Impacts Of Invasive Rats On Hawaiian Cave Resources

Although there are no published studies and limited data documenting damage by rodents in Hawaiian caves, our incidental observations during more than 40 years of surveying caves indicate that introduced rodents, especially the roof rat, Rattus rattus, pose significant threats to vulnerable cave resources. Caves, with their nearly constant and predictable physical environment often house important natural and cultural features including biological, paleontological, geological, climatic, mineralogical, cultural, and archaeological resources. All four invasive rodents in Hawai'i commonly nest in cave entrances and rock shelters, but only the roof rat (Rattus rattus) habitually enters caves and utilizes areas in total darkness. Skeletons and feces have been found in the deepest passages, sometimes over a kilometer from the nearest known entrance although the animals may have used nearby small, inconspicuous entrances. Their impacts include damage to rare native plants in cave entrances; predation on vulnerable cave-inhabiting species, such as Thaumatogryllus tree crickets, and native moths roosting in caves; destruction of the irreplaceable remains of the extinct terrestrial fauna; damage to organic material associated with cultural and archaeological resources, thereby obscuring the historical record of humans in the islands; introduction of unnatural nutrients into subterranean ecosystems via their bodies and feces allowing the colonization of caves by other harmful alien species; and disturbance of research sites. Furthermore, the extirpation of colonies of cave-roosting moths has impacted native birds nesting in the entrance and twilight zones.