Non-native introduced mammalian predators negatively impact native bird populations across the Hawaiian Islands, contributing to species’ decline. Most native birds are naïve to mammalian predators, lacking evolutionary adaptations. Cats, rats, and mongooses were all introduced to the Hawaiian Islands by humans. They are prolific predators as well as disease vectors and are known to be a source of biodiversity loss and ecosystem degradation in multiple locations around the world.
They prey upon native adult birds, eggs, and nestlings. Native bird species that nest on the ground, like the Nēnē (Hawaiian Goose) or ‘ua’u (Hawaiian petrel), are particularly vulnerable. But these predators can also climb trees impacting the Hawaiian forest birds as well.
These invasive species inhabit most environments on the Hawaiian Islands, including wet, montane forests where native forest birds are found. Predator control is an essential component to endangered species and habitat management in Hawai‘i. Across the islands and elsewhere, predator control programs reduce these invasive species populations and help protect nesting native birds.
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Three non-native rat species were introduced to Hawai’i: Polynesian rats (Rattus exulans) arrived with Hawaiians about 1600 years ago. Black rats (Rattus rattus) and Norway rats (Rattus norvegicus) arrived with Europeans. Besides being a pest around human habitation and a threat to human health (see Rat Lungworm), these species have a large impact on the native ecosystem as predators and competitors. In addition to impacting birds, rats also eat native snails, insects, fruits, and seeds. This decreases plant recruitment and regeneration of the forest and can decrease populations of snails and insects.
The Small Indian Mongoose (Urva auropunctata) is a native of Asia and was introduced to Hawai’i in 1883 to control rodent populations in the Hawaiian sugar cane fields. The introduction resulted in a slight reduction of rodent numbers but failed to have a significant impact on these populations.
Our team has observed mongooses climbing up trees and even eating from ‘Apapane nests in high elevation forests.
There is a growing population of feral, free-roaming, non-domesticated cats (Felix catus) in Hawai‘i. These cats hunt and capture prey in the wild impacting native birds from mauka to makai. Our team has observed cat scat and sign in the native forests on Maui. Unfortunately, we even found birds that have been killed by cats, including a kiwikiu.
These cats are the product of decades of abandoned animals. You can help by being a responsible pet- owner as well as not supporting feral cat colonies and Trap-Neuter-Return (TNR) programs. See Keeping Cats Indoors and support better cat management. Feral, free-roaming cats are often susceptible to diseases such as toxoplasmosis and feline leukemia, collisions with cars, and fighting or competing with other wildlife. Diseases that feral cats carry not only threaten the health and safety of Maui’s citizens but can also lead to death to birds and even marine life.
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