Invasive Mammals of the Pacific
The terrestrial biota of the Central Pacific is primarily defined by its degree of isolation. At the center lies the Hawaiian Archipelago, which is more than 3,200 km from any continental land mass. After tens of millions of years of evolutionary isolation from all mammals except bats, islands of the Central Pacific were quite suddenly besieged by a number of alien rodents, carnivores and both large and small herbivores. The first mammals were introduced by early canoe voyagers of the Pacific more than 1,000 years ago. The discovery of the Hawaiian Islands by Cook in 1778, like many other islands of the Pacific, marked the second wave of introductions of many hoofed animals for beasts of burden, milk, hides and meat as well as small predators to keep an assortment of stowaway rodents at bay.
Overview:
The terrestrial biota of the Central Pacific is primarily defined by its degree of isolation. At the center lies the Hawaiian Archipelago, which is more than 3,200 km from any continental land mass. After tens of millions of years of evolutionary isolation from all mammals except bats, islands of the Central Pacific were quite suddenly besieged by a number of alien rodents, carnivores and both large and small herbivores. The first mammals were introduced by early canoe voyagers of the Pacific more than 1,000 years ago. The discovery of the Hawaiian Islands by Cook in 1778, like many other islands of the Pacific, marked the second wave of introductions of many hoofed animals for beasts of burden, milk, hides and meat as well as small predators to keep an assortment of stowaway rodents at bay.
Rapid ecological degradation ensued and whole groups of endemic plants and animals suffered extinctions, including virtually all flightless birds, and roughly nine percent of all Hawaiian flora. After a century of settlement by westerners, the concept of eradicating non-native species came about as a solution to primarily agricultural, public health, or economic problems, and only more recently to solve ecological problems. Reversing the devastating effects of alien mammals has proven to be difficult, but limited successes have resulted in the dramatic recovery of native biota.
Mammals General Overview
Most of the isolated islands of the Pacific existed for tens of millions of years in the absence of terrestrial mammals except for bats, which were able to fly over vast oceans and establish themselves. The first human colonists of these islands brought with them domestic pigs (Sus scrofa) from island southeast Asia and Polynesian rats (Rattus exulans). European colonists brought an assortment of other mammals with them nearly 1,000 years later, including domestic goats (Capra hircus), sheep (Ovis aries), cattle (Bos taurus), other types of wild and domestic pigs, cats (Felis catus), rabbits (Oryctolagus cuniculus), rats (R. rattus and R. norvegicus), and mice (Mus musculus). In the absence of natural predators and competitors, these species became abundant on nearly every island, which caused rapid ecological degradation. Native plants of the islands were poorly defended against the newly established herbivores, and native wildlife were naïve to tree-climbing predators with teeth. Species which had never been previously domesticated such as axis deer (Axis axis), European mouflon sheep (O. musimon), and mongooses (Herpestes javanicus) were brought to the islands later and proved to be particularly challenging to manage. Diseases associated with introduced mammals such as toxoplasmosis (Toxoplasma gondii), bovine tuberculosis (Mycobacterium bovis), and bubonic plague (Yersinia pestis) have all caused major problems for wildlife, livestock, and human health in Hawai‘i. Invasive mammals have caused the decline and extinction of numerous native plants and animals, but researchers and land managers have developed progressively more effective strategies for managing these species, allowing the recovery and restoration of native species in increasingly larger natural areas.
Small Mammal/Toxoplasmosis Overview
Many factors have contributed to the decline and extinction of birds in Hawai‘i, not the least of which has been introduced mammalian predators like rats, mongooses, and cats. These predators take eggs, kill nestlings, or nesting adults, but are also sources of diseases that kill birds. One such disease known as toxoplasmosis can cause severe developmental disabilities and occasional mortality in humans but can also have lethal consequences for marine mammals. The infectious agent of the disease, Toxoplasma gondii, is a protozoan, a single-celled organism which behaves like an animal. It is considered a parasite, causing infection directly rather than by producing toxins. It is a zoonosis because it is a disease of animals that can also be transmitted to humans. Only cats –regardless of whether they are domestic or wild species– can support sexual reproduction of this parasite, and thereby serve as the definitive host of the disease. Any other warm-blooded animal, most commonly rodents, can also carry the parasite but can only serve as an intermediate host. Intermediate hosts of the parasite and may sometimes be consumed by people, leading to infection. Known intermediate hosts include feral pigs (Sus scrofa) and mouflon sheep (Ovis musimon), both popular game mammals in Hawai‘i. Birds can also be intermediate hosts, and populations that have been infected and killed by T. gondii include the critically endangered ‘Alalā (Corvus hawaiiensis), the endangered Nēnē (Branta sandvicensis), Red-footed Booby (Sula sula), and Erckel’s Francolin (Pternistis erckelii), a common gamebird. Flowing water may transport T. gondii oocysts –hardy, thick-walled, environmentally resistant spores– in runoff from land to streams and then into marine environments. Thus, T. gondii represents a land-based pathogen that can pollute nearshore marine ecosystems and infect a wide variety of animals in this environment including whales, seals dolphins, and sea otters. The leading cause of death of the endangered Hawaiian monk seal (Monachus schauinslandi) is now known to be T. gondii infection. Many aspects of T. gondii are poorly understood, but current research may soon lead to more effective management strategies to protect native wildlife from both toxoplasmosis and predation.
Below are publications associated with this project.
The risk of rodent introductions from shipwrecks to seabirds on Aleutian and Bering Sea islands
Accidental introductions of rodents present one of the greatest threats to indigenous island biota, especially seabirds. On uninhabited remote islands, such introductions are likely to come from shipwrecks. Here we use a comprehensive database of shipwrecks in Western Alaska to model the frequency of shipwrecks per Aleutian and Bering Sea island, taken as a proxy for the threat of rodent introduct
Biology and impacts of Pacific Islands invasive species. 14. Sus scrofa the feral pig (Artiodactyla: Suidae)
Feral goats and sheep
Monitoring eradication of European mouflon sheep from the Kahuku Unit of Hawai‘i Volcanoes National Park
Conversion of native terrestrial ecosystems in Hawai‘i to novel grazing systems: a review
Federal collaboration in science for invasive mammal management in U.S. National Parks and Wildlife Refuges of the Pacific Islands
A tour de force by Hawaii’s invasive mammals: Establishment, takeover, and ecosystem restoration through eradication
Changes in habitat use and distribution of mouflon in the Kahuku Unit of Hawai‘i Volcanoes National Park
Abundance, distribution, and removals of feral pigs at Big Island National Wildlife Refuge Complex 2010–2015
Evaluating detection and monitoring tools for incipient and relictual non-native ungulate populations
Home range use and movement patterns of non-native feral goats in a tropical island montane dry landscape
Vegetation and non-native ungulate monitoring at the Big Island National Wildlife Refuge Complex 2010–2014.
Below are partners associated with this project.
The terrestrial biota of the Central Pacific is primarily defined by its degree of isolation. At the center lies the Hawaiian Archipelago, which is more than 3,200 km from any continental land mass. After tens of millions of years of evolutionary isolation from all mammals except bats, islands of the Central Pacific were quite suddenly besieged by a number of alien rodents, carnivores and both large and small herbivores. The first mammals were introduced by early canoe voyagers of the Pacific more than 1,000 years ago. The discovery of the Hawaiian Islands by Cook in 1778, like many other islands of the Pacific, marked the second wave of introductions of many hoofed animals for beasts of burden, milk, hides and meat as well as small predators to keep an assortment of stowaway rodents at bay.
Overview:
The terrestrial biota of the Central Pacific is primarily defined by its degree of isolation. At the center lies the Hawaiian Archipelago, which is more than 3,200 km from any continental land mass. After tens of millions of years of evolutionary isolation from all mammals except bats, islands of the Central Pacific were quite suddenly besieged by a number of alien rodents, carnivores and both large and small herbivores. The first mammals were introduced by early canoe voyagers of the Pacific more than 1,000 years ago. The discovery of the Hawaiian Islands by Cook in 1778, like many other islands of the Pacific, marked the second wave of introductions of many hoofed animals for beasts of burden, milk, hides and meat as well as small predators to keep an assortment of stowaway rodents at bay.
Rapid ecological degradation ensued and whole groups of endemic plants and animals suffered extinctions, including virtually all flightless birds, and roughly nine percent of all Hawaiian flora. After a century of settlement by westerners, the concept of eradicating non-native species came about as a solution to primarily agricultural, public health, or economic problems, and only more recently to solve ecological problems. Reversing the devastating effects of alien mammals has proven to be difficult, but limited successes have resulted in the dramatic recovery of native biota.
Mammals General Overview
Most of the isolated islands of the Pacific existed for tens of millions of years in the absence of terrestrial mammals except for bats, which were able to fly over vast oceans and establish themselves. The first human colonists of these islands brought with them domestic pigs (Sus scrofa) from island southeast Asia and Polynesian rats (Rattus exulans). European colonists brought an assortment of other mammals with them nearly 1,000 years later, including domestic goats (Capra hircus), sheep (Ovis aries), cattle (Bos taurus), other types of wild and domestic pigs, cats (Felis catus), rabbits (Oryctolagus cuniculus), rats (R. rattus and R. norvegicus), and mice (Mus musculus). In the absence of natural predators and competitors, these species became abundant on nearly every island, which caused rapid ecological degradation. Native plants of the islands were poorly defended against the newly established herbivores, and native wildlife were naïve to tree-climbing predators with teeth. Species which had never been previously domesticated such as axis deer (Axis axis), European mouflon sheep (O. musimon), and mongooses (Herpestes javanicus) were brought to the islands later and proved to be particularly challenging to manage. Diseases associated with introduced mammals such as toxoplasmosis (Toxoplasma gondii), bovine tuberculosis (Mycobacterium bovis), and bubonic plague (Yersinia pestis) have all caused major problems for wildlife, livestock, and human health in Hawai‘i. Invasive mammals have caused the decline and extinction of numerous native plants and animals, but researchers and land managers have developed progressively more effective strategies for managing these species, allowing the recovery and restoration of native species in increasingly larger natural areas.
Small Mammal/Toxoplasmosis Overview
Many factors have contributed to the decline and extinction of birds in Hawai‘i, not the least of which has been introduced mammalian predators like rats, mongooses, and cats. These predators take eggs, kill nestlings, or nesting adults, but are also sources of diseases that kill birds. One such disease known as toxoplasmosis can cause severe developmental disabilities and occasional mortality in humans but can also have lethal consequences for marine mammals. The infectious agent of the disease, Toxoplasma gondii, is a protozoan, a single-celled organism which behaves like an animal. It is considered a parasite, causing infection directly rather than by producing toxins. It is a zoonosis because it is a disease of animals that can also be transmitted to humans. Only cats –regardless of whether they are domestic or wild species– can support sexual reproduction of this parasite, and thereby serve as the definitive host of the disease. Any other warm-blooded animal, most commonly rodents, can also carry the parasite but can only serve as an intermediate host. Intermediate hosts of the parasite and may sometimes be consumed by people, leading to infection. Known intermediate hosts include feral pigs (Sus scrofa) and mouflon sheep (Ovis musimon), both popular game mammals in Hawai‘i. Birds can also be intermediate hosts, and populations that have been infected and killed by T. gondii include the critically endangered ‘Alalā (Corvus hawaiiensis), the endangered Nēnē (Branta sandvicensis), Red-footed Booby (Sula sula), and Erckel’s Francolin (Pternistis erckelii), a common gamebird. Flowing water may transport T. gondii oocysts –hardy, thick-walled, environmentally resistant spores– in runoff from land to streams and then into marine environments. Thus, T. gondii represents a land-based pathogen that can pollute nearshore marine ecosystems and infect a wide variety of animals in this environment including whales, seals dolphins, and sea otters. The leading cause of death of the endangered Hawaiian monk seal (Monachus schauinslandi) is now known to be T. gondii infection. Many aspects of T. gondii are poorly understood, but current research may soon lead to more effective management strategies to protect native wildlife from both toxoplasmosis and predation.
Below are publications associated with this project.
The risk of rodent introductions from shipwrecks to seabirds on Aleutian and Bering Sea islands
Accidental introductions of rodents present one of the greatest threats to indigenous island biota, especially seabirds. On uninhabited remote islands, such introductions are likely to come from shipwrecks. Here we use a comprehensive database of shipwrecks in Western Alaska to model the frequency of shipwrecks per Aleutian and Bering Sea island, taken as a proxy for the threat of rodent introduct
Biology and impacts of Pacific Islands invasive species. 14. Sus scrofa the feral pig (Artiodactyla: Suidae)
Feral goats and sheep
Monitoring eradication of European mouflon sheep from the Kahuku Unit of Hawai‘i Volcanoes National Park
Conversion of native terrestrial ecosystems in Hawai‘i to novel grazing systems: a review
Federal collaboration in science for invasive mammal management in U.S. National Parks and Wildlife Refuges of the Pacific Islands
A tour de force by Hawaii’s invasive mammals: Establishment, takeover, and ecosystem restoration through eradication
Changes in habitat use and distribution of mouflon in the Kahuku Unit of Hawai‘i Volcanoes National Park
Abundance, distribution, and removals of feral pigs at Big Island National Wildlife Refuge Complex 2010–2015
Evaluating detection and monitoring tools for incipient and relictual non-native ungulate populations
Home range use and movement patterns of non-native feral goats in a tropical island montane dry landscape
Vegetation and non-native ungulate monitoring at the Big Island National Wildlife Refuge Complex 2010–2014.
Below are partners associated with this project.