Date of Award:
Master of Science (MS)
Karen H. Beard
Non-native species are increasing globally, and with this increase, it is likely that there will be new, unique relationships found among non-natives as well as additional impacts on native species. Rats and mongooses have been introduced to islands throughout the world where they impact native species, including birds, reptiles, and amphibians. The coqui frog was introduced to Hawaii in the 1980’s, where there were already abundant rat and mongoose populations. Previous research suggests that the high densities of coqui frogs may provide enough of a new food source for mongooses and rats that their populations would grow larger than they would without coqui frogs, and that this would exacerbate the negative effects that these predators have on native birds.
We investigated whether there are relationships between coqui presence, and the local abundance of introduced rats and mongoose on the island of Hawaii. We also investigated at these 12 sites whether there were indirect effects of coquis on bird nest predation rates using camera traps on artificial nests. Finally, we interpret our results in light of an analysis of the stomach contents of mongooses and rats, and data collected from remote cameras monitoring scavengers of dead coqui frogs.
We compared abundances of mammals in coqui invaded plots and uninvaded plots. In areas where coquis were present, we found a greater number of mongooses, and less Pacific rats. Both predators consume coquis, but mongooses were more important consumers of live and dead coquis. Shifts in mongoose and rat diets were observed in coqui invaded and uninvaded plots. It may be that coqui frogs are competing with rats because we found more fruit in rat stomachs collected in coqui invaded compared to uninvaded plots. We did not observe any difference in nest predation rates with and without coquis. Our results show that the coqui may serve as novel prey and/or competitors to non-native mammals.
Hill, Shane A., "Relationships Among Invasive Coqui Frogs, the Small Indian Mongoose and Rat Species in Hawaii" (2018). All Graduate Theses and Dissertations. 7154.