Hawaiian native species are threatened by pressures from introduced plants and animals. Some of the biggest threats monitored by the MFBRP are those by feral cats, mongooses, rats and weeds.
The State of Hawai`i Department of Health estimates that there are 500,000 cats on the Island of Maui. Thousands of these are feral, non-domesticated animals left to hunt and capture prey in the wild. Feral cats (Felis catus) inhabit all forest types on the Hawaiian Islands, including wet montane forest environments such as those found in Hanawi. Cats and cat signs (scat or tracks) have been observed in Hanawi NAR and surrounding areas by Maui Forest Bird Recovery Project staff members as well as outside researchers. An analysis of cat scats found opportunistically within Hanawi has found the remains of both nestlings and adults of native and non-native bird species. Although cats generally prefer small mammal prey items, they utilize a wide range of food resources including native avifauna. Forest birds that forage in the understory, such as the po`ouli, are especially vulnerable to cat predation. Predation by feral cats has had serious negative effects on populations of insular avifauna.
The Hawaiian Islands host three non-native species of rats. Polynesian rats (Rattus exulans)
arrived with Hawaiians about 1600 years ago and since then both black rats (Rattus rattus
) and Norway rats (Rattus norvegicus
) have arrived with Europeans. Besides being a pest around human habitation and a threat to human health, these species have a large impact on the native ecosystem as both predators and competitors. Rats are agile tree climbers and at least one of the three species is found in all native habitats.
Introduced rats are known to prey on eggs, nestlings, and adults of
Hawai`i's native forest birds. Additionally, they compete with forest birds for food items such as native snails, insects, fruits, and seeds. As a result, rats are regarded as a major factor in the decline of Hawai`i's endemic forest birds and as a barrier to the recovery of endangered forest birds
The Maui Forest Bird Recovery Project controls rat populations within one study area in Hanawi Natural Area Reserve with the use of a ground-based rodenticide program. 0.005% Diphacinone is distributed throughout the area in EPA approved, waterproof bait stations.