Diet, density, and distribution of the introduced greenhouse frog, Eleutherodactylus planirostris, on the island of Hawaii.

摘要

The greenhouse frog, Eleutherodactylus planirostris, native to Cuba and the Bahamas, was recently introduced to Hawaii. Studies from other invaded habitats suggest that it may impact Hawaiian ecosystems by consuming and potentially reducing endemic invertebrates. However, there have been no studies on the greenhouse frog in Hawaii. The first component of this study was to conduct a diet analysis. We conducted a stomach content analysis of 427 frogs from 10 study sites on the island of Hawaii. At each site, we also collected invertebrates using two different sampling methods: leaf litter collection and sticky traps to characterize available resources. Greenhouse frogs consumed predominantly leaf litter invertebrates. Dominant prey items consisted of Hymenoptera: Formicidae (32.4%), Acari (19.2%), and Collembola (17.4%). Greenhouse frogs consumed more Formicidae than was measured in the environment. At one study site, we estimated there were 12,500 frogs ha-1 using mark-recapture methods and greenhouse frogs consumed 129,000 invertebrates ha-1 night-1 at this site. The second component of this study was to determine the distribution of the greenhouse frog on the island of Hawaii, with a male breeding call presence/absence survey at 446 points along the major road network. The greenhouse frog was detected at 61 sites (14%), and found mostly in lowland areas, in habitats of native shrublands and forests, nonnative forests, agricultural lands, and pastures on the southwestern and eastern sides of the island. We determined detection probabilities of the greenhouse frog and the invasive coqui frog, E. coqui. Detection probability of the greenhouse frog was low on the first two surveys and improved by the third survey. Detection probability of the coqui was higher than the greenhouse frog, but overall site occupancy estimates were similar for both species. Because the greenhouse frog appears to be as widespread as the coqui, we recommend that research be conducted to investigate its impacts ecologically to determine whether control efforts should also be aimed at this species.