s ecosystem by bringing in nutrients that support cave-obligate species. Texas caves likely evolved with raccoons serving this function. Though North American porcupine have only recently expanded their range into central Texas, their scat is far more abundant than relatively uncommon raccoon scat, even in caves with regular raccoon visitation. The additional nutrients of North American porcupine scat into caves could lead to extirpation of the endangered arthropods and other cave-adapted species through the invasion and settlement of more competitive or predatory terrestrial species. We suggest cave managers begin monitoring meso-mammal cave use including changes in the rate of consumption of arthropods and scat deposition to better understand long-term cave system dynamics.

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