This article is a study on the dietary shift of black rats on Surprise Island, New Caledonia and their impact on the ecosystem in the presence and absence of breeding seabirds.
The Key Biodiversity Areas and Important Bird Areas (KBA's
& IBA's) approach is a simple, effective means of
implementing the protected areas elements of the Convention of Biological Diversity (CBD). KBAs and IBAs are places of
international importance for the conservation of biological diversity through protected areas and other governance mechanisms.
Over the last four decades the eradication of rats from islands around New Zealand has moved from accidental eradication following the exploratory use of baits for rat control to carefully planned complex eradications of rats and cats (Feliscatus) on large islands.
During the 1970's village people in the Temotu province of the Solomon Islands complained to Provincial and Central Government authorities about rat damage to garden and plantation crops and household commodities.
Several aspects of the ecology of Rattus exulans are reviewed in an effort to collate a large proportion of the widely scattered literature relating to the species. Subspecific relationships are discussed to illustrate the early confusion regarding taxonomic position. Literature convening R. exulans geographic distribution, habitat, nutrition, reproduction, movements, and competition with other species of Rattus, is reviewed and discussed.
The black rat, roof rat, or ship rat (Rattus rattus L.) is among the most widespread invasive vertebrates on islands and continents, and it is nearly ubiquitous on Pacific islands from the equatorial tropics to approximately 55 degrees latitude north and south. It survives well in human-dominated environments, natural areas, and islands where humans are not present. Rattus rattus is typically the most common invasive rodent in insular forests. Few vertebrates are more problematic to island biota and human livelihoods than R. rattus; it is well known to damage crops and stored foods, kill native species, and serve as a vector for human diseases. Rattus rattus is an omnivore, yet fruit and seed generally dominate its diet, and prey items from the ground to the canopy are commonly at risk and exploited as a result of the prominent arboreal activity of R. rattus. Here we review the biology of this invasive species and its impacts on humans and the insular plants and animals in the Pacific. We also describe some of the past management practices used to control R. rattus populations on islands they have invaded.
Breeding success of 5 Corys shearwater Calonectris diomedea sub-colonies of Lavezzu Island (Lavezzi Archipelago, Corsica) was checked annually for 25 consecutive years from 1979 to 2004. Between 1989 and 1994, 4 ship rat Rattus rattus controls were performed in several subcolonies. In November 2000, rats were eradicated from Lavezzu Island and its 16 peripheral islets (85 ha) using traps then toxic baits. We compare cost (number of person-hours required in the field) and benefit (Corys shearwater breeding success) of control and eradication. The average breeding success doubled when rats were controlled or eradicated (0.82) compared to the situation without rat management (0.45). Moreover, the average breeding success after eradication (0.86) was significantly (11%) higher than after rat controls (0.75). Furthermore, the great variation in breeding success recorded among sub-colonies both with and without rat control declined dramatically after eradication, suggesting that rats had a major impact on breeding success. The estimated effort needed to perform eradication and checking of the permanent bait-station system during the year following eradication was 1360 person-hours. In contrast, rat control was estimated to require 240 or 1440 person-hours per year when implemented by trained and untrained staff, respectively. Within 6 yr, eradication cost is lower than control cost performed by untrained staff and confers several ecological advantages on more ecosystem components than Corys shearwater alone. Improved eradication tools such as hand or aerial broadcasting of toxic baits instead of the fairly labour-intensive eradication strategy we used would dramatically increase the economic advantage of eradication vs. control. Therefore, when feasible, we recommend eradication rather than control of non-native rat populations. Nevertheless, control remains a useful management tool when eradication is not practicable.
Rat eradication has become a common conservation intervention in island ecosystems and its effectiveness in protecting native vertebrates is increasingly well documented. Yet, the impacts of rat eradication on plant communities remain poorly understood. Here we compare native and non-native tree and palm seedling abundance before and after eradication of invasive rats (Rattus Rattus) from Palmyra Atoll, Line Islands, Central Pacific Ocean. Overall, seedling recruitment increased for five of the six native trees species examined. While pre-eradication monitoring found no seedlings of Pisonia grandis, a dominant tree species that is important throughout the Pacific region, post-eradication monitoring documented a notable recruitment event immediately following eradication, with up to 688 individual P. grandis seedlings per 100m2 recorded one month post-eradication. Two other locally rare native trees with no observed recruitment in pre-eradication surveys had recruitment
post-rat eradication. However, we also found, by five years post-eradication, a 13-fold increase in recruitment of the naturalized and range-expanding coconut palm Cocos nucifera. Our results emphasize the strong effects that a rat eradication can have on tree recruitment with expected long-term effects on canopy composition. Rat eradication released nonnative C. nucifera, likely with long-term implications for community composition, potentially necessitating future management interventions. Eradication, nevertheless, greatly benefited recruitment of native tree species. If this pattern persists over time, we expect long-term benefits for flora and fauna dependent on these native species.
Islands house a majority of the worlds biodiversity and are thus critical for biodiversity conservation. Seabird nesting colonies provide nutrients that are integral to maintain island biodiversity and ecosystem function. Invasive rats destroy seabird colonies and thus the island ecosystems that depend on seabird-derived nutrients. After rat eradication, it is unclear how long ecosystem recovery may take, although some speculate on the order of centuries. I looked at ecosystem recovery along a chronosequence of islands that had 1222 years to recover following rat eradication. I show that soil, plant, and spider marine-derived nitrogen levels and C:N ratios take mere decades to recover even after centuries-long rat invasion. Moreover, active seabird restoration could speed recovery even further, giving much hope to quickly conserve many endemic species on islands worldwide.
Desecheo Island supports important populations of plants, as well as animals found nowhere else in the world such as the Desecheo Anole, Desecheo Ameiva, and Desecheo Dwarf Gecko. Before the introduction of invasive rats, the island hosted large colonies of breeding seabirds, including the worlds largest Brown Booby colony and an important Red-footed Booby colony. But, due to the destruction of native vegetation and predation on eggs and chicks by these invasive rats, seabirds no longer nest on Desecheo and many plants and animals are threatened. Island Conservation and the U.S. Fish and Wildlife Service are working together to remove invasive rats from Desecheo Island. With the island free of invasive species, native plants and animals will once again be able to thrive in their natural habitat. Coral reefs in the Marine Reserve surrounding Desecheo (managed by the Department of Natural and Environmental Resources) are also expected to benefit from the islands restoration; increased vegetation will reduce soil erosion into the sea, and the seabirds will provide valuable nutrients to the adjacent marine ecosystems.
